electric engine compartment fans

[Doug Allman]

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.

[David T. Richelderfer]

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.

[Dick Simonis]

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.

[Doug Allman]

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.

[Tom and Pam Brown]

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.

[Edward Buker]

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

[Doug Allman]

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.

[Doug Allman]

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.

[Doug Allman]

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?

[Edward Buker]

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

[Doug Allman]

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.

[Dick Simonis]

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.

[Michael Rump]

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,

[Edward Buker]

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

[Edward Buker]

Anyone have a PN or cut in cut out temp for that snap thermostat Michael and Dick pointed us to?

Later Ed