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Discussion Starter · #1 ·
Yesterday the AC quit working. Set to 65 degrees and it only blows hot air.

The AC compressor clutch is not turning on. Fuse 35 for AC Clutch is good. Swapped relay 67 and still doesn't fire the clutch.

The climate control system appears to be displaying all correctly.

I searched the forums and find no AC L5P discussions. I'll be checking voltage going to the clutch and maybe that will narrow things down before a trip to the dealer on Monday. Just had it in two weeks ago for a Fuel Pump Control module failure.

Any input would be appreciated.

Jim
 

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Yesterday the AC quit working. Set to 65 degrees and it only blows hot air.

The AC compressor clutch is not turning on. Fuse 35 for AC Clutch is good. Swapped relay 67 and still doesn't fire the clutch.

The climate control system appears to be displaying all correctly.

I searched the forums and find no AC L5P discussions. I'll be checking voltage going to the clutch and maybe that will narrow things down before a trip to the dealer on Monday. Just had it in two weeks ago for a Fuel Pump Control module failure.

Any input would be appreciated.

Jim
Please know that the engine package isn’t going to really help with an ac diagnosis. Year of the truck and type of ac system (auto or manual) are needed. Also, it is very important to know if the ecm is running a factory or aftermarket tune.

If the fuse and the relay are “good”, you still don’t know if you have all of the necessary power supplies to the relay or fuse. If those are present, you’ll need scan tool data out of the hvac controller and ecm to know why the ecm isn’t firing off the compressor clutch relay.
 

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Discussion Starter · #3 ·
Please know that the engine package isn’t going to really help with an ac diagnosis. Year of the truck and type of ac system (auto or manual) are needed. Also, it is very important to know if the ecm is running a factory or aftermarket tune.

If the fuse and the relay are “good”, you still don’t know if you have all of the necessary power supplies to the relay or fuse. If those are present, you’ll need scan tool data out of the hvac controller and ecm to know why the ecm isn’t firing off the compressor clutch relay.
Please know that the engine package isn’t going to really help with an ac diagnosis. Year of the truck and type of ac system (auto or manual) are needed. Also, it is very important to know if the ecm is running a factory or aftermarket tune.

If the fuse and the relay are “good”, you still don’t know if you have all of the necessary power supplies to the relay or fuse. If those are present, you’ll need scan tool data out of the hvac controller and ecm to know why the ecm isn’t firing off the compressor clutch relay.
2018 3500 diesel, automatic ac, no tune.
 

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Discussion Starter · #5 ·
Well, the service department looked at my truck and determined it was low on Freon. Said it had none. Evidently a hose rubbed through and it all leaked out. Must have been a pretty abrupt leak to be operating fine in the morning and gone in the afternoon.

Does anyone know if the refrigerant pressure is available on the OBD port? .

I've asked for photos and also the old hose. I will contact Chevy to get an answer to how their design would have allowed that to happen and hopefully be able to provide info to the forum to save others from the same experience. I'll post photos.
 

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Discussion Starter · #6 ·
You may want to be proactive and make sure your AC hose is not going to contact the sharp edge of the air filter apparatus.


The first photo shows the hose that had been worn through causing the refrigerant to leak out.



20210722_142947.jpg


This is the sharp edge that wore the hole through the braiding then the hose

20210722_143050.jpg


You can see the braiding did not save the hose

20210722_143001.jpg


The whole assembly needed to be replaced

20210722_142928.jpg

Now there is clearance, but something needs to be added to keep the hose from going back towards the sharp edge

20210722_143024.jpg


It was not a cheap trip to the dealer.

Jim
 

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Jim, Thanks for the advice. Going to check my clearance now. Sorry you had to be the sacrififical lamb!

Sent from my SM-G975U1 using Tapatalk
 

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Discussion Starter · #8 ·
Jim, Thanks for the advice. Going to check my clearance now. Sorry you had to be the sacrififical lamb!

Sent from my SM-G975U1 using Tapatalk
Also may want to check on the other side of the cannister. Looks like it can abrade a wire bundle. Already started on mine.

Jim
 
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