BAC Forum
General Boards => Technical Support => Topic started by: Doug Allman on May 27, 2016, 01:54:21 PM
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I have two electric fans mounted on the engine compartment cover. I have never heard the fans run but know they are free on the bearings. Had same type on our Contessa.
I am wondering if there is a thermostat somewhere that controls these fans to come on when heat is high enough after you stop to cool the engine compartment? I have followed the wiring until it goes out of sight to no avail. Anyone have info on this? All fuses I am aware of are good. Connections at fans are good.
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I found this using the search function. My search yielded several threads.
http://beaveramb.org/forum/index.php/topic,990.msg5972.html#msg5972
BTW, our coach has the rear hatch cooling fans and I have heard them running after stopping, but only a few times. I cannot hear them from inside the coach OR they have not been on when I was in the bedroom. The only times I heard those fans running was immediately after stopping AND when I went outside to the rear of the coach.
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I also have these and have been wondering what activates them. I have never seen them run. Later in the month I'll be at BCS and I'll ask them.
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Because of my curiosity I have been near the engine compartment as soon as I could after we stop at a rest area in the summer. Same for when we stop for the day in a rest area. I have never heard the fans run. Our water temp is usually around 188- 192 during summer driving and I can feel the heat from the CAT under the blanket and sheet in the bed.
If they are there they ought to run. How is the question. I remember opening the engine compartment on the Contessa numerous times to let cooler air in when we stopped out west on a very warm night in a rest area.
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There is a relay timer in the electrical bay. Mine had failed on our coach, so I ran a wire to the battery bay and put a switch so I could operate the fan when I wanted it to run.
The relay is flat and mounted on the wall. I would send a picture but the coach was sold.
Hope this helps.
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Tom,
Is that the electrical bay under the driver seat? Anything you can remember about the exact location or the shape, color, size, or brand of the relay. I have always been curious about this fan set also. Mine also has never come on. Be nice to wire a manual switch into the side console if the relay has failed and it is this close.
Later Ed
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I found what I believe is the fan control relay etc. In the battery compartment up at the right side in the chassis battery area is a relay panel and looks exactly as it is shown in a drawing 2505886 that I have in my Marquis 2003 wiring diagrams book.
Sheet 1 of 2
Left side of drawing indicates (Cooling Fan) and on right side of drawing in the panel the lower right relay has a designation M and below the is CFR. Because I do not understand all I should if you look back at the left of the drawing at the (Cooling Fan) there is an M in the bottom of the top circle. Right above the (Cooling Fan) is the (Thermostat) which also has an M in the top circle.
Sheet 2 of 2
Two individual boxes showing multiple info
FH5 COOLING FAN RELAY, 30A FUSE bottom left of drawing
CFR COOLING FAN RELAY
In this box are 4 lines with end of each line showing Batt Power, Relay out fan, Batt Power, Thermostat
Am I correct in thinking that this relay is for both the thermostat and the fans so that the relay senses the heat and then turns on the fans.
If no one has these drawings I can take pictures and email to you if you need to review, with more knowledge about electrical than I.
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I found the electrical connections for the fans under the wire loom so I am going to do a 12v test on them to verify they work.
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Fans work just fine. Both the relays for what I think are the fan and the ECMR are the same Hella relay. Is there any way to test them without having high heat to trigger the thermostat and then the relay to the fans?
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Doug,
If you send me a photo of them I will see what I can figure out. I'll PM my email. Tom seemed to imply it was up front i thought but may be different years and configuration..
Later Ed
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Ed, that is where I first looked as I thought Tom was indicating this also and did not find so tried other locations. I sent drawings to you, if not clear enough let me know and I will retake.
Relays are $10.38 each so I think I will just order and see what happens when replaced. Wait to hear from you first however.
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Here a pic of what appears to be a button thermostat mounted in the overhead of my engine compartment. Looks pretty bad cosmetically but I need to jump it to find out if it's a problem.
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All,
The picture that Dick just posted is the snap thermostat that controls the fans. Once the thermostat is located, just jumper the
connectors to test the fans. I also installed a switch whereas I can use them as desired.
My thermostat was located in the engine compartment (side wall, road side).
Best regards,
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Dick and Doug,
Good find you two on the schematic (which are at best hard for the not so gifted like myself to figure out) and the button thermostat. Dick can you describe where that is exactly in the engine compartment ceiling.
