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Cadillac Repair/1991 Cadillac Deville Heater Blower Relay


QUESTION: My brother is restoring a 1991 Cadillac Deville, He cannot locate where on the car the Relay is. Please tell him where it is?

ANSWER: Hello,

You did not give the reason for the question. Is the blower running constsntly and running the car battery down? Ticles had issues and there weretwodifferent styles that Cadillac used. The ecm (computer) can contrl the motor speeds. The other style used a module at the passenger side fire wall under the hood with one wire leading from the module to the blower motor.

Very expensive to repair and you will only have high blower or off if you have to bypass.


---------- FOLLOW-UP ----------

QUESTION: The Heater Blower won't shut off even when the engine is turned off so yes it does run the battery down. My brother couldn't locate the Relay to this Heater Blower to see if it was bad or not. He has been a Mechanic all his life and was one in the Army. He is mostly self taught though.  So, my main question is where is the Relay located in the car that goes to the Heater Blower Motor.  He updated me and said in talking to another brother, self taught, they think the Resistor is bad and that also is expensive but he still hasn't found the location for the Relay.
I think this is great. I will send a question about my car.


This is so very common and the solution is not as simplistic as a relay. As stated in my previous answer, you either have a $300 noon-servicable module assembly on the passenger side under the hood or the problem is in the body control module depending on design.
Either the expensive replacements parts if they can be located or a tohgle can be placed under the dash connected to ignition power so the battery does not discharge like it does now.
Then a wire is run through anexisting grommet under tge hood. An in life fuse holder is used with a 30  amp fuse and connected to blower motor. This will give you high fan and off.
Rheostates will not work for blower speeds without starting the car on fire.

This was planned obsolecence on the part of Cadillac. I have dealt with this issue since 1982 just like the dealer.


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Rob Painter


Alarm system questions cannot be answered on this forum. These systems are not what I can answer. Without being physically at the vehicle and not knowing what kind of electrical service has been done on the vehicle, there is no possible way to give an accurate answer over the internet. My expertise is in Ignition/key based anti-theft systems. These issues include GM VATS (resistor chip in key blade) PASSLOCK (MRD)-ignition lock rotation based, no special ignition key and the PKIII Transponder (computer chip in key) systems. These systems are not alarm based and are integral with the starting of the engine. This is why I cannot diagnose alarm problems without physically looking at the vehicle: Alarm systems are a completely different annimal than ignition key/lock based anti-theft system. Many alarm questions come from vehicles 10 years old, and since older, many hands that had been involved over the years.I am an expert in all GM factory (ignition/key based)systems. Alarm system questions pose to many situations beyond my knowledge as to what has been done to the vehicle over the years. Some guy may have actually wired the stereo into the alarm system. Who knows? Over my past 30 years in vehicle wiring repair, I have seen unbelievable wiring disaters done by guys that consider themselves "mechanics." I have seen stereos and alarms intalled using surgical tape. I have seen modules burn up, un-fused circuits, wiring jambed between the doors and even lamp cord used for a starter kill. To answer alarm questions over the internet without examining the vehicle is like asking; What does it take to remove a dent?


Education/Credentials-ASE certified. 11 years with a GM dealer and 17 years with a repair facility dealing with only the repair of theft recovered vehicles.

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