vettfixr

I've got a compressor that's leaking oil at the front seal and I'm probably going to replace it. While I'm at it (we all know that phrase :lol: )I'll probably convert over to R134 and if I do that I'd like to eliminate the Vir and go with the conversion kit. I've seen the conversion kit at Ecklers but I believe I can also get it from Old Air Products or one of those companies. I know it changes the system to a cycling compressor but I'm not sure whether the POA valve is adjustable. In many posts here I've heard that the adjustable POA valve is a plus when going to R134. True or False? Any help would be appreciated.

vettfixr

Nothing on this? :confused:

A C

I work on commercial A/C systems, but my 69 doesn't have it....what is a VIR? :confused:

vettfixr

Valve In Receiver. It's pretty much a combination of all the parts like the drier, suction valve, dessicant, etc.

A C

So it is a metering device and a drier all in one? The dessicant would be in the drier. In commercial systems we use a seperate filter drier and a thermostatic expansion valve, fixed orifice, or capillary tube metering device to meter refrigerant flow. I have a feeling that on C3 Vettes it was probably a fixed orifice.

[EDIT- oh and what is a POA valve?]

I am learning new nomenclature here. :D


[Modified by A C, 7:51 PM 7/3/2003]

vettfixr

I think it's the orifice valve. I was never really up on AC systems and how they work. But I think I'm going to have to become a little more informed if I'm ever going to get this system working the way I want. I believe you're right about the fixed orifice. I read in a few other posts about an adjustable orifice valve that allows the system to work better with the R 134 refridgerant. This is what I'm trying to become a little more knowledgeable about. The VIRs run about $150 a pop for a rebuilt unit and they're really set up for R-12. I think by changing the system over I might be able to get reasonable cooling with the new refridgerants.

Smokehouse69

Check out Zwede's web page http://www.corvetteforum.net/c3/zwed.../ac/acmain.htm he has a 71 that he converted to r-134 a couple of years back. I know that he did something with the POA to get the R-134 to perform better.
I'm going to go with this stuff instead of R-12 or R-134, I found out the new refrigerator in my house uses the stuff, so I'm going to try it in my car. I know a couple of guys that are using it and they say their A/C's will freeze the ***** off a Christmas tree. It requires no changes to your R-12 system at all!
http://autorefrigerants.com/co00033.htm


[Modified by Smokehouse69, 8:25 PM 7/3/2003]

A C

Steve, the only things that you need to really know about R-12 replacement refrigerants is if they are compatible with the R-12 oil (VERY important), and if the pressure/temperature relationships are close. Hot shot was within a degree of R-12 on most of the p/t charts I saw, but it was only half the cost of R-12, which still put it at about 14-15 bucks a pound.

Vettfixr....I am surprised someone doesn't have a regular fixed orifice device out for C3's to run 134a.

Adjusting metering devices can be tricky...you need to make sure your evaporator and condenser coils are clean, and that both fans (the blower fan and the motor fan) are in good shape first. That would give you the best starting point to play with the adjustable orifice.

vettfixr

I just went through my system last year and rebuilt the entire heating and AC system. Everything is in good working order and I replaced the VIR at the time and installed a rebuilt compressor. It cost me almost $200 to have the system charged then and I don't think the guy that did it knew what he was doing. I think he overfilled the oil and that possibly is why I'm having a problem with the front seal. I'm going to replace the compressor with a chrome unit (have to maintain my "King of Chrome" title :lol: ) and then recharge the system. If the Envirosafe is compatible with the system as it sits I won't have to change anything else and that appeals to me. I'll have to look into it some more.

mrvette

OK, the short answer is that Zwede rrecommends the adjustment bolt in the output/discharge end of the new POA valve be turned 1/4 turn counter clockwise,...he says it's worth 10f drop in discharge temps with R134....vs leaving it alone...

as you know there are many generations of the GM a/c stuff, not just in vettes, but across the line, inclucing the unfortunate R4 compressor that most guys swear rebuilts are no good....personally I"v never had troubles with a rebuilt R4, or A6...which is that heavy long thing like found originally on my '72.....now I have a serpentine setup, and an '88 up vette style compressor....works fine....with the original setup the way GM plumbed it....
compressor allways on, no cycling...

NOW I found out about Zwedes mods to that POA valve some years ago on here, and forgot to modify it when I did have the system down some years ago, oh well...it's ok still.....
I forget exactly the meaning of the letters in POA, but it's function is keeping the refrigerant in the evaporator long enough to warm up and metering the flow back to the compressor, as the compressor can/will at higher speeds suck the freon out and loose cooling effect that way....now the later systems had in place of the expansion valve, which has that wetbulb stuck on the suction side of the evaporator tube there...that large 3/4 inch aluminum pipe...
the expansion valve made sure the evaporator was allways full of freon, as measured by the discharge temp....so the pressures were regulated well....

NOW later years they decided to do something differant and make the expansion valve into a fixed orifice tube, on the input side of the evaporator, that 1/2 inch pipe, and it's inside the closese connecting bolt off that pipe...looks like nothing there from appearances....it is.... I know a '78 vette was set up like that, has NO POA valve either, and in fact has a pressure cycling switch maybe two...been some time,...that they interrupt the compressor signal so either the high side or the suction side are allways in balance enough to get decent cooling,
the later vette expansion orifice tube is a white plastic thing with a long skinny screen on it....when you pull it out you will see it's most likely full of crap on it, indicating contamination or wear in the system plumbing....
maybe even rings from a compressor...be amazed the damage I have seen on compressors.....when tearing them down to have a look see.....

the VIR systems like said above has 2 valves and the dessicant in that cannister.....it's a relatively short production run of about 3 years in the mid 70's....which also included Vettes.....not sure of exactly which years or parts of years.....I have seen all sorts of date changes involving that crap in various GM cars over those years.....pardon ME, I can't keep it straight....

GENE

FeedVaal

Fortunately, I didn't have to mess with a VIR device (Valve In Receiver) on my 77 when I converted last year to 134a. I tried enviro-safe and Freeze-12 as drop in replacements and was unsatisfied with the 60 degree vent temps at acceptable high pressure levels, so I flushed the system and replaced the drier and compressor (R-4) and spent two days getting the thing to hold vacuum. If I were doing it today, I would replace the compressor with a Sanden unit (Yes, they come in chrome too). I used one of those fancy variable orifice valves but I think I would have been as well off with a Ford blue .054 valve. I learned everything I needed to know on the internet. I also learned there is a lot of misinformation out there too, so take it all with a grain of salt.