So when I bought the Tahoe from auction they claimed that the AC was working.
When I went to pick it up they told me when they fired it up after about a year of unuse it wasn’t blowing cold so they recharged it.
Seemed to be OK when I first got it, not ice cold, but pretty good.
Rear fan wasn’t blowing but that fuse was popped and replacing it seems to have gotten that all back in order.
Over the last few weeks of driving it the driver and passenger AC has gotten gradually warmer to the point now where it doesn’t seem to be cool at all. I would think that this just means the leak is bigger than I’d hope but the weird thing is that the rear AC vents are still blowing as cold as they were since I replaced the fuse and got it blowing.
Does this sound like a blend door issue? I crossed my fingers and tried the car off-pull HVAC fuse for 10 seconds-car on- don’t touch anything for 40 seconds relearn but it had no affect. When I adjust each of the driver’s and passenger’s heat/cool slider it goes from really hot to meh cool and I don’t hear any clicking or anything from the footwell/under dash area.
Still nice to have the rear AC vent turned around and pointing down my neck when I drive!
If the rear A/C is still pumping out a ton, but the front is not, that sounds more like evaporator problem. If the rear A/C is ice cold but front is not that could be a restriction, or fluid issue! If refrigerant is getting through the front evaporator properly, both should be cold/sweating under load. A cold inlet with a substantially warmer outlet can point toward poor evaporator feed aka restriction!
You can try the relearn, it won’t hurt anything. Yes pull the HVAC/ECAS Fuse, I had similar issue on my 02 8.1L after I got it running a few years ago. My complaint was AUTO mode sometimes worked, sometimes did not. I did disconnect the battery for 30+ minutes as well for a bit to try to see if that fixed it but it did not. I ended up replacing the cabin air temp sensor (just above your head when driving) and did this relearn on the '02:
Key OFF
Pull HVAC/IGN fuse (or HVAC B fuse)
– Driver-side dash fuse panel. Mine was labelled HVAC 1 and HTR A/C on a 99-02. Yours is 03-06, looks like it is labelled HVAC/ECAS. Either way, pull it and continue on below.
Wait 5 minutes
Reinstall fuses
Key ON (engine OFF)
– Do not touch HVAC controls
Wait 60–90 seconds
– You may hear blend door movement
Mine is just a manual 2 zone front system with hot/cold sliders for driver and passenger so I’m hoping/guessing there isn’t a cabin temp sensor to worry about.
So there’s a second evaporator for the rear ac? I don’t know much about HVAC systems… but I hope I will soon!
Both front sides going warm at the same time doesn’t really fit a blend door: on the manual dual-zone the driver and passenger doors have their own actuators, so both failing together would be a coincidence. And the fact that the sliders still move you from hot to meh-cool means the doors are moving somewhat.
Before pulling anything apart, an infrared thermometer at the vents gives you numbers to compare instead of a feeling. Same setting, fan on high, doors closed, recirc on, engine at steady rpm, then read each front vent and a rear vent one after the other and write them down. If the fronts are clearly warmer than the rear on the same command, Todd’s evaporator/feed direction holds and a door swap won’t fix it. The gradual warming over weeks after a recharge also fits charge loss or a restriction better than a door that failed on a schedule.
And yes, on a Tahoe with rear air there is a second evaporator in the passenger side rear quarter, fed off the same loop.
