AC problem 01 Yukon XL 5.3 w/rear air

[LordWayback]

No worries.

HVAC control modules have been known to fail on these trucks.

If you can verify the relay is actually receiving the trigger signal to begin with and the relay is passing that current down the line to the clutch, that would be good to know. Clutch may be good and relay might be good too. But if they aren't getting the go-ahead from the control side of things, nothing will happen at the clutch.

This is my logic (right or wrong) test the critical things that can be tested easily and cheaply first...
Is the HVAC control sending the command to activate in the first place?
Is the command (correct voltage) making it all the way through the wiring harness, to the relay, triggering the relay and out the other side, and on to the end of the line (clutch)?

Where am I looking for this control module? Are you referring to this?

 

[rockola1971]

Where am I looking for this control module? Are you referring to this?

Since clutch fell apart just unplug the wiring harnes from it. Start engine and turn a/c on max. Measure for 12V+ at clutch wiring harness, it should be there if pressure is ok and everything else is working. If not then you need to check pressures on low/high side.

 

[LordWayback]

I’ll test this in a bit I just tried the ac and there’s now no air blowing from the front the rear air blows air just not cold I’m currently on the path for that issue because it’ll stop voltage from being sent In the first place

Since clutch fell apart just unplug the wiring harnes from it. Start engine and turn a/c on max. Measure for 12V+ at clutch wiring harness, it should be there if pressure is ok and everything else is working. If not then you need to check pressures on low/high side.

 

[Merc1973]

If you have ruled out low refrigerant and a bad low pressure switch, The most common issue for the clutch would be an increased Air Gap. As the.clutch wears thinner, it will require more voltage/amps to electromagnetically pull the clutch across the larger air gap.

Some.auto manufacturers have AC compressor clutch that can be taken apart to add shims to reduce air gap as they age. Thats what happened to my original compressor at 285k miles. I just bought a new Denso instead of playing with that worn out thing.

 

[Scottydoggs]

Where am I looking for this control module? Are you referring to this?

up a bit and to the left of the actuator hes taking off.

 

[LordWayback]

I’ll test this in a bit I just tried the ac and there’s now no air blowing from the front the rear air blows air just not cold I’m currently on the path for that issue because it’ll stop voltage from being sent In the first place.

Since clutch fell apart just unplug the wiring harnes from it. Start engine and turn a/c on max. Measure for 12V+ at clutch wiring harness, it should be there if pressure is ok and everything else is working. If not then you need to check pressures on low/high side.

up a bit and to the left of the actuator hes taking off.

I’ll mess with that bit when I get back from grabbing food I confirmed the blower motor works perfectly fine even from a 01 manufacturing date

 

[LordWayback]

If you have ruled out low refrigerant and a bad low pressure switch, The most common issue for the clutch would be an increased Air Gap. As the.clutch wears thinner, it will require more voltage/amps to electromagnetically pull the clutch across the larger air gap.

Some.auto manufacturers have AC compressor clutch that can be taken apart to add shims to reduce air gap as they age. Thats what happened to my original compressor at 285k miles. I just bought a new Denso instead of playing with that worn out thing.

My compressor clutch is making a nasty noise when I try and turn it on so it’s probably that I’ll try the new one when it comes in it sounds like it’s activating just gotta mess with the blender and new China clutch

 

[rockola1971]

I’ll test this in a bit I just tried the ac and there’s now no air blowing from the front the rear air blows air just not cold I’m currently on the path for that issue because it’ll stop voltage from being sent In the first place

2 different issues and 2 different control problems that likely are NOT related. You can have Compressor Clutch working and Blower Fan(s) not working AND vice versa. Looking at the schematic for your vehicle you will see that once that ac relay is closed then all you need is 12v from that 10a fuse (fuse must be good in other words) and that low pressure cutoff switch in the low side refrigerant line must be closed (pressure needs to be roughly 30PSI+ roughly in other words). The low pressure cutoff switch is in series with the PCM which gives the A/C Clutch a ground for its coil which comes from pin C2-55 of the PCM.
Of course your clutch could be fried from a locked up compressor too or just normal wear and tear.
But you did say in your previous post to this one that your clutch "is making a nasty noise when I try and turn it on" so that leads me to believe that you are turning a/c on with engine running and the clutch is engaging or atleast is trying to anyway. If that is the case then look down at the clutch while engine is on and look at center of clutch and see if it is turning at a decent rpm. If it aint then it is slipping because of the air gap issue or compressor is locked up.

 

[LordWayback]

2 different issues and 2 different control problems that likely are NOT related. You can have Compressor Clutch working and Blower Fan(s) not working AND vice versa. Looking at the schematic for your vehicle you will see that once that ac relay is closed then all you need is 12v from that 10a fuse (fuse must be good in other words) and that low pressure cutoff switch in the low side refrigerant line must be closed (pressure needs to be roughly 30PSI+ roughly in other words). The low pressure cutoff switch is in series with the PCM which gives the A/C Clutch a ground for its coil which comes from pin C2-55 of the PCM.
Of course your clutch could be fried from a locked up compressor too or just normal wear and tear.
But you did say in your previous post to this one that your clutch "is making a nasty noise when I try and turn it on" so that leads me to believe that you are turning a/c on with engine running and the clutch is engaging or atleast is trying to anyway. If that is the case then look down at the clutch while engine is on and look at center of clutch and see if it is turning at a decent rpm. If it aint then it is slipping because of the air gap issue or compressor is locked up.

It wasn’t making this noise until today so maybe it’s just my luck waiting on parts can’t fix a slipping clutch with shims I don’t have

 

[rockola1971]

It wasn’t making this noise until today so maybe it’s just my luck waiting on parts can’t fix a slipping clutch with shims I don’t have

You likely would NOT need shims with a new clutch. Id be more worried about the possibility of compressor being locked up causing the clutch to slip.