Help me make sure it's an A/C compressor failure

If nothing changes when you turn the A/C on, then it just means that your compressor clutch is not kicking in, and thus your compressor is not running. This can happen for various reasons, including low refrigerant. Do you still have the yellow jacket manifold gauge set? I can help you figure out how to "read" what it going on (or at least I *think* I can).

But there's a list of other stuff that's more about electrical / sensor issues. The system has a low pressure switch that will kill the compressor clutch if the refrigerant pressure is too low (it protects the compressor). If the refrigerant levels are ok, but the system doesn't engage that switch might be bad or stuck. It might also have a problem in the wiring.

Then there are the internal controls. I confess that I don't know - electrically speaking - exactly how that A/C switch/button works. I suspect that if it lights up green it's probably ok, but maybe not and it's not sending the "on" info to the car.

Then there's the wiring that actually sends power to the compressor clutch...

In any case, I found the thread you were on last summer and I actually suspect that you have low refrigerant - so low that the compressor won't kick on. If you still have that yellow jacket set, pop it back on. Fire up the car, turn the A/C on full blast / MAX and report back.

Unfortunately for you, if that's what it comes down to you may be stuck with a shop visit. It will mean a) that you do have a leak and b) that your system is now probably over-contaminated with moisture. So the only way to fix it for real is to replace all of the seals, the expansion valve, the drier components, and have everything completely cleaned up, re-assembled, vacuumed and properly refilled. It's not a picnic and very unlikely something you can do when you don't have a place to work on the car.

P.S. Oh, and skip that local repair shop. Your problem is very likely NOT that you need a new compressor.

 

I didn't have the impression that she tried to turn it by hand. Sandy? Did you try to turn it by hand? This would be that outer disc, not the pulley itself.

Agreed that finding out if 12V is being sent to the clutch is a good next step. Multimeter or even just a 12V test light.

 

Ah yes. The one from back over the weekend. My bad. (I was looking in her most recent post). At the time I actually just figured she tried to turn the whole pulley. But an important clarification is to know what she tried to turn.

 

Thanks Ron. I think that if I decide to do the compressor I'll skip a used one, and at least go for a reman. I actually did look up rebuild kits on rockauto and found them surprisingly affordable - compressor, new drier guts and expansion valve (as I recall) for all of $250-300 or so.

 

I bit the bullet and bought a manifold gauge set. "Bit the bullet" is a little extreme as it's an "A/C Pro" retailed at many AP stores for around $100 and I got a $20 discount so only dropped about $84 after tax.

Anyway...with everything off, including the car, ambient temps at 88F and about 50% humidity (and in the shade), I had both hi/lo sides reading 120psi. (The car had been in the sun before moving to shade, but it's also white and hadn't been run for a good 18 hours). That does seem high as the charts I find say it should be more like 100psi. Do note that I've had the car 2 years with working AC and no one, including myself has messed with it. So I don't know what to make of that.

So I start the car, crank the A/C - max setting, hi fan, defrost mode. The low side initially drops to only 95, and after about 5 mins has slowly drifted up to 100. The high side didn't really budge- stayed at 120psi. So to me this looks like blown compressor.

So after about 10mins I shut it all down. A/C off, car off and I'm just watching the gauges expecting them to just equalize back at 120psi per side. But that's not how it went down. The high side barely moved, but the low side pressure shot off the chart. I can't tell you how high it went. After going in 10psi increments on the whole gauge, after 120psi the low side gauge goes to 350psi in the same amount of space. After shut down, the pressure slowly climbed and pinned itself past what the gauge said was 350psi. This pic was while it was gradually climbing:


You have to forgive me. I was a D student in chemistry and only a C student in physics, so I have no idea what to make of that except that perhaps what the compressor was doing better than "compressing" was just making heat. IDK what temps it takes to get 134a to 350+psi, but maybe whatever heat the compressor made?

Anyway, I just left the gauges on ... kept my distance ... and after about 1.5hrs it all finally came back down to 120psi both sides.

I probably see an A/C shop in my future as it's obvious that I have no idea what I'm doing...but, uh. If anyone knows what I'm looking at all the better. Thanks.

 

Well, I made a decision that I'm not taking this thing to an A/C shop. It's a near-20yr old car w almost 200K on it and professional A/C work costs a fortune. (Not saying I resent paying for the expertise - just that this car isn't worth it. I could sell it for as much as a shop would cost).

I did figure out on my own that what it takes to get R134a to about 350psi is about 185 F - which...you know is right around the ICE coolant temp. And ... I also figured out that the condenser is integrated into the radiator. So maybe that explains the shut down high pressures? Though I still don't know why the high side pressures never moved.

But, in any case, I can buy an overhaul kit for about $250 - new (not reman) compressor, expansion valve, and new desiccant guts for the drier. I can figure out the recovery of existing refrigerant & refill. And if the condenser wasn't integrated into the radiator, I'd think about doing the condenser too. But since it is integrated, this is now another $250 minimum and a bunch more labor/hassle.