So here is what I think is happening in the design. Going to the CFR (cooling fan relay) are connections for battery power, relay out to fan, battery power, and thermostat. This uses a common single pole single throw Bosch style relay. Battery power is supplied to one leg of the relay switch, the other leg of the switch goes to the fan. The relay coil that activates the switch has 12V power on one side and the other side is connected to the thermostat in the engine compartment that Dick found. I think the thermostat is in series with the relay coil and feeds the ground side to the relay coil. If that is so there should be 12V on one side of the thermostat and the other side should go to ground.
If you jumper that thermostat Dick see if the fans start. If that is so, my suspicion is that the relay version they chose has no diode across the coil and that inductive kickback kills the thermostat contacts over a short period of time. I say that because the relays are quite reliable and so many of us have no functional fans so there must be a design flaw in the thermostat side.
The other possibility is the thermostat itself is junk. Both of these issues can be resolved fairly easily. A diode could be installed across the thermostat and a better thermostat by design can be sorted out.
Dick or Doug if you get a chance jumper that thermostat and let me know what happens. In case I am wrong on the design do just a very quick jumper across. There may be a little arc, that would be normal. I am pretty sure that this is the design and the fans should start.
Later Ed
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Anyone have a PN or cut in cut out temp for that snap thermostat Michael and Dick pointed us to?
Later Ed
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Ed. just looking at mine briefly, it appears the thermostat is directly in line with the fans and carrying full amperage. Two wires from the fan and the thermostat is series with the white wire which than goes to ????. No idea what the temp rating is but if I get time when we're done packing I may pull it out and look or at least try a jumper.
One thing that bothers me is that these button T-stats tend to be surface reading and it's screwed tight to piece of wood. That being the case it would read the temp of the wood not the air.
Still a bit of mystery.
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Ed,
Opens at 150F and closes at 135F.
Found the following Redi-temp thermostats that are close;
3455RC-100-229 Open at 155°F Close at 125°F
3455RC-100-230 Open at 165°F Close at 135°F
Regards,
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Dick,
If that is the case no wonder it fails, really bad design. That may make the relay an ignition relay that will only be on when the ignition is off maybe, just cooling once you shut down? Anyone have the original design working, is it interlocked to the ignition? We could add a relay if the fan load is fed through the thermostat.
Michael,
I think the high end would be the close and the low end the open? This seems like quite high values to me, does it work well with that range? I just put an order in for one of these adjustable versions up to 130F anticipating that mine has failed.
http://www.amazon.com/Emerson-3F05-1-Adjustable-Snap-Control/dp/B000PY7T7I?ie=UTF8&psc=1&redirect=true&ref_=oh_aui_detailpage_o00_s00
Later Ed
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I totally agree the design appears lacking but the other question is what is the power source. It must come off some protected circuit whether is ign on/off or either. I need to stick my head in the battery and electrical bays and see if there is a clue.
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Dick,
Doug Allman sent me a cryptic schematic and there is a relay on the board in the battery compartment that seems to control this that I attempted to describe in my prior post. It is the relay on the lower right of the board in the battery compartment. If labeled it would be CFR.
Later Ed
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I located this device in the engine compartment on the DS wall above the engine fan assembly. I haven't had any luck locating a data sheet or supplier source, maybe some of you other guys are better parts chasers.
Bruce Cate
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Bruce,
I wasn't able to locate the part #. Give Ken a call at BCS as he may know the correct temp range for the fan control snap disk thermostat.
Steve
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Print attached.
Regards,
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Thanks Mike. I missed your post of the temps.
Bruce, here is a replacement for the fan control thermostat based on the temps on the schematic. http://www.supplyhouse.com/White-Rodgers-3F01-150-3-4-Snap-Disc-Fan-Control-Cut-In-150-Degrees-F-Cut-Out-130-Degrees-F-14695000-p
The circuit as designed will cause the fans are run any time the engine compartment is 150F or higher, ignition on or not. It's not clear to me how effective they are when the engine is running and one is driving down the road. Addition of another relay between the thermostat and GND will enable the fans to start and run when the ignition is off and the temp is above 150 to exhaust the built up heat in the engine compartment. See attachment. Just a thought..
