99 Blazer LT Heat/AC Issues
 

Hi All
I'm A new member to the forum,and I've read about all 300+ pages of threads. But this heater thing is driving me crazy. I replaced multifunction switch on column about a week ago and now all of a sudden my heater has gone wacky. (probably has nothing to do w/Multi sw) I can hear and feel the electric actuator switching from heat to AC and never stops.
I Have:
Disconnected battery(to clear computer)
Unplugged HVAC control (to clear)
Cleaned temp sensors (3)
Nothing changes....

Does the electric Actuator motor have switches to tell computer what position it is in? Anything else I can do?

So what comes out of the vents? Hot air then cool air then repeat?
I had a problem something like that and it turned out a gear inside my actuator had a crack in it.

Yes. hot,cold,hot,cold from vents

Definitely sounds like a dying actuator. Remove it and pop the cover off. If the gear is broken, buy a new actuator or try to repair the gear.