C2 A/C

[john pickens]

I would appreciate a quick survey from all interested. My C2 has been converted
to R134 A/C refrigerant. Even filled and leak tested, performance is marginal. Not sure but dryer looks original as does condenser and compressor.
The question: how many would tweak retrofit system by replacing components and how many would revert to R-12? Thanks.

[Jack H.]

Re: C2 A/C

Think I'd first apply science to understand what's up with the current system before diving into a conversion back to R12.... There are two issues here: (1) absolute temperature, and (2) forced convection air flow.

Corvette wasn't known as a 'big blower' compared to today's A/C equipped cars, so there's little that can be done in department two regardless of the refrigerant used to plumb the system.

As far as temperature drop goes, that's pretty straight forward. R134 ought to come 'close' to R12 and you test by following the service manual diagnostic text. Crank the engine up to 2000 RPM and allow the system to stabilize. Bear in mind it takes time to 'swamp' residual heat out of the plenum....

When she's at steady state, stick a thermometer in the RH dash outlet and read the cooling air exit temp. Outlet air temp ought to track ambient in the following manner as described in the Corvette shop manual

Ambient 70F 80F 90F 100F 110F 120F
Outlet 38F 38F 40F 41F 43F 45F

If you don't come 'close' to these numbers (say within 5-10F), then there's a system problem to track down and fix (plugged suction throttling valve, defective expansion valve, Etc.).

[Randy Swartout]

Re: C2 A/C

I agree with Jack, make sure the R134 system works first. The R134 system is supposed to operate at higher pressures so you may need an ac tech to adjust the STV valve. Shop manual gives STV pressures for R12 a good ac tech will know how to compensate for the R134. I'm told it has to be jacked up a bit. At best I've been told same as Jack states, you will be 5-10 deg below the R12 temps with a proper R134 system

Original driers have a slight taper at bottom. If you have to open the system up consider replacing the drier or the desecant in the original drier if originality is important. This has nothing to do with temp, just keeps moisture out of system
You say it has been converted. Did conversion include compression refrigerant hose fittings due to r134 higher pressures? With R134 you can tolerate more leaks because it is cheaper. With R12 at $60 a pound you don't want many leaks.

One univeral "no no" I've heard is restrict your choices to R12 or R134. There are some drop in replacements for R12 that aren't thought of highly by the AC professionals I talked with.

Good luck and may all your leaks be small ones.

[Jack H.]

R12 Replacements....

are thought of HIGHLY by our chapter's HVAC professional! But, you need to study/understand which of the generic replacement refrigerants should be used in what application. Most of the commecial freezers in grocery stores are R12 based and that's a HECK of a potential loss--we're not talking about a simple 4-lb auto system capacity; we're talking 100's of lbs!

My wife's liquor store was converted from R12 to Forane 409 eight years ago and has been running tip/top ever since. But, you wouldn't want to use Forane 409 in a Corvette. The head pressures are higher and the A6 compressor is equipped with a safety purge valve to protect itself. This refrigerant will 'tickle' the compressor's purge valve and you'll lose refrigerant naturally.

But, there are other R12 substitutes that work well in A6 or R4 based automotive A/C systems. Drawback is most States require either the fittings be changed OR a prominant system label affixed so the substitute isn't mixed with R12 at a conventional auto A/C shop. Also, most auto A/C shops practice under a limited license (only able to merchant R12 or R134), so you're SOL if you need to pull over for emergency service on a cross country trek.

But, few of us actually drive our classic Corvettes that far these days. So, getting a partnership relation with a fully licensed HVAC mechanic in your home town CAN save you substantial $$$.

Also, you can use the generic substitute for a LIMITED term. Put it in for only a month or two to verify the system holds refigerant and works A-OK. Then, dump/purge and re-fill with the real McCoy R12 once you've got confidence in the system's integrity.

[Larry Rosamond]

Jack, your wife has a liquor store?

That's almost as good as owning a Corvette! Really appreciate all the input you so kindly provide.

Regards, Larry

[Jack H.]

Ex-wife for about a year now.... *NM*

[Don H.]

Re: C2 A/C

I had 134 in my 65 and it worked fair. After replacing the condensor with a new style (cross flow) condenser and going back to R-12 I gained 6-8 degrees. Be sure to rebuild the dryer and choose your oil carefully - some are compatible with either and some are not. Don H.

[Randy S.]

Re: C2 A/C

Still can get a vacuum to hold on the system. Now Plan B I am now going to drain the mineral oil from the compressor ( system has not run yet) and AC shop recommends DyEstercool Oil compatible with both. Charge the system with R134a find all the leaks and try it for a while. If not happy once I have a sealed system then I'll spend the big bucks for R12 and 5-10 more degrees.

[Joe Kemp]

Re: C2 A/C

Sometimes I feel you may have to shop around for an A/C shop that REALLY knows GM products and Corvettes. We're lucky here in Tampa to have a shop that really knows thier way around vintage A/C cars (Classic Auto Air).
My 66 BB is converted to 134, and it blows as cold as any R12 Corvette I've riden in.

[Randy S.]

Re: C2 A/C

John,
I am now in the same "warm" boat as you. Since my last post to you, I had the system charged with R134a and I am not happy with the results, about 54F on the standard perf test. I have all rebuilt components and a new codenser and I was expecting temps in the mid 40's. Let me know what you find out?