I'm having some problems with my A/C and HVAC on my "new" (recently purchased with 162k miles) '03 Silverado. First off, my compressor is making a "whooshing" noise so Im pretty sure it or the clutches are going bad (although it doesn't seem to have any trouble engaging). The big issue now though is that when I first start the truck up, no matter what vents I have set to blow, the ones on the top of the dash under the winshield are the only ones that blow. Then, the main vents I selected come on for about 20 seconds while a "clicking" sound in the dash taps on simultaneously for the 20 seconds. Once the tapping stops, the air goes back to coming out of the top of the top of the dash again. The "recycle air" button also deactivates itself as well. There was an occasional tapping at first start before every now and then for only a few seconds, but it never actually seemed to effect anything. These new issues all started yesterday when I had to unplug the batter to install my new MIT. Do I need a new HVAC unit (mine is the one with dual climate control), or is it something inside the dash. Is this a common issue with higher mileage GM trucks.

 

I'm not a member of this other forum yet, but these guys were having the EXACT same issue as me. This has to be a fairly common issue among these trucks when the battery is unplugged for a period of time.

HVAC Module - Page 2 - Chevrolet Forum - Chevy Enthusiasts Forums

 

Replace the mode door actuator and perform a actuator relearn and you will be fixed common problem. Then take the truck to a dealer and have them reprogram the HVAC control head with the latest calibrations. 03-05's had a ton of calibration updates to solve all kinds of little gremlins that develop at weird times.

IF you lay down on the drivers side floor board and look at the HVAC case it's the actuator that's dead square in the middle of the case on the side of it just above and forward of the gas pedal.

Battery disconnect has no bearing on HVAC working correctly.

 

I went to a "Pull-A-Part" place toady and looked at several 03+ GM trucks, and ALL of them already had the actuator robbed off. I did notice another actuator under the very center of the dash that looked IDENTICAL to the one I needed (except it didn't use the gear arm like the main one does. I took it out and the gear arm fit fight into it and the part number was very close (it was P/N: 52402599 vs my 52402598). The guy at the counter didn't even charge me for it so it only cost me $2 to get in, 20 min. worth of gas, and my time. I got home and installed it and it seems to work just fine and fixed the problem. I'll keep you posted if it burns up for some reason due to different voltage or something, but everything on it looked identical: markings, plugs, mounts, gear, and all. It did say "R" on the big letter on the label where the original one said "DZ", but I don't think that really matters. Probably just GM charging for different parts that are really the same. Just a tip for anyone else who may need one of these and can't seem to find one, but doesn't want to sped $50 on a new one.