heat stuck on.....

the heat on my 02 trailblazer is stuck on in hot or cold position...if you turn a/c on engine idles low then high low then high...any ideas as to the problem?

Welcome to AF, "stuck on in hot or cold", what does that mean?

what i mean is no matter where it is set within the blue to red sections of the heat adjustment it stays hot. no a/c at all, just a low then high idle speed when it is turned on

This can be caused by the dash control or the accompanying temp door actuator, the proper diagnosis will require looking at the temp door actuator to see if it moves with the dial, most likely it will not. A shop manual will be required to pinpoint the problem.