C-5 expansion valve?

[Corley]

OK, so I put the insurance back on the C-5 so I could use it this summer. Unfortunetly, it's not a Studebaker, but a C-5 Vette. Anyway, the A/C is not working. Just blows hot air. Being 14 years old now, (with less than 30k original miles on it) I assumed it probably needed a squirt of R-134, so I put the gauges on it, and cranked it up. Then, I noticed that the compressor was actually running (it won't run if low on refrigerant), but the lines to / from the evaporator were both hot. You can't see the TX valve on this one, it's burried in the covers, but I noticed that the pressure at rest is about 50 lbs, and with the compressor running, it's about 40lbs on the low side, and about 90-100 on the high side. No cooling at all though. So, my thought is that the expansion valve is stuck wide open. The compressor could be bad, but I don't think so, my money is on the TX valve.

Just after second opinions here, hopefull from someone who knows A/C systems well. I understand it's about an 8 hour job at the dealer to replace that valve, probably longer for me, and of course involves sucking all the R-134 out first, then putting it back. I've got the freon reclaimation machine to do that, but what a pain in the ____.

Not looking forward to replacing this part, and will also have to replace the reciever dryer, plus a bunch of new 'O' rings, etc. Can't actually see any of those items without removing stuff from the car. YUK!

Anyway, any opinions on the failure?

[Gunslinger]

Register on the Corvette Forum and ask your question there on the C5 section. There's lots and lots of good information and people there. Someone there should be able to answer your question...it may not be an uncommon issue and an answer should be forthcoming. http://forums.corvetteforum.com/index.php

I'm often on the C3 section and there's lots of others...the C5 area is probably more popular.

[Corley]

I figured it is a question about an A/C failure, not particularly any specific vehicle. Studebakers had A/C as an option, plus this is "Stove huggers"! Any A/C experts out there?

[41 Frank]

Before I would do anything else I would reclaim the refrigerant that is in the system and recharge with the proper amount of R-134A since you apparently have the equipment to do so. Then if it does not cool I would replace the TX valve or orifice as it is called.

[Corley]

Frank,

Yes, I've found that this one uses the "orifice tube" instead of the TXV, or expansion valve. For those who might not know, what it amounts to is a small hole inside a filter. It's mounted ahead of the evaporator, and basically turns the liquid refrigerant into a vapor, by causing a pressure differential. The good news is that it is located where you can get at it. The bad news is that my problem could also be the compressor, which is buried very deep. More good news is the orfice tubes cost less than a buck at Rock Auto (and other places), about $7 at the local Napa. I've orderred a couple and will replace when I get to it.

One might think that a fixed orifice in the high side of the refrigerant path would cause an explosion, or at least a terrible problem, but the thing that makes it work is that the clutch on the compressor is cycled on and off, keeping the pressure under control. A lot of GM cars, and others too, use this method since it is so simple. But, the plastic part, the orifice tube / filter, is easily clogged or broken, so it has it's down side. Here is a picture of one. Well, I WAS going to put a picture here, but I see we are back to not allowing uploads from our PC again, so no picture for you.