2003 Chevrolet Trailblazer • 126,000 miles

2003 trailblazer LTZ with electronic ac/ heat controls, I have the truck 2 years everything worked about 2 weeks ago I had the heat on everything was fine when I shut the car off the heat kept on blowing, finally I removed the fuse to shut it off, however the off button did not work either.
The next day I turned the heat on again no problem, everything works defroster, floor, front vents, when I hit the off button it stayed on.
I got a used one installed it, same problem, did not shut off heat this one also had a few lights out and the outside temp kept going from 50 degrees to 26 that was the temperature and 5 minutes later back up to 50, so IM confused, I know the second one there is a problem with.
but is there anything else I can check before I go to Chevy and get a new one.
Thank You
November 27, 2012.

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