Auto Air Conditioning & Heater Repair: Silverado Heater Problem, chevy silverado, 2007 chevy silverado

Question
I have a 2007 Chevy Silverado PU.  The heater blows cold air through all temperatures except 90 degrees (maximum setting).

When I set 90 degrees, the heater blows very hot air.  As soon as I set a lower temperature, the air cools.

How do I repair this problem.

Answer
Hi Mark

I had one of these before unfortunately we replaced all 4 temperature sensors that the scanner told us but the stem continued the same way.  Give me a few days I will try and find out what finally happened. The customer was going to try with dealer a second time.