4.1 with Radiator Fan Problem...

[CaddyManDan]

Hey Guys,

New owner of an '86 Deville here... So far, everything about the car is great (1 owner, 109k mi, perfect interior, and only $900!)

That is except for the radiator fans which seem to have stopped working. When the car sits at idle for too long the "Fan not working, Engine Overheat" warning light comes on until you get moving again and air gets moving through the engine compartment. Upon inspection, I've noticed the smaller one moves every now and then sort of slowly, and the large fan does not spin at all. I'm wondering if this is a common failure point of these cars and if so what you all think is probably the root of this? I'm thinking the relays are the issue and not the electric motors... I've also thought about somehow trying to manually hook the fans up to their power source so they will always run - has anybody done this? Any info is greatly appreciated.

Thanks!

[Ranger]

It has been so long since I had a 4.1 I don't remember much about it. I'd start by pulling the codes and checking the relays.

[86cadman]

I have the same car, but I've never really had a problem with the fans. Like Ranger said pull up the codes. (Off and Warmer buttons at the same time, and read the codes in the Fuel Data Center). Check the wires, it seems that these cars have electrical issues. However, like you said hard-wiring the fans to be always on does seem like a solution, however, I'm no mechanic so its just a guess.

[behind-bars]

Hard wiring h\fans has been done before, not sure where i saw it though

try key on engine off and pushing off and warmer, run through the codes then push econ. I want to say f85 will appear, then push and hold 'Hi" and it should force the fans to high speed, "lo" shuts them off.

I have similar problems where mine run all the time, thier is a part to replace that may fix it but I havent done it yet.


Here is my thread on the opposite problem , could be the same module
http://www.cadillacforums.com/forums...ime-4-9-a.html (Fan Runs all the time on 4.9, engine runs real cold)

[noahsdad]

You'll probably also have an F41 trouble code - Cooling fans problem. Hard wiring the fans is a cobble solution in my opinon. Once you start down that road with a Cadillac you're asking for trouble.

Your problem is almost certainly the coolant fans control module, located behind the left headlight on the radiator support panel. You can find it by tracing the wire harness back from the fans. It's about the size of a deck of cards, with a finned aluminum top. A common failure item on '85-'93 C-body DeVilles. I bought two of them at the local junkyard for $20.00 when mine went bad - one for a spare.

Do the override diagnostic as specified by behind-bars. If both fans run, replace the module. If only one fan runs, jumper the known good connector to the fan that doesn't run and try again. If fan #2 runs now, replace the module. If fan #2 doesn't run, the fan motor is bad.

[CaddyManDan]

thanks everyone for the responses, i acually plugged the connector from the small fan into the big fan and with the override it then worked, so from the looks of things its the module. im going to try and find a replacement. if anyone has any leads on guarenteed replacements let me know! thanks everyone, you all are super helpful.