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Jerry Newton
Jerry Newton, Chevy Technician
Category: Chevy
Satisfied Customers: 4508
Experience:  ASE Master Technician, L1, Master GM Technician. Over 20 years of bumper to bumper GM experience.
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Chevrolet Trailblazer LTZ: my 2002 LTZ Trailblazer has

Customer Question

Hello my 2002 LTZ Trailblazer has an A/C problem the A/C will work when you start it up in the morning an after you drive down the road it stops blowing cool air Ihave swapped out the inside A/c module with one off of my mom,s LTZ an still has the same problem then noticed the outside temp read 50 degrees changed it out an back to correct out side temp but no help on cooling So I checked to see if the clutch on the compressor was dropping out an it was an once it kicks out I can not get it to kick back in Oh when I changed the modules I looked at the clutch on the compressor an it was kicked too. I then checked status wire coming from thecontrol module to the compressor it self with a volt meter an no voltage also checked the other wire coming from relay 44's contact an it read voltage I changed out the module out earlier with my mom's an still not working Have any idea's Thanks Rick
Submitted: 2 years ago.
Category: Chevy
Expert:  Jerry Newton replied 2 years ago.
The engine computer is what controls the AC compressor. The HVAC module sends a request for AC, and the engine computer decides whether to engage the clutch or not. It sounds like the computer has the ability to engage the clutch, since it works at least sometimes. The way to diagnose this is to wait until it acts up, then disconnect the connector at the compressor and test for power and ground on those two wires. If you have power and ground (using a test light across those two terminals is a very quick way to determine this), then the clutch coil itself is no good and the compressor needs to be replaced. If you have no power at that connector when this occurs, then you'll have to work your way back upstream, to the AC compressor relay, and perhaps may require a scan tool to determine why the engine computer isn't engaging the clutch when this occurs. However, I suspect that you have a faulty compressor, that's why I mentioned that first, and I'd start my testing there.