2005 GMC Sierra 1500 - heater blows, but only cold air
2005 GMC Sierra 1500 4.8l 55k miles. Blower works in all heat settings, just no hot/warm air. Driver and passenger sides are the same. Feel little to no difference when moving the temp sliders from cold to hot. Is this a fuse/relay problem?
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Re: 2005 GMC Sierra 1500 - heater blows, but only cold...
Check coolant level. Check for heat at the heater hose going from water pump to heater core at firewall. Check to see that cable is moving coolant control valve from the closed to open position. Low mileage so it shouldn't be plugged heater core.
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I had this happen on my 2004 also. I have the climate zone control module that allows for adjustment for driver or passenger temps. I had to cycle between hot and cold on the passenger side and switch it between defrost and feet, then power off everything for a long period of time using the power button on the control, this finally got the solenoid to become unstuck. If that doesn't work then you have to get into the heater/air ducts under passenger side, which is difficult, to manually unstick or replace the locked solenoid.
Probably passenger temp actuator. Make sure connectors are fully seated on right I/P junction block. If they are, it's more than likely a faulty actuator. Dash pad and air distribution ductwork have to be removed to access actuator.