87 Coupe DeVille Dash Fan Won't Shut Off

Hello,
I'm trying to help out gramp's. This car has all off 70K on it. It's a 4.1. Been dealer maintained since he bought it. I didn't have much time to troubleshoot as he told me the problem as I was leaving.

I had him hook the battery back up. Started it and tried to get the fan to shut down using the thermostat control. There's no off switch so that's about it. It did go to high though when I turned the AC on. I'll look into it more when I get back in town to visit. Just looking for ideas ahead of time. I figure he's probably just got a bad solenoid. I've never messed with thermostat control though...

Thanks in advance,
Mike

Wow!
My '87 Deville just started doing the same thing. The fan runs all the time, even with the key off and pulled from the switch!
Here's the fix: The problem is in the fan motor control module, which is located atop the same housing where the fan resides, about in the center of the firewall. You'll recognize it by the two electrical connectors running to it, one with three or four wires, the other with two. There are four bolts which connect this module to the housing.
The problem results from an open circuit caused when the transistorized electronics fail inside this blower motor speed control. They sometimes fail because the blower motors are drawing too many amps, but unless you've had other problems, it's likely just the controller module.
If you can find one, get a replacement from a junkyard. The new ones (if your dealer still has one) are about $150. My local yard sold me one for $40 and guaranteed it for 30 days. It's a simple unplug, unbolt, remove - then reverse the process to install. Your blower should work fine after that.
However, these things fail frequently. You may have to do this again someday.
Good luck! Gotta love those Cads!

Thanks Noahsdad,
I was about to give up on this thread.

I see you have 1 post. I appreciate you taking the time to register in order to reply.

I'll start checking the local yards and internet.

Have a good one....
Mike

Is The Replacement Process The Same On An 88' Sedan Deville?

Is The Replacement Process The Same On An 88' Sedan Deville?

Hi,
There seems to be several years of this model being used in different Cadi's. Haven't come across a reference list though. Best thing to do is pop your hood and l look for it. I'm told it's near the center of the fire wall and has a connector with purple wires.

Good luck,
Mike

Thanks, Will Do