Steve
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These fans were wired in the original Beaver built coaches, pre 1994, so that they turned on with the ignition switch and when the ignition was turned off, a timer was activated that powered the fans for an additional 30 minutes after ignition shutdown.
The bed was directly above the engine in all of these coaches with very little insulation below the mattress, and since heat soak in the mattress was such a problem, no thermostat was ever used, just the timer.
Gerald
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Mike,
Now that is a schematic I can live with, old school :-)
So there is no magic here, it is about as expected. The coil of the relay is energized by the thermostat turning on. The relay contacts close and handle the motor load through the fuse from the battery as a supply, so there is no ignition interlock. The only thing missing is a suppression diode across the relay coil. Without that you will get arcing and erosion pitting of the thermostat contacts, as they open, when the relay coil field collapses. That is a likely source of our fails. Should be able to get a relay that fits with that diode protection built in. If the hand notation on the schematic I got from Doug is correct the relay is a Hella 87411 which at least has a suppression resister across the coil which is a help, a diode would be better.
Later Ed
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Steve,
Added circuit looks like a good idea if the fans indeed run while cruising down the road. My sense is you would not get to 150 degrees while moving at any reasonable speed. Since mine has never worked i really do not know. Anyone have a sense how often this kicks on and has a working version?
Later Ed
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Ed,
You are probably right, depending on location of the thermostat, although some of the newer engines are running pretty hot so overall compartment heat also increases. In any case, I think it would advantageous to have fans start exhausting immediately on shutdown rather than waiting for temp to reach 150. Gerald's comment re a timer is also an approach but it seems to me temperature would be more effective. Only downside with temperature trigger is that you would probably increase battery drain.
Steve
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I did find the thermostat in my coach. It is on the upper wall of the engine compartment behind the coolant tank and very close to being right above the turbo. about 15" above the turbo.
Those numbers on the drawing are from my Hella relays. Would we be able to change to a different relay so that we would not continue to loose the relay ?
Also only get cooling after the coach has stopped. If we go to that use I would believe we would want to cool down to somewhere near or below 100 degrees. We would not necessarily need a high and low just a relay that would keep fans running until below the set temp. The mattress even with some insulation in the later model coach's still gets very warm, in the summer travel.
Looks like I am glad I brought this up. Could help a lot of us. Thanks to all input so far.
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Doug,
It is a good post, this fan thing has been a a bit of a mystery to most of us as to where things are and how it is supposed to work. You do need a "window" of on off temp with a sensor or it would just keep cycling. Looks like about 20 degrees on most of these thermostats.
Steve,
I do like the info that Gerald passed along and the old way may have been better. Best of both worlds...Seems like a 110 F cut off thermostat in series with a 30 minute cycle timer that is initiated when the ignition is in the off state would be a good way to go. Runs 30 minutes only if over 110F and only for 30 minutes but a settable timer module might be better given you could set it as you wanted. Could be wired in and live right in the rear closet area given the thermostat is below it.
Later Ed
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What Gerald describes is what my '99 Marquis has. The power comes from a post on the alternator, and the fan runs while the ignition key is on (after starting the engine) and shuts down 30 minutes after the coach is stopped.
Mike
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ED, do you know if we can get a relay with a diode in it to protect contacts? I want to get this back together as I am going to travel on June 20th and would like to see if it works then before we head out in August for 6 weeks travel.
Because the fans work I am making assumption the one or possibly both of the relays for this is bad. I do not know if the snap thermostat would be bad. Can you test these relays?
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Doug,
The relays are pretty reliable and I am not sure what is in there now but I will take a look. If you get a chance to read numbers and brand on yours that would help us understand if it has a diode, resistor, or nothing for suppression. It may not be what is in mine.
My guess is that the snap thermostat gives up over time. Jumper across the snap thermostat with a wire and see if the fans come on. if they do the relay is working and what you can do is buy a manual switch and install it to replace the snap thermostat for now and tie wrap it to the harness back there in a convenient place. You can then manually turn on the fans for however long you want when you come into a campground. The alternative is to replace the snap thermostat, I would possibly add the switch option also in parallel to the snap, could be handy at times.
Later Ed
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Ed, my relays are the Hella 87412. I will jumper across the snap thermostat this afternoon and let you know results.
