A few months ago I was checking out my AC system prior to filling it and I accidentally left my pressure switch jumped while testing the aux fan. Low and behold a day or two later the compressor started screaming with no charge in the system and therefore no lubrication when the system called for A/C. I pulled the connector to disable the clutch and the howling stopped. I presume I got to it pretty quickly but the damage was clearly done.

I installed a new receiver/drier and replaced the compressor with a spare unit of unknown origin. I should have flushed the system but did not, mostly because I don't know what that entails. I vacuumed the system for about an hour and a half and it held the vacuum so I took it to a buddy's shop to be filled. It had to go in for state inspection anyway so I figured I'd just have him fill it for me while it was there. Mostly because I knew I'd get the right charge, 25oz out of 12oz cans is a PITA and I know the correct charge is critical so this made the most sense to me. This was mid-June and I don't know what the pressures were at the time but he said "system checked out fine, blowing great". And it was, I distinctly remember July 4th weekend being a scorcher and having a cool truck. Our weather cooled off a bit and the last two weeks rarely got out of the 80s, but I used the A/C every time I drove it and it has functioned great since it was filled. I even called him up one night and thanked him again because of how well it worked.

Sat afternoon the temp was mid-90s with high humidity and the truck had been sitting in the direct sunlight until about 2pm so it was really hot inside. I jumped in and started it up and the A/C sucked. At first I thought the scalding hot dash was making the A/C take a little longer than normal to deliver cold air but after 10 minutes or so I realized that it wasn't making cold air, or so little that it wasn't making a difference since there was only a very minor temp differential. Then I sat in traffic for a half hour and couldn't get any air moving through the condenser beside what the aux fan could provide, and I sat there roasting. After I got moving about a half hour later "cool" air was noticeable but not cold air for sure. I would say the system was operating at about 60% of what it should have been.

Sunday morning the ambient was 77° and sitting in the driveway the air felt chilly cold once again. Later in the day I got in the truck, high 90s now and high humidity and the A/C started off blowing cool air. Not icy cold but it was way improved over the day before despite being hotter outside. Eventually it got better and better and climbed up to about 80% for the next hour and a half, driver's side got cold air for sure but not *really* cold air and it still struggled to keep the cabin cool. Because it performed better than the day before I assumed the charge was ok and the system was under-performing for a different reason, given that it was hotter out.

So, what happened? I figure there are a couple likely scenarios. The original compressor blew up and sent bits though the system clogging the expansion valve, and perhaps the drier, being the most likely. Or, maybe I simply have a weak compressor? Too? When I did the driveway test on Sunday morning the compressor body was super hot to the touch within a few minutes, way hotter than the alternator next to it, and was making a whining sound. Even with the clutch disengaged I could hear a slight whining, it was but louder with the compressor working. I haven't hooked up my gauges to it yet, that's probably a requisite next step and will do that perhaps later today. I also can't say if the compressor was cycling because it didn't run that long. I did run the HVAC ECU Self test and got no errors.

Yesterday I decided to tackle the expansion valve on the parts truck to get a sense of the job. After extensive searching here there's not a lot of good info on what that job entails but let me tell you it's not at all a small job if anyone wasn't aware. The first bad sign is when you go to the page for the expansion valve in the RAVE it tells you to take apart the HVAC box. That however links you back to removing the box, which links to removing the "fascia". That tells you to remove to console, which links you back to removing something else first. This happens about five times. I still don't have the box out of the truck yet but below is a pic of almost where you need to be in order to "graduate" the page in the RAVE about replacing the expansion valve.

I'm not sure I have it in me to go this far in my driver and am afraid this may mean I'll never have cold air in this truck. My real question here (for anyone still reading) is how plausible is it for me to have the system evacuated and flushed and then replace the compressor with a known good one, replace the drier and refill it? In my mind, the truck is struggling under extreme conditions and a weak compressor certainly could be the culprit. I can do all that for next to nothing dollar-wise. It seems like a cheap thrill and sure beats doing this to my truck.

 

I think your best first measure before yanking out your dash would be to take it back to your buddy who charged it and have him perform a true AC diagnosis. Monitor running pressures to see if the compressor is weak, check the AUX fans to ensure they are coming on correctly, use an IR gun to shoot across the condenser to check for any hotspots(indicating a clog), verify your charge is still normal, etc.

There are many more pieces to the warm AC puzzle than just the correct charge amount

 

Probably got a leak, I’ll almost put money on it
unless you have a micron gauge you have no idea if it held vaccum

 

Seems like sound advice, thanks. I can certainly do some of that myself. I'm pretty confident the aux fan is operating correctly, it comes on when I start the A/C and was a known good component from my last truck, as was the compressor I blew up. I can check pressures myself, and IR gun the condenser as well. I didn't plan on tearing right into the dash without further testing however given the scenario, a plug somewhere in the system sounds like the most likely candidate to me. I am by no means an expert when it comes to A/C however I've done my own work on all my cars, including fabbing my own hoses, and this was the first time I've taken one to a shop for anything.

A set of gauges and a vacuum pump isn't any good to check for leaks any longer? I don't entirely disagree with the leak theory but it held -29.5 PSI for over 45 minutes so I assumed that meant I didn't have a leak. My last truck would hold that level of vacuum for about 30 minutes and then suddenly the needle would swing to zero all at once. Never had a problem with that AC and filled that one in my driveway with a scale and a 30lb bottle of R134a.

Thanks for both the replies.

 

you want a real pressure ac check leak put in 100 psi of nitrogen and see if it drops over a 2 hour period.

 

Well, pressure is different than vacuum and more realistic to the operating environment so i agree with you there. And like I said, a leak certainly could be part of the problem so I can't rule it out without further testing. That one just seemed further down the list to me given the chain of events leading up to the problem. I saw you determined you had a leaking evaporator a few weeks ago. I don't remember all the details in the thread. Where did you get that tester?

 

im a hvac/ refrigeration mechanic

 

my AC shop told me that our Juke AC expansion valve is most likely clogged. (Our Air Conditioner just stopped and its not a loss of freon) And he said the dash must be removed to change it and they don't do that. I googled for the cost of the job and the estimates were in the low hundreds, making me think he was mistaken that the dash has to come out. Has anyone changed the expansion valve and was it from the engine side?

 

I have a partially plugged expansion valve, I researched it pretty extensively earlier in the year. I am pretty sure you cannot get to the expansion valve from the engine side.

 

You cannot get to the expansion valve from the engine side. You need to remove the HVAC box and disassemble it to get at the expansion valve. It lives in here:



and is against the evaporator here, shown in the lower right:





As a follow up to the initial story, I ended up getting a can of R134A recharge from the local autoparts store, the kind with the trigger and the gauge on top, and over the last 4 years have slowly kept recharging the system. I don't remember the particulars but I'm now halfway through the second can, and each time the charge seems to last longer than the time before. Perhaps it's lubing the seals, or the magical sealant in the can is working progressively.