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Cadillac Repair/Blower Motor Control Module Test

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Expert: - 5/29/2009


Question
Can you tell me how to test a Blower Motor Control Module ?

I am not very handy but I can follow step-by-step instructions very well.

Thanks for your help.

Ray

Answer
Hello Ray,

You did not state the reason for testing it. Did you check all the fuses. You didn't state the make and model of the vehicle. Some Cadillacs come with more than one fuse box. You need to look at the owners manual to determine the amount of fuse box locations as well as where the blower fuse is located.

The only reason for the printed circuit computer board for the heater blower module was to control speeds. A very overpriced piece that was known for common failure for 25 years and yet Cadillac continued to use the module.

Common problems associated with the module--Fan continues to run with ignition off or no blower at all.

At any given time when visiting a Cadillac dealership there would be 2 or 3 Cadillacs with the hood up getting the module changed.

To test the module, if you have the ignition on with the heater or A/c on to max, go under the hood to the module. Check power going in with a meter or test light. If there is power going in and no power at the blower, you need a module that will set you back hundreds of dollars for something that is just due for imminent failure again.

Cadillac made a good a good car, but they had their quirks. Many of their engines were junk off the line and came with a factory knock. The HT 4.1, 4.5 and 4.9 were either good or problems from new. The northstar was known for eating oil. As I stated, another very common problem was the heater blower module.


Rob  

Cadillac Repair

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Rob Painter

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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?

Experience

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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