So I have an 01 Monte Carlo that is blowing luke-warmish air out the driver side and ice cold air out the passenger side with the AC on. Everything I find online states to replace the heater door actuator on the driver side to fix the issue because one of the two has likely gone bad. Here's where things get tricky now. My car DOES NOT have dual zone climate controls. I even physically checked and there is no actuator on the passenger side. Both sides are controlled by the one on the driver side. If this was an actuator issue, I would assume both sides would be malfunctioning since they're both controlled by the same actuator. Has anyone ever heard of this happening? Am I looking at a potential bad blend door here?

 

Interesting. I am barely familiar with the dual climate system. My 2004 had that same symptom (but I have dual climate control). I found mine a bit by accident. I was changing the evaporator core, which meant removing the entire HVAC module. I found the hinge set up for the blend door appeared a bit tight, Just a little light sanding, nothing crazy so it wasn't so stiff.
But if you don't have the two actuators, I don't see how what I did would work. And I never tore apart a single zone set up.

I am curious what you find when you resolve this. Please keep us updated.

 

So, it appears the issue is not with the blend door. For whatever reason, it's the air conditioner itself that isn't working on the driver side. When driving late last night when it was cool with the AC off, both sides were the exact same temperature. Turn on the AC and the passenger side sharply drops in temperature while the driver side barely changes at all. So it now seems we have exchanged one mystery for another. Why the heck would the AC not work on one side of the car? Will be checking pressures soon. I know the high side valve leaks significantly if you take the plastic cover off, but my solution for that has been to just not take the cover off. Been like that for years now and I've never needed to charge the system.

 

I'm certainly no AC expert, but if one side is blowing cold, then the AC system itself should be fine. There's only one evaporator in the car, and if its getting cold, then the engine bay side of the AC circuit is doing its job. Something is happening after the evaporator thats causing the cold air not to make it down the tube as you want it to.

You'll have to track back through the piping between the vent and the evaporator core to figure out what is different from one side to the other. Does the vent pressure seem the same between the two sides (IE did the tube feeding one side half fall off its mating tube from the evaporator core).

Id probably start by finding a service diagram of the system so you can see exactly how its laid out. Then Id shove one of those cheap USB endoscope cameras into the vent on each side to see what is differnet between the two (attempting to diagnose the issue without tearing the whole dash apart).

 

Pressure is the same on both sides. Unfortunately I could not feed an endoscope camera through because the camera couldn't negotiate the first sharp 90 degree turn inside the system. What I did find however was that the refrigerant was low, down to about 20-25 psi on the low side. I bumped it up to about 35psi which significantly improved the cooling. There is still a difference in temperature between the two sides, but the driver side does eventually get cold now, although it will take a few minutes. The delay in cooling has me suspecting it's the AC clutch causing my issue. It's been showing evidence of bearing failure for a while now, but I didn't originally suspect that as a contributer for only half the car having cold air, especially since it stops making racket when I turn on the AC.

 

I am with bumping on the topic the AC system works. I had my entire dash tore apart (and mine is dual climate), it is one evaporator core. SO if dual climate runs one core, then so does single climate. Makes me wonder what all of different in dual climate vs single climate AC. As I mentioned, on my dual climate 2004 Monte, I accidentally found a blend door issue. I wonder if GM still used a dual blend door on the single climate Montes, but something is preventing it from working as it should. Just a very weird problem.