2000 Blazer alternately blowing hot (3 sec), cold (12 sec), with creeking noise during transititions

Auto facts: 2000 Blazer
Mileage: 196,000 Engine: V6, 4.3L Transmission: Automatic Drivetrain: 4WD, Single climate control
Recently had my AC compressor assembly replaced, renewed accumulator/receiver drier, orifice tube, recharge, etc. The AC was cooling well below par after the repairs. Then is started alternately blowing hot (12 sec), cool (3 sec), etc. with a “spooky” creeking noise coming from within the middle dash during each transitition (blend door?). The mechanic charged the system again and agrees there is a refirgerant leak “somewhere” to account for the marginal cooling capability but the dye put into the system before the repair is not showing up anywhere that he can see (so far, having it checked again today). So, are these 2 separate issues? What are the steps of diagnosis and repair possiblities? I’m getting the the tipping point of car value vs repair but love the ammenities of my “loaded” LT BZR. Any information is appreciated. Thanks!

One problem is with the temperature blend door. This device is buried in the ventilation system behind the dashboard and controls the temperature of the air. When the door is all the way to one side, 100% of the air in your ventilation system comes from the outside or the A/C, when the door is all the way to the other side, 100% of the air comes over the heater core. In-between temperatures are created by in-between blend door positions. The noise you hear is the door swinging from one side to the other. If the A/C is not cold enough, it could be that the door is never fully closing properly so that warm outside air is always mixed with the cold air. So you may only have one problem, not two.

The blend door motor is either controlled by engine vacuum pressure or it is a small electric motor controlled by the electronic climate control system. I’m not sure in your car.

You could have a variety of problems. An electrical short circuit in the motor or somewhere else in the circuit, or a bad climate control computer, or something else. You need a mechanic who can diagnose the whole problem, not just shove more freon into your compressor. (Make sure you explain the whole problem, of course.)

If you put the climate system on “heat” or if you turn off the A/C and set it to vent outside air, does the temperature still swing with the noise? Or does it only happen when the A/C is running? That might help to pinpoint the location of the fault.

Another possibility is that the shop may have dislodged some of the ductwork or loosened an electrical connection while they were working on the system.