Expert: Van - 12/16/2005

Question
My 2000 Chevy Blazer has been giving me no problems for 3 years now, but the heating system is starting to act up.  The blower works fine and the heat is intermittent.  It will blow hot air for a while, then blow luke warm, and then back forth for the rest of the time I spend in the car.  Could this be the diverter box within the dash?  I have changed the thermostat and the fluid level looks good, and the engine temperature is running normal - what could be causing the system to work whenever it wants? - its December and cold...I need a fix!  Thanks

Answer
Hello Roman,
I don't know what a diverter box is, but fluid level would have been my first suggestion, meaning inside the engine, not the recovery tank. But if you replaced the thermostat due to this problem, I assume you were very careful to make sure all the air was purged, and it is full.
There is a door in the heater/ac housing that directs the airflow either through, or around the heater core, and I would bet that is what is happening. However, that door is controlled by the control module, according to the selected, or desired heat.
I honestly don't know where that module gets its feedback as far as the delivered temperature is concerned. The little electric motor that operates the door has a feedback potentiometer inside it, but to the best of my knowledge, it is just a position sensor, and has nothing to do with temperature.
So I would think it is something in the module itself.

Here is a link to a GM forum I frequent, and if you would go there, and sign up, you can get some answers that I don't have. It is totally free, and a great site.

http://www.chevytalk.org/

Van