I have an SLE model GMC Sierra 2500. I do not have the automatic controlled cabin temperature. I do have the driver/passenger side split selector for the temperature.

Here are my symptoms:

1) Unusual "squeak" noise coming from the dash when the temperature selector(*) is(are) close to the coldest setting;

2) At random times (could hit a bump, or just smooth riding; effectively unpredictable) the driver side will start blowing hot air, while the passenger side maintains temperature at its setting.

Does anyone know what causes this? The most significant problem is the temperature jumping straight to hot. It can be immediately corrected by turning off the truck, and starting it up again, and it is usually fine for some indeterminate amount of time.

If there is an easy cause, is there an easy fix? A relay perhaps?

Any help would be much appreciated!
Thanks!
-Mike Low

Sounds like a driver'* side temp actuator/connection problem........

Hmm.....are there any vacuum hoses in the system? You didn't mention what year your truck is.? Maybe you could try forcing the squeak to occur while the engine is running, leaving the system activated on it'* coldest setting and turn off the engine and listen for the squeaking sound to slowly fade away as the engine vacuum depletes. Could be a bad vacuum hose connection.

His trucks a 03, its all electronic. More than likely its an actuator /or connection issue as mentioned before. My money is on the actuator. Its right above the hump of the floor board, not hard to miss.

How hard is the actuator to get to?

Could the culprit lie with the relays and fuses associated with it?

Seen a lot of actuators go bad. These actuators have a position sensor and motor inside. Majority of the time the sensor goes bad and it loses memory of where its at or needs to go and starts to hunt. The one your needing is locating directly under the radio/hvac controls above the transmission hump on the hvac case. Some vehicles have a shield that needs removed for access.