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Doug,
My relay is a Hella 25530904 which is the same relay with a GM number. They are superseded by Hella Number H877411. This seems to cross again to a Hella 007794301 but I cannot assure these crosses. Auto parts store like NAPA should be able to verify a cross from your original relay part number if you need one. These are quite common versions so it should not be much trouble.
http://www.amazon.com/HELLA-007794301-Weatherproof-Relay-Bracket/dp/B003TEO9GU/ref=sr_1_4?ie=UTF8&qid=1464635578&sr=8-4&keywords=hella+relay
I looked at a Hella catalogue and they do not make a skirted weather resistant version with a diode. My suspicion is these are made to be outside for lights and horns and things that do not need the best coil suppression. The relay at least has a suppression resistor. One thing I noticed is that the snap thermostat on mine is physically tiny and therefor probably has tiny contacts. My plan has been to buy a physically larger snap thermostat and start there. I ordered a 130 degree max adjustable one with a 20 degree on off window and we will see if that works well. I should be able to turn the adjustment down to test it if it is warm out....we will see, may need higher then 130 degrees based on Steve's info.
You could also place a 1N4007 across the snap thermostat crimp connectors with the cathode side (lined end of the diode) toward the + lead coming from the relay and the other side toward ground. That should pass the relay coil flyback effect to ground. They are inexpensive, just insulate the leads with shrink tube where needed if you decide to do this. A bigger snap thermostat may just do it.
http://www.amazon.com/1N4007-Rectifier-Arduino-Snubber-Flyback/dp/B00LUJFFAU/ref=sr_1_1?s=industrial&ie=UTF8&qid=1464631405&sr=1-1&keywords=rectifier+diode+1n4007
Later Ed
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Ed, how about this one with a 900 sec off delay?
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Dick,
I thought about that but it would run just 15 minutes and it ignores temperature, one in the link below. In looking for a time delay relay most are for lights or glow plugs and are not like 20 to 40 minutes. That sent me looking at little timer boards but they are not really weatherproof and would not like the engine compartment.
http://www.delcity.net/store/Time-Delay-Relay/p_804415.h_811050.t_1.r_IF3003?utm_source=bing&utm_medium=cpc&utm_term={keyword}&utm_content=Ad+group+#1&utm_campaign=Shopping+-+PLA%27s%28BSC%29&utm_keywordmatchtype={MatchType}&mkwid=8TgfXoca&crid=11472933143
A timer would run in the winter when you shut down and sometimes a warmer bed over the engine is nice. I think having the fan run longer when it is really hot, less when it is moderate, and not at all when it is chilly is what I think we are after. So I am back on a thermostat control. I plan on playing a bit and ordered an adjustable one like this. Range is 90-130F, close on rise, 20 degree difference for shut down. I think it needs contact with metal and a little thermal mass in the engine compartment to sense real heating and cooling. I was thinking of a little copper plate on a piece of the steel frame. Not sure where yet.....still thinking a bit, and like most things will require some playing around.
When we hear from Doug we will know if the thermostat is the likely culprit...
Later Ed
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Ed, jumpered the thermostat three ways, as coach sits off, with key on accessory, with key in on position and no fans in any mode. I know fans will run with 12v power when disconnected from the wiring to the coach.
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Ed, should have mentioned that I agree with your winter, cool weather and warm weather traveling for when to let heat build in compartment and when we want to get rid of heat in compartment. Maybe the switch process is the simplest fix so you can do as you wish when you wish. Would not be terribly difficult to get a switch to a location each was happy with in their respective coach.
I would assume you would remove the thermostat and use that location to start your wiring to the new switch location.
When I jumped thermostat made me believe I must have a bad relay or relays. Correct?
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Doug,
Relay, fuse, contacts, or wiring.....I would replace the relay next after checking the fuse. I am not exactly sure if the fuse is on that board with the relays or if it is separate. In the schematic that Steve showed the ignition relay mod on, it appears to be one those the semi sealed screw tab fuse holders coming from the battery.
Yes I would start the wiring from the thermostat and probably take the switch harness up into the closet and mount the switch in a convenient spot. If you had a working thermostat and were doing this once, you could bring up 3 wires and put a switch in parallel with the thermostat that bypasses it to override the thermostat and turn the fan on when you want. One switch in series to turn the fan off if you like. If you were happy with the thermostat handling of this then just leave the series one on and the parallel one off. Simple option just one switch and no thermostat...
