I have a 98 chevy blazer the ac stopped working and the heater stopped working and in the dash there is a clicking sound so i took out the ac fuse in the fuse compartment by the driver side door and it stopped. What could cause the noise and why is it not switching over to heat or ac i'm about to move to colorado? Pleessseee help on another note the 4x4 is not working it got stuck in 4w lo and i took off the shift motor and replaced it along with the tccm and still nothing i manually switched it over to 2w again but every time i hit the switch the light just blinks and the light goes right back to 2w i'm lost.

 

Please tell us everything that does and does not work in your heater system. Does blower work?
Can you change vents. Did the compressor clutch engage?

I THINK your blend door actuator broke.. common failure and causes 'clicking' but why guess at it!

Is there ANYTHING else in your truck that doesnt seem to work quite right? Even if you dont think it's related, it could be important.