[Solved] 2016 Yukon XL AC Clutch Relay, where is it? Service Manual lies...

[Kittmaster]

My turn as finally come for something "major" to me has come for repair. We just finished our camping season, everything went great. Took the wife to a doc appointment, and noticed it was "cool", I quietly put it on LO and then it dawned on me, damn, AC not working.

Finally got the gauges on it, the low side static at 56F is around 22PSI, so it is low charge and on our last trip with the AC working must have just had the min threshold to get us through....so be it.

So, I am one of those who very early on actually bought the entire 7 volume hard copy official GM service manuals set and used them to help figure this out... and of course.... I think they are lying to me....why? Well... the components are all where the manual says they are.... the relay for the compressor, no where to be found....on my 93 vette, to refill the R12, just grab a wire, short the low side switch, fill, have a nice day. This truck has a 3 wire, from 5V from the ECU, what looks like a variable sensor from ground to a fixed voltage divider to measure a window of high to low pressure I'm guessing. So I can't just "jump" it to turn on the compressor to fill it.

The Google tells me the other option is to find the compressor relay and bypass the terminals and direct power with a paper clip... yup, makes sense to me... says it should be located in the under hood fuse box next to fuse 60 10A (valid and found), KR29 (relay in service manual)... no where to be found. No compressor listed on fuse cover, no nothing.

So, after an hour or so of hunting I see some random Omron relay down near the steering column "taped" to a harness... the four wires routed to the relay don't match anything to the service manual.... so NO idea... so I just stopped there.

This is a stupid thing of.... I just need to get the compressor to turn on to fill it... I only have simple scan tools like Bluedriver for basic scanning the ecu and sub modules, I don't have a tech2, which I "assume" can force it on? Does anyone know?

Any idea on where the ac clutch relay might be? .... Or what I should look/do next?

Frustrating to say the least.

Thanks.

Chris

 

[blondie70]

Can't you just hook up the refrigerant, open the valve and let run into the low side....the pressure comes up, the compressor comes on (if you have engine running and AC turned on)...the compressor goes off when it sucks the press. down, then comes back on when pressure comes back up.....etc.....soon, if you are filling it, it will keep running steadily and you can top it off as you wish...............good luck !.......that's how I do it anyway.

 

[Kittmaster]

I always thought the compressor needed to be on to draw it in?

Does the little cans have enough to push into it?

I've never done it that way, but I'm open to try it, I've always jumped the switch to suck it in.

 

[Kittmaster]

Can't you just hook up the refrigerant, open the valve and let run into the low side....the pressure comes up, the compressor comes on (if you have engine running and AC turned on)...the compressor goes off when it sucks the press. down, then comes back on when pressure comes back up.....etc.....soon, if you are filling it, it will keep running steadily and you can top it off as you wish...............good luck !.......that's how I do it anyway.

So I actually had a buy a new R-134a hose to add to the low side, I guess my old one had an issue, this method worked immediately and the compressor came on.

So the outside temp here is around 57F which is not ideal so I spit balled it.

The low side static charge is around 50PSI with the engine off.

With engine running, the low side drops to around 25PSI and the High side is around 140-150PSI and varies a bit.

The compressor is solidly on, no cycling, but with the temps in sync mode, manual, all on "LO" and fans on high, I'm only seeing about 74F coming out of the vent with my IR temp gauge... and that thing is spot on...

I used my scan tool to run the actuator door calibrations. I've followed the service manual procedure to reset the HVAC module.

I had hear and feel the door between hot/cold, so I don't think it is broke or stuck.

Hoping someone may have an idea on what next?

 

[Kittmaster]

I got this solved.....

As an FYI, whoever designed this vehicle needs to have their tools taken away and thrown into prison....forever.

What moron solders the AC clutch relay to a pcb below the fuse box assembly that is inaccessible and non replaceable? So without a scan tool, can't turn it on... so there's that.

I found that my AC hose to the R-134A can was defective and not pushing the tab down in the can so it would never pressurize the hose hence all the BS. Once I bought a new one, it allowed me to get enough pressure to engage the compressor clutch and fill it.

My scan tool was reporting no DTC codes but it still wasn't cooling.

I did a relearn on the actuators and then it flashed "clear dtc codes", re-ran the dtc code checker and it popped up a code.... sure enough "low ac coolant"...as soon as I clear the codes, put the temp on LO, fans on HI, temps dropped to around 43F out of the vents. The low side around 25PSI and high side around 150PSI at 60F.

I'll recheck it, but seems to be ok for now.