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Cadillac Repair/Heater Not Working in 1993 Cadillac Sedan DeVille

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Expert: - 11/28/2009


Question
The heater in our 1993 Cadillac Sedan DeVille has stopped working (air flows properly but no heat).  Upon checking the coolant level, we found that it was down significantly (approx. 3 quarts).  Since then we have filled the car with coolant, including the resevoir, but still no heat.  1. Can the operation of the system without proper coolant level cause a lingering lack of heat even after the coolant level is restored?  2. Is there a "reset" option available to restore the heater function once the coolant is replenished?  3. Can you offer any guidance on troubleshoot and/or repairing this in general?  Seems quite coincidental that the heater stopped working and the coolant level was down substantially.  Thank you for your help in advance.

Answer
Hello,

For years coolant systems in vehicles have been a closed system. If you are down on coolant, heating problems will occur. I would be very concerned as to engine damage because Northstars do not react well over heating. I would be concerned as to where 3 quarts of coolant went--very concerned!!

I would suggest figuring out where the coolant has gone. To do this, go to a service center that has a pressure tester. I have one in my garage. The radiator is filled to the top and the pressure tester is pumped to 15 pounds. Then wait to see where the coolant is leaking from. These northstars are known for leaking intake manifolds and bad head gaskets.

You need to find the leak first. As far as the heat, its very possible that you may have a air bubble or a bad heater control valve in the engine.

Get the engine looked at first!

Rob

Cadillac Repair

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Rob Painter

Expertise

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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