I have a '87 Deville and when you use climate control this light comes on (coolant temp fan).I know it isn't overheating.It does this whether engine is cold or operating temp..Also the heat doesn't
seem to heat.I'm wondering if my problem could be the sensor in the grill(ambient air sensor?).
Also I have replaced both fans and control unit by the core support.Any suggestions would be appreciated. My car has the 4.1L V8 and fwd.

 

Hey 87:: A good thing to take a look at is the air mix door.This was a problem for me with it not heating. Take the glovebox liner out and the air mix chamber is in behind it.You will see a black cover, snap it out it of it's position and then you can see it and a small circuit board in there. Run the heat and air through it's paces and see if the door is going from closed one side and then to closed the other side. You may have to free up the door hinge with WD40 and put your hand in there and work it back and forth. The hinge becomes rusty with all the condensation in the chamber.Hope this helps.

 

Thanks for the info ,I'llcheck that hinge.I've had this car for several years and never knew there was a Cadillac forum.It's great to see people share
knowledge.