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Old 09-15-2010, 07:12 PM   #1
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VX A/C issue

Recently converted my 1992 Civic VX from R12 to 134a. The compressor safety valve vents pressure. My mechanic says it needs a new compressor.

The following is from a CRX forum.

I expect the reason several people have had troubles with blowing safety valves is because R-134a systems run at higher pressure then an R-12 system that the compressor and safety valve are designed for. When you run at normal pressures for R-134a your often near the safety valve pressure. Proper R-134a conversions include a high pressure cut off switch to disengage the A/C clutch when the pressure is getting too high. The high pressure cut off switch is often omitted during conversion and more often then not people get away with it. Even if only 1 out of 10 converted systems has high pressure issues that would mean a lot of them are going to blow.

I expect the over pressure issue is most common in hotter climates where the system pressures run the highest. I think the options are:
1. Install a high pressure cut off switch.
2. Run a lower charge of R-134a to try and limit system pressure.
3. Use an alternative refrigerant that runs at a lower pressure. I'm planning to run ES-12a (Enviro-safe) in my car.

I have heard that the safety valve often does not reseat well after popping so a replacement is probably required.

Any thoughts? Advice?
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Old 09-16-2010, 02:45 PM   #2
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Re: VX A/C issue

Do you live in a "hotter" climate?

Did YOU do the R-12 to R-134A conversion?

Your mechanic is the one saying the compressor relief valve is leaking and needs to replace the compressor?

I bought a 92 VX five years ago with an A/C system with the compressor removed - presumably because it failed and the owner decided he didn't want to repair it. I bought a used compressor and reinstalled it. It was a lot of work AND I retrofitted the A/C to R134A at the same time. I bought a vacuum pump and an A/C manifold gauge to read the pressure while I did the repair and refit work. I DID use the recommended o-rings at all fittings since the R-134A molecules are smaller than the R-12 molecules.

I have not experienced ANY issues with the compressor relief valve releasing pressure - EVER. I have not had any problems at all with the R-134A EXCEPT that it doesn't cool as efficiently as the R-12 did in the first 92 VX I owned for ten years without any issues except for a R-12 recharge after 8 years of ownership.

What I do have is a problem with leaking schrader valves at the high and low side service ports on the condensor. I couldn't pull the schrader valves out (I was afraid to FUBAR them), so I screwed on metal caps with o-rings and teflon tape to slow the leakage through them. I do need to add R134A every two years.

The A/C in old Honda Civics are not very good compared to large cars like my Buick LeSabre - that A/C got ice cold even when the temperature was 100 and it had an R134A system.

However, I do live in Michigan where A/C is only needed from mid May to late September.

I know a great deal about A/C now that I repaired mine. If you could describe the problems you are having in more detail I might be able to help you.
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Old 09-16-2010, 03:12 PM   #3
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Re: VX A/C issue

I highly recommend the R-12 replacements on the market instead of the R134 conversion. The R-12 replacements run at lower pressures, and are actually colder than R-12 originally was. My dad used it on an old system he didn't want to waste R-12 on, and it worked great.
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Old 09-16-2010, 04:48 PM   #4
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Re: VX A/C issue

ALTERNATIVE REFRIGERANT BLENDS

Alternative refrigerants that have been found acceptable for automotive applications or are currently being reviewed by the EPA include the following blends:

Free Zone (RB-276). Supplied by Refrigerant Gases, this blend contains 79% R-134a, 19% HCFC-142b and 2% lubricant.
Freeze 12. Supplied by Technical Chemical, this blend contains 80% R-134a and 20% HCFC-142b.
FRIGC (FR-12). Made by Intermagnetics General and marketed by Pennzoil, this blend contains 59% R-134a, 39% HCFC-124 and 2% butane.
GHG-X4 (Autofrost & McCool Chill-It). This blend is supplied by Peoples Welding Supply and contains 51% R-22, 28.5% HCFC-124, 16.5% HCFC-142b and 4% isobutane (R-600a).
GHG-HP. Also supplied by Peoples Welding Supply, this blend contains 65% R-22, 31% HCFC-142b and 4% isobutane (R-600a).
Hot Shot\Kar Kool. Supplied by ICOR, this blend contains 50% R-22, 39% HCFC-124, 9.5% HCFC-142b and 1.5% isobutane (R-600a).

Sure, R134A has 10% more pressure at operating temperature than R12 but at least it's not a blend like those above.
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Old 09-16-2010, 04:55 PM   #5
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Re: VX A/C issue

Dad used one of them that was made out of butane, not sure which one. It sure was cold though.
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Old 09-16-2010, 05:04 PM   #6
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Re: VX A/C issue

Did he own a land yacht like a Cadillac Fleetwood, a Buick Roadmaster, a Chrysler Imperial, or a 1968 T-bird with suicide doors? Now, THOSE were cars.

Man, sometimes I really miss those days - and the Woodward Dream Cruise just ended.
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Old 09-16-2010, 05:21 PM   #7
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Re: VX A/C issue

Jay, see if you can find out exactly which product was used.

jadziasman, those days are back...for me. Once I get my project on the road I'll be posting a thread about it to find out how I can maximize its fuel economy. It's not as crazy as it sounds...
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Old 09-16-2010, 05:25 PM   #8
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Re: VX A/C issue

No, Grandpa & I were the ones in the family buying land barges.
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Old 09-17-2010, 09:37 PM   #9
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Re: VX A/C issue

Jadziasman,

Yes I live in Florida. No, I had a former Honda dealer technician with his own business install the kit but he tried to gouge me on parts and said I needed an evaporator. So I took it to my trusted tech who is much farther away. The compressor is original so we decided to replace it with a rebuilt one. The pressure indications were off and it was making unusual noises so he is taking it back. No leaks though, evaporator is good.

Sounds like I should have used an R -12 replacement instead of 134a. Thanks for the help everyone, I learned a lot.
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