On the diagram it says battery power from S4 which is on the lower left of the board with the relay but no idea what S4 is from the diagram. Anyone know where the fuse for the fan circuit is? My guess is whatever is failing is likely to be common to most of us that do not have working fans. We should be able to make this system more reliable. Maybe the snap thermostats are doing the job.
One more thought, the diagram shows the fuse at 25 amps, not sure what the fans actually pull for current. We may find that the board/relay socket wiring, some connection is just not up to handling 10 to 20 amps of motor load and have to take this circuit off the board and mount some better components on the sidewall of the battery compartment....hope not.
Later Ed
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I had noticed in Mike's post that he indicated the fuse holder was mounted at the alternator. I had remembered one there, so I went out and checked it out. There is one there on mine with a label saying engine fan. I checked the fuse and it was good but was a 5 amp fuse. Hard to believe those two fans would be pulling just two to three amps as you would size the fuse to be roughly twice the load for DC motors. The schematic had a 25 amp fuse listed so the mystery continues. With the battery switches on and ignition off I had just a couple of tenths of a volt so no battery connection is being made to the fuse. Given its location it may come after the relay, really not sure at this point. Mike you have a working system, if you have a meter can you pull the fuse and check each sides of the fuse socket to ground and see if you have 12V to ground on either side....that would help. Ground probe can be on the alternator metal housing.
Later Ed
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Ed, any chance that the fuse on the alternator is what is supplying power to the relay coil?? Kind of a convoluted way to start the fans when the engine is running??
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Ed,
Your right about there having to be another fuse in-line somewhere. I put an amp meter on my fans the other day and had about 26 amps startup current and about 16 amps run current.
Bruce
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Jerald,
Another clue, thanks for letting us know. Clearly there are still some mysteries left in how these fans are powered and operate. Your current readings would indicate that the 25 amp fuse in the schematic is real, now where it hides nobody knows yet....
Dick,
That is possible, obviously the fans do not run using a 5 amp fuse alone based on Jerald's measurements. The 5 amp fuse at the alternator is a mystery, it may be physically mounted there on the alternator just as a holder given you have access to it from the rear engine hatch. Between all of our pieces of the puzzle we will get there...
Later Ed
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I had a few moments to look at the board arrangement in the battery compartment this morning that contains the relay for the fan control. Next to that relay is a fuse holder, I pulled both the relay and the fuse. The fuse was a 30 amp and it was open. I just started looking at the relay and will be checking that out. The spec on the schematic was 25 amps, maybe those blew and went to 30 amps and now that may be marginal for the fan set, not sure. Good news was all of the contacts were clean and in good shape. May still add a little corrosion X.
Message here, check that fuse next to the relay on the lower right of the board...I think without a doubt a manual switch (reasonably weatherproof if it resides in the engine bay) should be put in parallel with the snap thermostat so you can test this circuits operation anytime without having to heat the back up. It may be best to run the wires up into the closet for manual operation also if you are going to the trouble anyway.
Later Ed
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Ed,
Saw your post this morning. Unless I start the engine (we're sitting comfortably at our lot on the Oregon coast) I wouldn't be able to measure anything I don't think because the fans don't start up unless the engine is running. When the engine is running I am not happy about working back there due to my lack of insurance.
Sorry, not to be contributing. My fan eventually stopped working so I replaced it with a new one of about the same size but I think it pulls a little more air through.
Mike
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ED, Just pulled out fuse next to my lower relay and it is also a 30amp blown fuse.
Replaced with 30amp fuse, jumpered across the thermostat and BINGO the fans come on strong. Fans came on with coach just sitting in its bay CAT not running or key turned to either position.
Obviously all relays work, thermostat works, fans work and with fuse that works (holds maybe) we will have to see if it works when it gets up to temperature and when and how that is regulated.
Thanks all for the input.
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Doug,
I bench tested my relay and it is fine, low contact resistance so that is not coming into play. Our experience is the same with the blown fuse issue.
Tell you what I plan on doing, given it is quite simple, and I think handy. I had added a piece of diamond plate aluminum on the left side of the engine compartment and mounted an extra overflow expansion jug for extra capacity on the left side. My wiring harness to the snap thermostat comes right next to that plate area down a vertical support. I should get the adjustable snap thermostat today.
