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

When you have the car turned completely off, and reach in and rotate the clutch pressure plate (the bit showing the triangular center pattern here) by hand, how does it feel?



The pulley will not rotate easily, because the belt is around it and the engine is stopped, but the center pressure-plate portion should easily rotate by hand, because of course it is disengaged. It should feel as if you are turning a smooth well-oiled machine.

 

Okay, I’m back at this same issue on my 2001 Prius with 98,000 miles . This time I’m in cooler weather, not Palm Springs at 100+. It’s an overcast day here in So Cal.

I have zero diagnostics. No blinking of the A/C button above based on the above testing. I’ve had a scanner on it with no codes thrown.
I do have heat churning out if that matters.
I cannot hand turn the part indicated above.

Last time I was at Prius Chat in June a year ago I felt like I went down a rabbit hole here — too complicated for me under 100*. I got a Yellow Jacket pressure manifold and tried to put the correct Freon in but don’t know if I was able to properly connect. The set-up connections were right. It was so frickin hot my brain was fried and I am guessing I don’t have strength in my hands to properly attach the couplers to the inlet port etc. I bought correct Robinair couplers too. Pressures were wacky or nonexistent even after attempting to fill so maybe I don’t know what I was doing. But there was pressure release coming from the vehicle when I attached the manifold which tells me there was Freon in the AC.

The Car AC has never been serviced. I am original owner.

Any ideas now? Seems like I’m in same boat as the original poster. Many thanks.

 

Well, or a similar boat, maybe. Or less similar; a lot of details could turn out to be different; the turn-the-pressure-plate test could even be one of them.

My follow-up question to that would be, now with the engine started and a call for cooling, what do you see it do? With the engine running, the pulley around that center plate will be spinning. Under normal conditions, with a call for cooling, that center plate will pull inward toward the pulley, with a clack sound, and start spinning along with the pulley. What does yours do?

 

I don't know much about ACs in general, but I wonder if you have a vent issue, maybe an actuator not opening a vent to let the cool air inside? On the positive side, these compressors are the easiest to replace I've ever messed with.

 

If you can't turn that part, I'd expect the compressor is locked up. There's another common issue when it turns on and off caused by the clutch plate needing some more shims to help it spin the compressor; it's an inexpensive fix. But I'd expect it would still spin by hand when off if that were the case.

 

You might also read up in threads here about those shims. It will cause the clutch to AC to turn on and off as far as cooling, but I'm not sure whether the clutch keeps spinning to the naked eye, but just isn't actually able to grab the shaft to spin the compressor.

 

Well, the title says to help you make sure it's a compressor failure, but at this point I'mnot sure I would say that.

Easy spinning of the pressure plate by hand sounds good. I trust you didn't feel or hear any roughness or sense of stuff broken inside? A scroll compressor is mechanically really simple; there are some pictures on PriusChat showing chunks broken off inside failed ones, but if you didn't feel anything weird I wouldn't assume that has happened.

The blinking light or 22 code would be signs of clutch slip: the A/C computer looks at the rpm of the compressor shaft (there's an rpm sensor there). Because it knows the sizes of the pulleys, and it can get the engine RPM by asking the engine controller, it can calculate the rpm the compressor should be turning. If the compressor is turning slower than that (as if the clutch doesn't have enough friction to transmit as much work as the compressor is doing), then you would get the code.

In your case, it sounds like the compressor just isn't doing much work, so it doesn't take much to turn, and the rpms through the clutch are holding up fine, hence no slippage code.

All of those observations to me seem consistent with not much refrigerant being in there, and that being why the compressor hasn't got a lot of work to do. Enough refrigerant to make the low limit of the switch ... or, maybe, the low limit side of the switch is stuck on. Have you checked for that?

The one piece that isn't fitting for me would be the gauge readings you mentioned in the first post. 120 psi strikes me as high. When the system is off and equalized, you should see the equilibrium pressure for R134a at the surrounding temperature. Ok, so I guess that could be in the ballpark if the temp was 98℉ at the time. Does that sound right?

That equlibrium pressure doesn't really tell you how much refrigerant is in there ... you will always see that pressure with that temperature whenever there's enough in there to be part liquid and part vapor. Doesn't have to mean there's much of it.

So I don't know if there might have been something odd about technique when taking those earlier measurements.

@lech auto air conditionin might have more ideas here. I think a lot of ideas from here out might involve having the ability to evacuate and recharge (even testing the pressure switch, 'cause I don't think there's a Schrader valve under it), which might mean an A/C shoppe will be best equipped to find an answer quickly.

 

That is weird, but a scroll compressor is so simple I can scarcely picture a compressor-failure explanation for that, short of the scroll being broken clean off inside yet not feeling at all chunky when you spin it, which boggles my mind.

Paging @lech auto air conditionin ... maybe that happens more often than I think, or there's some other likely cause he would know about.

I still want there to be some piece of this picture I'm just not picturing yet.

 

Don't waste your money on a manifold set from Harbor Freight. I messed with mine on my truck for a while before I figured out it was leaking somewhere.

 

A system generally will use one or the other. My old Bronco II used an orifice tube. A Prius has an expansion valve.

A stuck-open expansion valve and a blocked orifice tube are pretty much opposite things.

By the way, in case it comes to the expansion valve, Toyota built in a shortcut for removing the blower housing (needed for access to the valve) without taking the whole instrument panel out.

There is a plastic crosspiece below the glove-box door that can be cut in two places (marks for the two places are molded right in). When cut in those two places and removed, it allows the blower housing to come out even with the dash in place.

After putting things back together, there's a little metal brace as a repair part. It has screw holes that line up with molded-in screw locations near the two cut points, so it installs with screws right where the cut-out piece was, good as new.

 

Probably, but it's buried in the garage somewhere now.

 

I hear that. I don't mind so much letting someone else do the work when I know what needs to be done, or if I still lived near Dallas where I had two different very honest techs. But going into an unknown shop or dealership not knowing what's wrong is terrifying. It's why I have several cars that aren't running right now even though I know it's just something minor. Minor to a tech means $2000.