Climate Control Not Sdensing Temperature 2003 Lt

[punkieys17]

My 2003 1500LT's auto electronic climate control (auto a/c) is not sensing the sir temperature on either side of the cabin.

 

The symptoms are that it is defaulting to manual mode - so below 90 degrees the system cools continually, at 90 degrees or above it heats. If the system is put on auto then the fan goes full blast and does not slow - no matter what the temperature in the cabin.

 

The vents appear to be responding - certainly the shift between the feet, the air vents and the defrost is happening.

 

I thought it must be the head unit so bought a warranted used replacement - but its exhibiting the same problems.

 

I would be very grateful for any suggestions that may help me diagnose the problem.

 

Julian