I am going to make a little wiring harness, needs to be just a foot long or so, mount two switches on the diamond plate. One switch will be in parallel to the existing snap thermostat to bypass it, and the other switch will be in parallel but have the adjustable snap thermostat in series with it using some plug male and female connectors.
This will allow the existing hi temp thermostat to be used or switch in the adjustable snap thermostat at a lower setting if preferred, the second switch can be used to test the fan system manually or to turn the system on if desired. I decided to make the second thermostat plug-able so I can vary the mount location if need be to get the desired result.
Funny if all of us are sweating in the bedroom and riding around without an operational fan system due to a fuse :-) May still need some mods if the fuse keeps blowing...
Later Ed
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Ed,
Make sure you write up the cooling fan operating instructions for the new owner when you sell it or he/she will be back on the Forum asking us how to operate them. :) :)
Steve
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Mike,
Not a problem, we all help out when we can....
Steve, On/Off and Fan Temp HI/Low labels should do it (hopefully) :-)
Doug and anyone else following this thread....
I think we are still going to have fuse issues given we have not done anything to prevent this. If we do, a relatively simple cure would be to separate the two fan wiring looms and add a Bosch style relay in series with one of the fans on the plus lead, removing it as a load. They have weather sealed plugs and relay like the ones below that can be mounted in the engine or hatch area and tie wrapped to an existing harness.
https://www.amazon.com/HELLA-007794301-Weatherproof-Relay-Bracket/dp/B003TEO9GU?ie=UTF8&*Version*=1&*entries*=0
https://www.amazon.com/dp/B000VU9D0C/ref=pd_lpo_sbs_dp_ss_2?pf_rd_p=1944687762&pf_rd_s=lpo-top-stripe-1&pf_rd_t=201&pf_rd_i=B003TEO9GU&pf_rd_m=ATVPDKIKX0DER&pf_rd_r=MWRGM0SWKT5CK21RSG9X
The plus lead that was coming to that second fan from the existing wiring would just be used to excite the added relay coil. You would then need to add a power lead coming from the alternator output with an inline 20 amp fuse to the switched contacts on the added relay that now feeds the second fan. I would replace the 30 amp fuse in the existing board with a 20 amp fuse and up it to 25 if you have a problem. Hope this helps.
Later Ed
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The latest....I spent most of the day yesterday with no success on my engine fan system. Every time I powered it up it would blow a fuse. The test on switch came in handy. I assume my snap thermostat is good, it is open at the current ambient temperatures. I bench tested the relay and it seemed good. I disconnected and ran the fans off of a 12V source and mine pull 7.5 and 8.5 amps, so about half the fuse value which is about right for a DC motor. I decided to buy a new relay in case there was a contact issue under load adding series resistance and that was my problem. I also checked all leads from the motors to ground in case the + lead was shorting within the motor to the frame and they were fine.....really scratching my head on this one so I slept on it.
I decided that there had to be a factory wiring issue or the relay output going to the fans was shorted to ground but I had measured that and it was good. In my case it looks like my coach was miswired from the factory or the original relay was changed to something with a different configuration. It would be a huge favor if a few of you could read the PN on the lower right plastic skirted relay on the epoxy potted board on the right of the battery compartment. The common versions are PN 25530904 , PN 87411, PN 87412, PN 87414. My PN was on the cover of the relay so you do not need to pull it to read it. On these relays pin 86 is a coil connection that comes out to the snap thermostat to ground. On my coach 86 goes to the fans instead and 87 goes through the snap to ground which sends the 30 amps to ground when the snap closes or my test switch is activated. This was a pretty obscure problem you would not expect to find. What I am looking for is if there was another relay PN version Beaver used that would match my wiring correctly. Thanks in advance.
Later Ed
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Ed,
My relay part number is 25530904, same as yours.
Regards,
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Thanks Mike, appreciated. I guess I will go back out and rewire it unless another PN pops up soon and I will check out the diagram for it.
I can see how this can happen at the factory. All the wires are white and until it is activated by heat there is no way easy way to test this circuit. You do not know the fuse is blown unless you pull it. One would just assume that the compartment never gets hot enough....
I will post the mod with some photos when I am done.
Later Ed
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Ed, would you be so kind as to post a pic of the board with the relay and fuse. I've looking and all I found is a board with 2 relays and about 4-5 fuses.
