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ctjstr · 10-09-2008, 01:02 PM

Once again I find myself in need of help. This time its the thermostatically controlled fan that draws air through the transmission cooler on the side of the bus. That thermostat, or some related component has failed, causing the fan to run continuously, whether the engine is running or not, hot or cold. The only way to shut the fan off is to crawl under the bus and unplug it. I've crawled all over that transmission and simply cannot find the thermostat or any connection that feeds it. Unfortunately, the wiring harness to the fan disappears in a giant wire loom and I can't tell where it ends.

Anyone got any ideas where to start looking for the thermostat or whatever else might be the culprit? I have a suspicion that the circuit might run up through a relay, but if so, I'm not sure which relay it might be.

Thanks in advance.

ctjstr · 10-09-2008, 01:02 PM

Once again I find myself in need of help. This time its the thermostatically controlled fan that draws air through the transmission cooler on the side of the bus. That thermostat, or some related component has failed, causing the fan to run continuously, whether the engine is running or not, hot or cold. The only way to shut the fan off is to crawl under the bus and unplug it. I've crawled all over that transmission and simply cannot find the thermostat or any connection that feeds it. Unfortunately, the wiring harness to the fan disappears in a giant wire loom and I can't tell where it ends.

Anyone got any ideas where to start looking for the thermostat or whatever else might be the culprit? I have a suspicion that the circuit might run up through a relay, but if so, I'm not sure which relay it might be.

Thanks in advance.

Our Time · 10-09-2008, 02:30 PM

As I understaand the operation, the fan is controlled by the engine computor (ECM). You will most likely need a Cummins dealer to troubleshoot for you.

ctjstr · 10-09-2008, 06:29 PM

I think that's true for the new models, but these older units don't have an ecu in the same sense that the new stuff does. Monaco suggested a relay, but I'm having trouble figuring which one.

AKBrick · 10-10-2008, 05:50 AM

I'm sure that this is probably completely unrelated but.... After driving the coach (and yes the transmission fluid is hot), I shut down the engine to put out the slides. Then when I have to get rid of the air and put down the jacks I have to turn the key back on to the "accesory" position. I found that the transmission cooler fan also comes back on to continue cooling the fluid after being shut down for a few minutes. So anywaaaaay...the transmission fan is deffinately hooked up to the ignition switch somewhere. I guess the question is "where" on that system.

The first time we leveled the coach I went outside to watch the automatic jacks do their thing, I sort of freaked out a little bit because I heard the fan running and didn't know what it was. I quickly figured it out and my blood pressure went back to normal.

The only "lame" question I have is, was your key on "accesory" when you checked the fan? It comes on even when the transmission fluid is totally cool? Hmmmmmm....

Good luck,

AKBrick

ctjstr · 10-10-2008, 05:21 PM

I'm not sure mine is hooked through ignition, although I suppose its possible. In its current state, its powered all the time, ignition on/off/accessory even with the key out. I'm still searching for and through various relays and solonoids to see if I can find the culprit.
thanks for the suggestions though.