2002 GMC Envoy AC problems and what Ive tried to fix them

[JonLock88]

Hello all! I'm completely new to the forum, but I have searched google trying to pin down the problem I'm having and no luck so far....atleast not the kind I want. My gut tells me that I have a bad Ac compressor coil (clutch won't engage). But, I'm hoping that some how by some chance that I'm missing something and that the Ac gurus here will easily see my mistakes and I kindly point them out to me.

So, to the issue. My Ac won't work! I turned the knob and pressed the buttons and it just blows warm air. That's all that is possible to try right?

Just kidding! I haven't done much more than that, but I'll go over what I have done most recently.

I used a multimeter to test the DC volts to all of the connections I know about. With the envoy running and Ac set to auto and temp turned all the way down (this vehicle doesn't have a "AC ON" position so that's the most I can do to turn the Ac on. I tested the sensors and wrote down the measurements, so I'm just going to list the sensor and then the data on each one. So, what I believe is the *low pressure sensor: pin A - 4.75vdc Pin B - 0.00vdc.* *AC RELAY: pin 85 - 13.77vdc Pin 87 - 13.92vdc Pin 30 - 0.00vdc Pin 86 - 0.00vdc*. *3 pin connector on side of compressor (MEASURING FEMALE END THAT COMES OFF HARNESS AND PLUGS INTO CONNECTOR ON COMPRESSOR) Pin A - 0.23vdc Pin B and C get 0.02 and 0.03 volts DC.*

That's all that I've tested, all that I know how to test with a multimeter anyway. So, next I made a alligator clips soldered onto a solid core copper wire, with about 1 inch of insulation stripped off the other end and that end ground down to a thin piece about the size of a relay pin under the hood. I started the vehicle, and with the Ac on and engine running and doors open with temp set all the way down fan all the way up, I hooked the alligator clip onto the positive side of the battery and then plugged the now hot wire into (I think?!?!) Pin 30 in the relay/fuse box. The clutch moved slightly in and stayed (but never engaged and actually spun) and when I pulled the wire the clutch released again. I did this 2-3 more times to confirm what it was doing.

My next test is going to be to do exactly as I did above. But with power to it and the vehicle running I'm going to go through the gap in the wheel well and then tap that clutch inward to see if that will make it grab and start to spin. Only thing is, I also used a screw driver to depress the low Pressure side freon port to see if it had any pressure, which it didn't do anything but barely "pssst" air (no freon at all that I could tell) out and I mean BARELY. About as loud as someone quietly "psst'ing" with their mouth. So, before the test I have to figure out how to hook up these Ac gauges (the right way) and have some 134a ready to put in. Because can't the compressor burn up if it spins with no freon in it? I don't want that if it's not already burnt up. I'll let you all know how this experiment goes.

Anyway, any advice, help whatever that you can provide would be absolutely amazing. I've posted in another forum and not gotten any helpful suggestions. I'm hoping you guys will be able to help me out.

Thanks in advance!

[JonLock88]

Ok! So, I did the test. Car running, ac on, and temp all the way down with fan on high. I hooked up my low side line, then my high side line and left the charging line off.... Kinda wondered if any freon in the system might just empty itself out of that line when I opened either valve on the Ac gauges but I tried it anyway.

So, I put direct power from the battery to the relay....and I think it's Pin 86 that puts the power to the clutch, not 30 like I said earlier. Anyway, using a wooden paint roller handle I fished it through the driver side wheel well and while holding a flash light to see, I was able to use my other hand to push against the clutch after it attempted to engage. IT WORKED the clutch grabbed and started spinning. But no pressure at all on either gauge....i opened the valve on each one to see if anything would happen and nothing. No pressure, no spewing freon nothing. So, I pulled power from pin 86 and the clutch disengaged and thats when I went and killed the engine and then typed this post. Not 100% sure what this means. But, I'm thinking maybe it means I have a bad compressor coil (it sat for 2 years up until 2 months ago) and that there was a leak in my ac system somewhere and not only do I have a bad compressor coil, but also no freon and a leak. OR, my ac gauges just don't work. I've used them on other ports before (hotel AC'S and the like) and they worked then. But this is the first time I have tried using the gauges with the adapters to connect to a vehicle. So.Im not sure if they are broken or if my system really has no pressure at all.

Hope this helps you guys help me.

Thanks again in advance!

[JonLock88]

Noone can help me out with my issue?

