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AC Expansion valve?

So that CRV I got yesterday also did not have working AC. I was hoping it was low on R134. So I got a can from the autoparts store with the built in gauge. Hooked it up and started filling the system (I know it was not completely empty as I tapped the low side shrader valve and got some pressure). Well the pressure jumped like it usually does when I opened the fill valve, and the compressor kicked on as you would expect. However the pressure never dropped, and by te time I turned the can off it had spiked the gauge. So I dug my real gauge set from the garage. Hooked it up and am showing 85 on the low side and about 110 on the high side with the compressor running. I’m thinking bad expansion valve. What are your guys thoughts??

Also if I rev the motor the air will get cool not cold but noticeably cooler. As soon as it goes back to idle it’s warm again.

A bad expansion valve would see a spike in high pressure on the high side. The low side would also drop. The compressor is working, but the gas has no place to go. High side pressure that low points to a bad compressor.

See I don’t think the system is full, i only put in around half a large can. How can I tell compressor or expansion valve?

I guess you will just have to replace the expansion valve and see…If the valve opening is too large, the freon has nothing to build up pressure against and the freon just gets pumped 'round and 'round…But on your gauges, a bad compressor will produce the same readings…Since the “valve” is really just an orifice of fixed size, the chances of it reaming itself out are pretty slim…Depends on the design I guess…

Well this thing has 230,000 miles on it, so anything us possible. I only paid 850 for it, and it runs and drives great. Is totally rust free and after a good cleaning will look fine. I still have a hard time thinking it’s the compressor, as it sounds fine. But I guess it makes sence.

The big A/C shops have a test-bench for compressors so their performance can be verified. For the home mechanic, accurate testing is difficult. I have seen expansion valves get plugged and high-side pressure soars, the high-side limit switch shutting off the compressor…But I have NEVER seen one blow open internally and prevent the compressor from creating the necessary LOW / HIGH pressure difference because of free-flow in the loop…

Perhaps one of the A/C experts will join in…

You’ve got a failed compressor. Running pressures like your almost certainly indicate a failed compressor. Shut the car off and let the pressures stabilize and equalize. Then start it and watch what happens. I’ll bet the pressures only change marginally. An expansion valve stuck closed would give you very low side pressures. I’ve never seen a stuck open valve.

Is there a sight glass on the drier?

I’ll bet if you try to turn the compressor clutch by hand with the engine off it’ll turn pretty easily.

Ok so it seems the compressor is bad, I’m guessing it’s age. Do I still need to flush the system?? If so how can I do it. I will get a new dryer of course, but what else can I do??

The expansion valve is pretty much a two-state device…allowing flow or no flow based on temperature. The orifice size remains constant and would never become huge all of the sudden. As stated if pressures equalize instantly when the A/C is turned off then the compressor is faulty and likely tossed some of it’s cookies forward to everything else. Yes, flush and flush and hope you flushed it all.