Rick's Free Auto Repair Advice

My AC stops cooling and the heat comes on

Why does my AC stop cooling

Heater comes on – GM

GM has issued a technical service bulletin (TSB) #04-01-38-008 to address AC stops cooling – heater comes on problems with the HVAC system on the following vehicles:

2003-2005 Cadillac Escalade, Escalade ESV, Escalade EXT
2003-2005 Chevrolet Avalanche, Silverado, Suburban, Tahoe
2003-2005 GMC Sierra, Yukon, Yukon XL

If it seems that the heating/cooling system in your vehicle has a mind of its own, it’s probably because the wiring harness has rubbed through and is touching metal parts. GM says the actuator harness (actuators are the motors that move the mode and temperature doors) may come in contact with a sharp edge on the instrument panel support brace. Once that happens, it will move and touch the metal, causing the actuators to open and close on their own. And it doesn’t have to be just a change in air temperature. The shorting condition can also change air direction modes, moving air from defrost to vent, etc. If you scan the system, you may see the following trouble codes:

B0229 Recirculation Actuator
B0414 Left Air Temperature Actuator
B0424 Right Air Temperature Actuator
B3770 Mode Actuator

You’ll find the problem area on the left side of the opening in the instrument panel. Inspect it for contact with the support brace and repair any damage you find. Then install a protective cover over the harness and friction tape over the sharp edge of the brace

© 2012 Rick Muscoplat

Posted on by Rick Muscoplat

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