So I just recently bought a 2006 Chevy Trailblazer lt from a dealership,who gave a 5 day return policy. Took it to a mechanic who said the HVAC door actuator(I believe driver side) needed to be replaced as we didnt get heat/ac coming from the front vents just the dash and the floor.
So wr took it back to them and they wanted to see what was going on with there techs. Fine whatever. They said that they didnt see a problem with it etc and that the AC was completely empty so they filled it back up etc. Covered the cost so we didnt have to worry anf it worked fine until yesterday. I go out to start it and I hear a loud clicking noise etc so I shut it off and turn it back on no noise AC works fine until yesterday afternoon and it wouldn't blow out the front vents so we messed with some buttons and got it to blow(so maybe our fault we didnt have it blowing out the front vents).

Well I go to start it again today and it makes that same loud clicking noise again and shuts off. So I start to reverse and it comes back on again then after 5 seconds it shuts off. But no air coming from the front vents just the dash and floor again so I mess with some buttons and get it to work coming out of the front vents and the noise is gone.

What could be the issue? My mechanic said the actuator needed to be replaced when I bought it took it to the dealership which said they fixed the AC issue and the vents blowing by just adding some coolant and that worked until now but it seems to me they hould have just fixed the actuator in the first place.

 

Can you describe the clicking? Metal on metal? From where is it coming?

When you say the HVAC was working, could you control from where it blew and also the temperature?

Could the clicking be the sound of a skipping gear from under the dash? The blend door actuator in my 1999 is electronic and the mechanism will fail when a gear cracks and will slip on the axle that engages with the blend door shaft. Everything else in the HVAC system can be working correctly but if the blend-door is broken, then you can get only heat.

I'd be concerned that the AC refrigerant all bled out. Some loss would seem reasonable but all of it seems like there could be a big leak somewhere.

Perhaps someone more experienced than I can point you in the right direction.

 

I am not sure sounds like its coming from the dash and sounds like plastic clicking doesnt sound like its coming from under the hood and now the brake is making a clicking noise when I apply them while I am parked. I have also did it and tpuched the shifter and that is clicking as well as slightly vibrating. There are also 3 door actuators in this vehicle. And for that vehicle to have the whole AC empty because its really used and is old not aure where they got it from besides telling me it was a trade in and they just got it. They did a basic safety check when they received it.

 

On my 07 TBSS had to replace the blend door actuator and about a month after that my climate controls died so had to replace that also. But it was making the same noise you are describing.