I have a 2005 GMC C5500 when I first start my truck the heater fan will come on for about 20 sec and then nothing I replaced the resistor and checked heater motor all ok.
Hello. The fan speed control module (different from the resistor pack) is the common source for this behavior. The Part # is 89018778. If you need to have this done, a certified technician from YourMechanic can come to your location to conduct this repair or can conduct a diagnosis of the heater problem first.
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