Ferocity02

iTrader: (59)

Coming home from work today I noticed something strange about my HVAC unit that's never happened before. Both the recirculate and non-recirculate buttons were lit up like they were both on (orange lights). I could physically hear that the HVAC was recirculating, but the AC compressor was not cycling on and off like it usually does when recirculate is on. I had fan speed control, but was not able to control temperature or which vent the air would come out of. The AC button also did not work. Other than the recirculate being on, I think the settings were fixed from when I parked this morning.

Then when I got home, I shut her down, waited a few seconds, and started it back up and it worked like normal again

The only coincidence was that this morning was probably the coldest it's been all winter, so I had the heater on for longer and higher than normal, but turned down the speed and temp before I parked at work.

Anyone else have this issue? Is this a sign that the unit is going bad? It's an '01 Silverado 5.3L with 110K on the clock. HVAC unit is stock, haven't messed with it at all other than maybe moving it a little when I installed a stereo a few months ago.

speedie mc pete

One word to your post... YES. I'm told its the vaccum control door on the heater unit sticking or getting stuck. I've got the same issues but mine is an 03 with a bit more on the clock. Mine also makes a buzzing sound ONLY when cold like being left in the parking lot at work or outside for more than a few hours. Once the buzzing goes away, a few minutes of idling and the truck starts to warm up does all you mentioned above go away with the buzzing. Once the truck has warmed up the above mentioned issues and the buzzing go away. It's like its not happy being left out in the cold.

Ferocity02

iTrader: (59)

Interesting. Even when fully warmed up it still wasn't working until I restarted it. Does it need to be restarted before working again?

Is this a simple fix?

Suburbazine

The control unit (the **** and buttons) is most likely going bad. Relatively cheap fix.

There aren't any vacuum-operated doors on the 00-up trucks...all electronic servos.

Ferocity02

iTrader: (59)

This morning it did not have the issue. I wonder if it will happen again on the way home after work.

Another issue (maybe) that my HVAC has had is that cold air will only come out when the temp **** is set to fully cold. Just turning the temp **** a few clicks towards hot will yield full hot air. There are maybe 2-3 clicks where the temp will be between full cold and fully hot.

Now, when I turn the temp **** from hot to cold I can hear something going on under the dash, I assume is the blend door closing/opening. If it turn the temp **** from one click off full cold to full cold then the door makes a loud noise like its shutting completely. In the rest of the temp range the door is fairly quiet like it might not even be moving.

Could this be further evidence that the servo for the blend door is bad? Anyway to see/test it?

letsrun97z

iTrader: (7)

Weird! I have the same problem mine will do that when I go from low beam to high then click back. I have hid's in both low and high. If you turn the truck off and right back on its back to normal. Have no idea how that switch has anything to do with the hvac.

53bowtie

iTrader: (6)

My truck does this exact same thing. It is not the blend door motor, so I have found out, it is the actual blend door/duct-work that is binding. The only way to pull the duct work apart to see about fixing it is to pull the dash, and even then I dont think you can get parts seperate for it unless you go salvage. Needless to say I just live with it for now. I will wait for the heater core or evaporator to go before I pull the dash.