Thanks.
Dick
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Dick,
That is the one with the two relays and 5 fuses on the right of the battery compartment. Bottom right relay runs the fan and the fuse is next to it.
Excuse the dirt, it is cleaner now after all this intimate time hanging out with this board and relay :-)
Later Ed
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This started out as an easy mod but my motorhome was miswired at the factory and therefor these fans have never run. I had assumed that there was some component flaw due to a possible design flaw causing so many of these systems not to work but the components seem sized properly and robust enough.
On mine the wire coming from relay terminal 87 that was supposed to go to the fans went to the snap thermostat and the terminal 86 that was supposed to connect the snap thermostat went to the fan. Any time the thermostat was activated it blew a fuse. It is not an easy troubleshoot first time around given you would not head in that direction unless it was the last resort.
If you end up repeatedly blowing fuses but the motors are good when you power them with another source I can walk you through how to check if you have been miswired also. If so you will have to cut and splice some wires in the back area to alter the current wiring.
Later Ed
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The Fan Mod:
This is actually a very easy mod that can be done all from the left side of the back engine hatch. My intent was to add an adjustable lower temp thermostat in parallel to the existing thermostat with a switch that allows it to be added in. Also a manual test switch that turns the system on anytime. If nothing else consider adding a manual switch just to be able to test and diagnose what might be wrong with this system. It is not easy to work on this system, or test it, if you have to wait for 150 degree heat to activate it.
What You Would Need To Do:
1. Find the current snap thermostat. It is located on the left ceiling of the engine compartment. On mine there was white tape on the harness identifying where the thermostat was located in the harness.(see photo)
2. Follow the wiring harness from that thermostat, which on mine runs down the metal post near the hatch on the left side of the engine bay.
3. Locate the two wires and expose them (see photo). I use a razor blade to trim a little insulation and solder the new wire harness connections onto the exposed area. You could cut and butt splice in the added wires also. Basically your new switch or switches will jumper these wires.
4. Sort out your switch location. You could just tie wrap a switch to the existing wire harness above or below what you just exposed if you want to keep it simple. I chose to mount my two switches on an aluminum panel and made a little harness and sealed the switch connections. (see photos) One switch just jumpers the two exposed wires, while the other switch does the same but has two spade lugs in one wire leg going to the switch (a break if you will) that can accept a timer connection or an alternate thermostat or whatever you like to activate the fans. Could be a wireless remote module with a FOB.
5. I mounted the adjustable thermostat that I added, on the vertical aluminum frame member to the left side of the opening near the top. (see photos) This thermostat can be set from 90 to 130F with a 20 degree offset turn off window.
If in practice for the current season the existing original snap thermostat is the right temp range then leave the switches off. If you want the fans to exhaust more heat and bring the temp down lower then you have with the original thermostat then turn on the switch for the second thermostat adjusting it to your liking. Seasonally, you can add it in or take it out, or manually run the fan if you like.
Hope this helps.
Later Ed
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One last follow up on the fan mod post. I pulled the coach out today, we washed it and I decided to run it a bit and check the fans out. The fans came on using the original thermostat and ran a good 45 minutes and the engine compartment was quite cool. Felt the original snap thermostat and it was under 100 degrees.
I found my snap is cutting in low and not opening back up when it is supposed to, so age has this thermostat out of calibration or it is the wrong one from the factory. My added variable thermostat I could not use given the original Snap thermostat was already closed. I will order a new one that Steve Huber pointed us to and change it out. While I am at it I will put a switch in series with it so I can just turn it off if it fails or I want to use the alternate thermostat. I had to pull the fuse today to shut the fans down. My saga continues, but almost there....
Later Ed
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I finally got around to checking my fans today and found they apparently have worked all along and I've just never heard them come on. The easiest way to test the system is with a heat gun, if you don't have access to one a hair dryer may work but it will take a lot longer since the nozzle is not as focused. I put the heat gun about 1" from the snap thermostat and the fans came on in less than 15 seconds. I also measured the temperature with an IR gun and it came on at about 190 degrees F. I let it cool down and the fans shut-off when the snap thermostat cooled to about 100 degrees F. Don't know why I didn't think of trying this earlier, I've only been retired for 2 years didn't realize I was getting that slow. Good luck.
Bruce