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Cadillac Repair/1997 Cadillac Deville


My A/C & heater isn't working.. It isn't blowing through the vents , floor , or , defrosting .. The blower is working. The compressor is working.. It's something stoping the A/C from blowing out ??? Can you help me please ? Thanks


Actually its not that big of deal if you understand the system. Locating might be challenging. All the mode doors are controlled by vacuum. For the air to come out the defroster, one mode door closes and another opens. If you go from defroster to max a/c mode door from defrost closes and another opens to send the air to center vents. The concept is now easy for you to understand.
This has been the same concept on GM cars going back to the 60s.
For you to find the mode doors you would have to remove what we call hush panels. They arre on the bottom of the dash hiding the wiring etc. Take the passener side and you will see the plumbing for the heater a/c and the mode doors.
You may have to buy a $20,00 hand vacuum pump for supplying vacuum to your rotary
control valve. You should be able to remove the heater control and you should see a bunch of vacuum lines in a circle. If you were to remove the vacuum assembly and apply vacuum to one of these lines, you would hear a mode door open or close.
Your problem could be as simple as a broken or disconnected hose feeding vacuum to the control unit from the computer or under the hood.
So as I said, knowing what is wrong is half the problem. The other half is location it.

You may have to go to eBay or Craig's to purchase a factory service manual for your make and model. I highly recommend because it will save you money on diagnoses in the future to because even for a novice, the diagnostic flow charts will walk you right through just about any problem, which means no guessing. A/c vacuum schematics are there as well!
I hope I helped you here. Let me know what you find. Good luck!

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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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