electric engine compartment fans

[Mike Groves]

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

[Doug Allman]

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.

[Edward Buker]

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

[Steve Huber Co-Admin]

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

[Edward Buker]

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

[Edward Buker]

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

[Michael Rump]

Ed,
My relay part number is 25530904, same as yours.
Regards,

[Edward Buker]

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

[Dick Simonis]

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

[Edward Buker]

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

[Edward Buker]

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

[Edward Buker]

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

[Edward Buker]

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

[Jerald Cate]

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