[JohnHere]

I'm new here as well and not a "professional" Mobile AC tech. But I have worked on automotive AC systems on my own for many years, going back to the R12 era. So I'll offer some suggestions.
You've certainly done your due diligence on the electrical side of the system. I wouldn't recommend jumping any sensors, though, as forcing the compressor to run with low refrigerant will starve it for oil, most likely ruin it, and create another major (and expensive) problem.
In the electrical area, one of your results does jump out at me. Your low-pressure sensor reading on Pin B is zero volts, suggesting that the sensor switch isn't closing and that the system has very little or no refrigerant in it. Additionally, you noted no pressure on your manifold gauge set. Assuming your gauges are working and correctly connected to the system, this too would indicate no refrigerant in the system. However, your readings of zero (and no refrigerant coming out of the center port with both hand valves open) could be the result of your gauge-set adapters not depressing the vehicle's Shrader valves. I suggest re-testing with an R134a-specific manifold gauge set with the proper hoses and adapters and see what you get.
Should you still have zero pressure readings, I'd say that all the refrigerant has leaked out. Discounting a potential clutch issue for now, I would pull a deep vacuum on the system first and see whether it holds. If it does, then re-charge the system by weight according to the under-hood decal, adding some dye to the system at the same time. The correct charge should now allow the clutch to engage if it's working right. If not, then you'll need to adjust the clutch air gap or replace the clutch itself if it's bad.
Assuming you can get the system running for a few days, proceed to leak-checking. Typical areas to look for leaks include all the rubber hoses, all the line connections, the condenser, the condensate draining from under the vehicle (indicating a leak in the evaporator), the compressor shaft seal, and the compressor body. Also check to ensure that the vehicle's low-side and high-side service ports have caps on them. Any noticeable corrosion on a metal refrigerant line (particularly the high side) or other metal component should also be suspect.

[JonLock88]

Thank you Sir for the help!

Last night after posting my last post describing what I had tried, I sort of come to the same conclusion that you suggested. Get another pressure gauge to ensure that the other was reading properly. I didn't have another set of manifold gauges. But I did have a large can of 134 with a low pressure side gauge and hose on it. I started the compressor clutch In the same fashion I described in previous post. Then began adding freon to the low pressure side port. Well, I added and added and added (not THAT much. But a few second squeeze on the trigger 5-6 times). I don't know if this is normal or not, but it did catch my eye enough to note here anyway. When I would squeeze the trigger it would show pressure on the gauge and when I would release the trigger it would show 0 still. I did this several times and each time it showed 0 after I released the trigger. So I killed it after like 3-5 minutes of the compressor running while I was adding the freon. Then, after the compressor and engine stopped the gauge shot up to 24-25 pounds (was within the "charged" part of the gauge.) So, I figured I'd take the opportunity to measure it after it sat for a night. Today I measured it and it was down to about 20-22 pounds. So a loss of around 3-5 pounds over night. So. That leads me to believe the gauges are correct and I simply have a leak in my system and it was down to 0 pounds.

Next question then. Is it save to use the cans of freon that include the leak sealer and UV dye in it? I have about 1/2 to 3/4 of the big can left. Plus 1 full can of just 134 and also 1 full can of 134 plus sealer and dye. Money is very tight, so I'm trying to fix this with as little money as I can. But I don't want to do something that will screw my system up a few months down the line. I'm hoping that me adding the freon while the compressor was running prevented any damage to the compressor while it was running.

So what do you think? I don't have a vacuum pump, so I can't do a vacuum test. But I assume the loss of pressure proves the leak?

Thank you!

[JohnHere]

I believe the experts on this board would strongly advise against introducing any type of sealer into your AC system, and I agree. Sealers and other "miracle enhancers" often clog-up components and create additional and costly problems that weren't there before. Cans with the trigger, hose, and gauge are notoriously inaccurate and are also known in the trade as Death Kits...for good reason. I recommend using nothing but pure refrigerant...R134a in your vehicle...and a little UV dye (one ounce or less) for leak checking. That's all.
You can use the little 12-ounce cans of pure refrigerant for re-charging into a well-held vacuum. But a much better option is weighing-in a precise charge using a refrigerant scale.
I understand that AutoZone will lend out an R134a manifold gauge set, a vacuum pump, and a scale. I've never borrowed anything from them, though, because I have all my own tools and equipment.
Bear in mind that Mobile AC repair work isn't DIY friendly and can be hazardous. If you do decide to work on it yourself, be sure to at least wear gloves and safety glasses. Refrigerant mixed with oil and who-knows-what can be very nasty stuff.
If you start to feel a bit overwhelmed by it all, it's probably best to leave it to a pro even though it will cost more.

[Cusser]

I believe the experts on this board would strongly advise against introducing any type of sealer into your AC system, and I agree. Sealers and other "miracle enhancers" often clog-up components and create additional and costly problems that weren't there before. Cans with the trigger, hose, and gauge are notoriously inaccurate and are also known in the trade as Death Kits...for good reason. I recommend using nothing but pure refrigerant...R134a in your vehicle...and a little UV dye (one ounce or less) for leak checking. That's all.

Above true in my opinion. Refrigerant, correct refrigeration oil and (optional) UV dye.

I understand that AutoZone will lend out an R134a manifold gauge set, a vacuum pump, and a scale. I've never borrowed anything from them, though, because I have all my own tools and equipment.

Last summer I was 100 miles away from my vacuum pump and gauge set, so I borrowed those from local Autozone, and they worked great.

be sure to at least wear gloves and safety glasses.
If you start to feel a bit overwhelmed by it all, it's probably best to leave it to a pro even though it will cost more.

This.