GM climate control system fail
If you have a GM climate control system in your vehicle and the blower motor stays on HIGH and won’t shut off even when the car is off and the key out, chances are the blower motor control processor is toast or the HVAC control module is damaged. The processor is what lets you select and infinite range of blower speeds. In vehicles without climate control, you’ve only got three blower speeds and those are controlled by a blower motor relay. Sure, those blow out, but they’re only about $30 to replace.
If your climate controlled blower processor is shot, be prepared to spend mucho bucks for a replacement.
But before you start throwing expensive parts at the problem, you’ll have to do some checking. Start by testing the gray/black wire at the blower motor control processor. First, try grounding the wire. Then try removing it. If the blower stops with either of these steps, the problem is in the HVAC control module. However, if the blower continues to run at high speed with either of those tests, replace the blower motor control processor.
Just as an FYI, the retail price of the blower motor control processor is $280.34. There are a few places online that rebuild these puppies. Search for “HVAC rebuilder.” I know of some reputable PCM rebuilders, but don’t have any experience with HVAC rebuilders. So you’re taking your chances.
