1998 Blazer with the auto climate controls: I have replaced the ambient cabin air temperature sensor that is in the headliner by your left ear, both floor and vent air output sensors, and the sun-load sensor on top of the dash. A/C worked great all summer, kept it on auto and the temp **** 70-72. Now that it is getting cold out it seems I have to turn the dial up to 78 or more for it to activate the heat, and then it doesn't blow hard for long so I have to usually bump it another notch to keep it blowing. Its in the 40s - 50s right now, so it should be plenty cold to kick the heat into high speed. Any suggestions ?