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Q: i have a 2005 gmc c5500 the heater motor comes on for 20 sec when first start truck then nothing

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i have a 2005 c5500 heater motor comes on for 20 sec when i first start truck then nothing
My car has an automatic transmission.

Hello - I suspect this may be a problem with the fan motor resistor pack. If the fan control is put in the "Max" or "High" speed position, does the fan continue to run? Does the fan only run for 20 seconds, then stop in the Low and/or Med fan speed positions? If the answer is "Yes" to these 2 questions, the heater fan resistor pack is bad, and needs to be replaced. I would recommend having a Heater Is Not Working Inspection completed by a mobile, professional mechanic, such as one from YourMechanic, to diagnose this problem, get an accurate assessment of the damage and provide an estimate for repairs.

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