Automotive Air Conditioning Information Forum

Hello, my AC went out and was blowing only hot air. I pulled a vacuum on it and it holds. I went to add R1234YF to it and messed up and had both low and high side valves open on my manifold gauge set when adding my first of about 2.5 cans needed at about $60 per can. When I realized I had the high side valve open, I closed it and the pressures at this point were about 70 psi. I continued to add that 1st can having to warm it up, shake it and turning it upside down and right side up to get it all in there as I could feel the remaining refrigerant still in there shaking around. I finally got all of the 1st can in there, but the weird thing is, the high side matches the low side still and they're both at about 110 psi. The ambient temperature outside was 91-92 degrees. I never saw the compressor clutch engage so I suspect bad compressor. Does anyone know what pressure the pressure switch should allow the compressor to come on at? Feeling the air come out of the vents, it's blowing hot air with AC on lowest setting and fan on highest setting.

Thanks,
Greg

greghamilton wrote: ↑Wed Aug 30, 2023 12:54 am I never saw the compressor clutch engage so I suspect bad compressor.

Wow - I'm not an AC professional, and first thing I would've done was check to see if the compressor was engaging. I wish you had done that on yours as initial step.

I actually encountered this VERY SAME situation yesterday in my 1998 Frontier that had sat for a month. I pulled over, opened the hood, saw my compressor drive plate was engaging, but no cold air. Once home, my static pressures were about 70 psi on both sides but once engaged, the pressures on both sides were low, I had lost some R134a.

greghamilton wrote: ↑Wed Aug 30, 2023 12:54 am I finally got all of the 1st can in there, but the weird thing is, the high side matches the low side still and they're both at about 110 psi. The ambient temperature outside was 91-92 degrees. I never saw the compressor clutch engage so I suspect bad compressor. Does anyone know what pressure the pressure switch should allow the compressor to come on at? Feeling the air come out of the vents, it's blowing hot air with AC on lowest setting and fan on highest setting.

I would think 110 psi would plenty high enough to "close" the pressure switch. You need to diagnose whether the AC compressor is not engaging (even CAUTIOUSLY and CAREFULLY tapping on the compressor drive plate with a wooden stick, be careful of moving belts and fans) or if the pressure switch is bad or if the vehicle computer needs to be re-set.

So this might be out of your experience base, since you apparently didn't first check for AC clutch engagement, and the cost of 1234yf.

Agree with the comments immediately above.

Moreover, with the compressor not running, there's no way to get all 2-1/2 cans into the system because the pressure in the cans and in the system would become equal (approximately 60 PSI) at some point.

So what caused the AC to quit?
Leak?
Compressor grenaded?
System will hold vacuum evidently, but it can hold vacuum and still leak under pressure, and vice versa.
If comp grenaded (did you hear any bad noises?) then you also need to replace the condenser as well as the comp

greghamilton wrote: ↑Wed Aug 30, 2023 12:54 am Hello, my AC went out and was blowing only hot air.

When you say "hot air," do you mean heated air or ambient air?

Hi Cusser, thanks for that. Yeah, I guess I left out that I was not a AC professional either. I wish I had done that first too. With the system empty, I knew I would have to trick out the switch to even get it to come on and the switch was not in the same place as my last truck. That stinks. Sounds like you may have a leak. Does tapping the compressor sometimes get it to start working again?

Hi JohnHere, thanks for the info. Yeah, that makes sense. When I said hot air, I mean it is hotter than the air outside. Not sure if because blowing over and through a hot engine or something else like you may be thinking about.

Hi Tbirdtbird, yeah, I really wish I knew. I sure don't remember anything about a compressor grenade or any loud noises. I thought I had a leak initially, but then found out my gauges had a slow leak. Thanks for the info on the condenser. Sounds expensive, might need to get a new truck.

greghamilton wrote: ↑Thu Aug 31, 2023 5:05 am Hi JohnHere, thanks for the info. Yeah, that makes sense. When I said hot air, I mean it is hotter than the air outside. Not sure if because blowing over and through a hot engine or something else like you may be thinking about.

You might have a separate issue that's called "reheating," in which heated air (from the heater) is mixing with cooled air from the evaporator plenum. But if the compressor isn't running, that's the issue we'll have to address first. Have you checked the clutch gap as previously suggested? It should be around 0.020".

Condensers, if you need one, are truly not that expensive. Please remember that Tim, the site owner here, has good parts at good prices at his other website, ACkits.com, Way cheaper than another truck

You might have a separate issue that's called "reheating," in which heated air (from the heater) is mixing with cooled air from the evaporator plenum. But if the compressor isn't running, that's the issue we'll have to address first. Have you checked the clutch gap as previously suggested? It should be around 0.020".

JohnHere, thanks for the info. Honestly, as someone said before, I'm probably in over my head on this one. I was hopeful it would be a simple refrigerant refill or replace an easy part to fix a leak and then a fill, but it's acting like it's something more and I'm tired of working on it every minute of my days off and not getting anywhere on it. It's my only vehicle other than my wife's and I'm still working, so I can see a scenario where I'd have it jacked up and not even be able to get to work. For now, it's easier to just roll down all the windows and drive fast even though I live in the Dallas area, but you'd be surprised what an 80 mph windchill can do. Thanks for all your help.

Condensers, if you need one, are truly not that expensive. Please remember that Tim, the site owner here, has good parts at good prices at his other website, ACkits.com, Way cheaper than another truck

tbirdtbird, thanks for all your help too. I appreciate the information. I'm probably going to give up the ghost and make somebody a rich man.

Don't give up just yet. It might be something relatively simple.

Check the clutch gap next. If it's too wide, the clutch won't engage and hence, no cooling.

That's what Cusser alluded to when suggesting that you tap on the front of the clutch. Sometimes, that's enough for it to engage. Whether you can get a feeler gauge in there is the question.

If the gap is too wide, you'll have to remove the front clutch driven disk and take out one of the shims, thus reducing the gap.

Of course, you'll now have to recharge the system, which should be relatively easy with the compressor running.