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Jerry Newton
Jerry Newton, Chevy Technician
Category: Chevy
Satisfied Customers: 4829
Experience:  ASE Master Technician, L1, Master GM Technician. Over 20 years of bumper to bumper GM experience.
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Chevrolet HD2500: BUTCH, MY 2006 HD2500 HA THE TYPICAL DRIVERSIDE

Customer Question

HI BUTCH, MY 2006 HD2500 HA THE TYPICAL DRIVERSIDE FAILURE TO HEATING WHEN A/C IS ON. PROBLEM NOW IS I CANNOT GET COMPRESSOR TO COME ON I'VE CHECKED ALL PRESSURE SWITCHES AND COMPRESSOR.OHM'D CLUTCH ON COMPRESSOR AND CHECKED RELAYS. ALL GOOD, COMPRESSOR CAME ON THE OTHERDAY WHEN IT WAS 58dF. OAT.RAN FINE TILL DAY WARMED UP AND WOULD'NT COME BACK ON. I CANNOT CHANGE MY COMFORT CONTROLS FROM FLOOR TO DEFROT AND IF I CHANGE TO ANY SELECTION OTHER THAN DASH VENTS IT GOES STRAIHT TO HEATING. ANY HELP WOULD BE GREAT. I DID GET FAILURE CODES B3770 & B0408
Submitted: 2 years ago.
Category: Chevy
Expert:  Jerry Newton replied 2 years ago.
There is a calibration update for these trucks that should be applied before diagnosing further. This is something only your dealer can do for you. Aside from that, the temperature issue (along with those trouble codes) usually points to a faulty temp door actuator, which is located near the gas pedal on the HVAC case. You should be able to change modes, though, and that doesn't affect the AC operation. You have those trouble codes.... does that mean you have a scan tool that can read HVAC data? You would be able to see actual vs. commanded blend door actuator values, and other good information here. Also would be able to see if AC is being commanded, and query the PCM about it, because ultimately, the PCM controls the compressor, not the HVAC controller. HVAC simply sends a request to PCM to turn on the compressor, the PCM makes the decision, and can disable it due to a variety of issues, all of which can be seen on a good scan tool.
Customer: replied 2 years ago.
Jerry the codes came from me from the local shop that I use for my other vehicles so I trust their diagnosis I've ordered the blend door for the left side down by the gas pedal as well as the one over the transmission pump on the bottom which is the one I know makes the noise of this if its getting hung up I took the battery disconnected it when I brought it back home from the shop let it sit for a couple of minutes put it back up turn the key on for a couple of minutes then off then started the truck and of course the air conditioner worked throws me out of the cab then eventually satisfied or shut off not to come back on but I know there has to be a temperature sensor in there some where that's what I would like to get my hands on to check.I'm going to go by OBD tool any suggestions
Expert:  Jerry Newton replied 2 years ago.
If I had to guess at the compressor issue, I'd say you have a faulty pressure switch under the hood, just based on the number of times I've seen bad switches. I wouldn't replace it based solely on that, but that's my educated guess. There is a temp sensor, but you don't have a trouble code for a temp sensor, and it would have been a B code like the other ones. The AC pressure sensor is an input to the PCM, so the PCM will decide not to engage the compressor based on that, and will likely set a trouble code as well if that's the case. Good diagnosis is key.