So I guess the question is about the condenser. Obviously there is no certainty about answers since who knows what went on inside of my system. But generally speaking, how likely is it that the condenser is so buggered that it will be a waste of my time & money? If I do this I plan to do an autopsy on the compressor and if it has obviously shed noticeable amounts of metal, then that's quite relevant. Or if there are other signs of contamination like sludgy stuff.

Guess I'm just looking for past experience from people who have mucked around with these A/C systems. Thanks.

 

Thanks so much for your input. What's funny is that 99/100 on an auto repair board I'm the guy saying what you're saying so I know exactly where you're coming from.

But a little about me. The newest car I own is a 2006 and it has 230K+ miles on it. And its a Saab (death wish)! The 2nd newest car I own is the '03 Prius. Under that I have an '02 GMC Envoy (nearing 180K), a '97 Ford Ranger (nearing 240K) and - don't laugh - a '97 Escort with over 450K on the body (and many of the parts. But don't get me started on Escort valve seat insert issues - 3rd engine, 4th cylinder head).

I buy old "used up" (by normal standards) vehicles that haven't been abused and keep them on the road. And it pays off. As compared to most, I spend very little on autos. The last time I had a "car payment" was something like 1993. My insurance and personal property tax payments (a thing in Virginia) are dirt. The trade-off is obviously that I sometimes have to spend some $ on parts and some time working on them. The Envoy just got new upper and lower ball joints on both sides, for example. I figure that even if I add in my labor costs at an optimistic rate, I just saved $800-1000.

And over the years, I decide when to "graduate" to new levels of knowing how to do stuff. The Escort is still on the road because - and only the latest part of the Escort story - I pulled the head, ground the valves by hand - just to see how it works - dropped the oil pan, pulled the pistons, gave the bores a hone, the pistons new rings and the rods new bearings (including checking specs with ye olde plastigauge). And a lot of that just to see if I could do it and to understand how it works. I'm pretty sure I can grapple with the trickiness of A/C systems. Just haven't put my mind to that yet.

Of the 5 cars I own 2 now have working A/C (the Saab ad the Envoy). So this is not a one time shot. Auto A/C systems seem to be to most fragile things on the planet (2nd only to Trump's ego) and the most expensive to fix. It's not my first go-round with a broken one. They are totally under-engineered for long-term reliability and they just piss me off. So I'm just about where I'm ready to know how to fix them.

So you're right that I've made my decision. I'm not flying blind, by the way. My compressor is engaging but apparently not actually "compressing." A shop is going to quote me for compressor, expansion valve, receiver drier and - probably - condenser, and - probably - all new seals through the system. $2K at least. Really? And they'll charge me a minimum $100 for the pleasure of telling me what I already know. So I'd rather sweat. I couldn't sell this thing for $2K. All I'm talking about spending $250 and some of my labor while I "graduate" to learning about yet another realm of auto repair that will benefit me as I move along. If I fail? So what? I spent not very much to get right back to where I already am. A loss, sure. But I will have learned. And I can't break it any more than its already broke.

 

Thanks so much for taking the time to respond.

I have to wonder though. Are you under the impression that I tried to "recharge" my system with cheap AP parts store stuff? I didn't.

I bought the car in August 2018 with working A/C. It was working fine until this summer - so a good 18mos. Sure - I threw my cheap AP store "recharge" gauge/can on it. But the only problem I found is that the low side pressure was completely indifferent to the compressor kicking on. I added no refrigerant.

So, I figured my compressor was dead, but ChapmanF was so sure that this was implausible that I went to buy a full manifold gauge set (which I've always wanted to anyway - this one was just the last straw). Not as fancy as your computerized one to be sure. But the hi/lo side pressure results with a continuously running compressor are up there in post #29.

Summary:
- My A/C worked until very recently for almost 2 years.
- I added no refrigerant.
- My compressor will run continuously if the A/C is set to on. Not just the pulley. The clutch kicks on and off as it should if A/C is turned on/off. I know what it looks like. I know what it sounds like. But the low side pressure with compressor on barely moves. The high side - even less.
- On the advice of ChapmanF I turned the clutch by hand with car off and it moves easily and is quiet. It is also not making any noise with the car running / A-C on / clutch engaged and compressor running. It just goes "clack" on, spins as it should with no weird noises and and "clack" off - if you shut it off. That's it. Period.
- The system gives me no error codes (i.e. it's not as simple as the clutch.)

I will likely have a shop recover existing refrigerant and the refill, if that's the point. But if I do the recharge, it will be to spec in terms of oil and refrigerant strictly by weight.

 

Thanks again for offering up your input. It is completely valued. It's weird how much of their time complete strangers will give to each other on the web to try to help each other. In such weird times where it's easy for us all to lose faith in each other, it's nice to verify why we should not ;-). So, yeah, just thanks.

If I do this project I will absolutely follow up with experiences and pics. Of course, all I can think right now is ... shade tree or not it's too damned hot out there to be working on a car! Ironic, though, given what I need to fix...