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Gary, ASE Certified Technician
Category: GMC
Satisfied Customers: 16769
Experience:  GCM master tech over 25 years
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GMC: My 04 sierra blows only in defrost and max hot on driver

Customer Question

My 04 sierra blows only in defrost and max hot on driver side and normal on right side, I try to reset disconnecting battery and waiting 3 or 4 minutes then when I put it back together I turn key and everything work find for a second and then go back to defrost and hot on driver. I cycle the key a few times trying to here any actuator stock making noise but it didn't. Now it will not do it any more. Do you think I have a control head problem or I could have multiple actuator bad at the same time? I want to mention also that illumination from one side of cold & hot controls don't work.
Submitted: 2 years ago.
Category: GMC
Expert:  Gary replied 2 years ago.
I am very sorry for the long waitwe have seen both the actuators and the control head and a very few with wiring issues from the control head to the actuators90 % are usually bad actuatorsthe best action to take is to make sure there are NO B codes in the body control module if there are any codes usually correcting those codes will usually correct this issueif NO codes in the body control module then a scan tool needs to be plugged into the truck and make sure the most current programming in installed into the heater controller and see if they can control the actuators with the scan tool if it will not they need to test for the signals to both actuators and be sure the actuators are being told to operateif that is updated and it still does this then the odds are the 2 actuators for the drivers side temp and mode need to be replaced