My compressor has been leaking since the day I bought the car 9 years ago. I've heard that the R4 compressors were known for having these "O" ring leaks from day 1 so GM even created a shield to prevent the oil from spraying on the hood insulator.

I've charged my system with R12 twice, with the 1st time being in 2002 and the last time was in 2007. I've recently noticed my compressor belt flopping around and a moaning coming from the compressor when on. I was told that the compressor needed replacement. The local AC Delco supplier is also an engine/race car builder and knows a lot of people. He made a few calls and located an AC guy willing to rebuild my compressor while trying to keep the original decals and finish in place. It turns out the AC guy is a Camaro guy and wants to help me keep my car original. He will also warranty the compressor. I will be replacing the evaporator and having the entire system flushed.

My question....Will a complete AC rebuild, including orifice tube and evaporator be sufficient for "COLD" AC if running R134a? I've read posts where the 134a isn't as efficient and not as cold. Is that because the system was converted without a complete rebuild? Will my stock sized rebuilt compressor and stock sized evaporator be enough with 134a? Or should I pay extra to have R12 put back in? Any advice is appreciated.

 

i have run r134a in my 89 rs and it was cold. that was with a leaking compressor and just charging it without replacing the accumulator or orifce tube.

 

What state do you live in? Makes a huge difference.
Do you have a certain duct temp you're aiming for?
Would you be happy with warmer than R-12 temps?

I don't see the point in keeping the original decals on the compressor if you go R-134a. You'll need to cover them up with an R-134a sticker as well as switch to R-134a service ports and caps.

 

Pay the little extra it takes to get R12 back into your system. R134a SUCKS, even in brand new vehicles.

 

State = FL
I don't have a duct temp I'm looking for, but I want the system to be equal to original. As we all know, these cars are a huge greenhouse and living in the south, it can be warm when the sun shines. That's why the louvers are staying on the car! I usually drive with the windows down and tops off, but there are occasions when I travel or may get stuck in a rain storm that I need cool temps because of mid 90* temps with the windows up.

The point to keeping the original sticker is because the compressor is an original Harrison built system. My car is a show car and trying to maintain the original look is not an easy task. I could buy a new R4 compressor, but it won't look the same as original. If converting to 134a, I won't need to cover the sticker or replace the service port caps. I can remove the 134a caps and put the R12 caps on and give the visual appearance of original.

If you don't have an all original car, you wouldn't understand the desire to keep it looking original at this point.

 

Don't let Kevin91Z see that you're not doing the EPA service ports and caps. Federal EPA offense and all.....

R-12 service ports are threaded as your car is now. R-134a service ports have a pop on/pop off snap on type setup. I suppose you could keep the old R-12 ports and caps on there if you wanted.

You have leather if memory serves me correct. Even hotter in the summer. I don't think you'll be happy with R-134a in Florida. Our cars don't have much in the way of insulation. So it's up to good air conditioning and good window tint if you want to stay cool. I've got the black leather, black carpet, black car, solid roof deal going here in Texas. Our cars need all the help they can get. I don't know if you consider tint to be an issue with "non original." If you have no problems with tint, I'd recommend a ceramic tint like Formula One's "Pinnacle" tint. Very classy looking and it's high performance, non conductive, and doesn't affect radiowaves (radar, GPS, cell phone) like a metal tint would. Very low reflectivity.

Since it's not your daily driver, the issue of air conditioning isn't such a huge issue. R-134a will cool you so it's not miserable (no A/C). But it won't get you comfortable, cold, or dry. Now since you're getting the compressor fixed, new seals, and changing out the evaporator, it sounds like you might as well put R-12 in and it should last in the long run. A car like yours should last quite a long time with everything running right. You're not wearing out the compressor from having the A/C on everyday all year. You don't have cold weather leaking the refrigerant out or a complete lack of use either (gotta run that A/C once in awhile)

I don't know what you paid for R-12 in the past. But at refrigerantsales.com it's $29/can. Car takes exactly 3 cans (2.25lbs is what my sticker says). You may be able to find some on Ebay for cheaper or find somebody local who has some.

Now if you really want cold. As in OMG this is amazing cold, you could go for Autofrost (R-406a). Works perfectly in R-12 systems. Great oil return. And uses the same mineral oil as R-12. Cools you but more importantly dehumidifies the air better than anything out there. Downside is that if you have a leaky system, it's questionable about topping it vs going for an evac and refill (since it's a blend). But assuming your system is put back together and leak tested, that shouldn't be a problem. $15/can. Takes exactly 3 cans.

Vent temps will run approximately
R-134a: 45-50°
R-12: 40°
R-406a: 30°
The above are in best conditions (moving in city or highway). In stopped city traffic you might add 5-7° to each of those.

In our cars I can say that 40° is nice. No problems with 40°. Once you get into the upper 30's it's utterly relaxing. And low 30's is paradise. An absolute joy on a hot muggy day (aka April-October in FL & TX). With the system running in the low 30's you can expect to see a continuous unbroken stream of water dripping out of the evaporator after you park the car. Depends on outside humidity. Muggier days = more water dripping.

Ultimately I see no point in going R-134a in your car.

 

My only thought for going R134 is the cost of the R12 now and in the future. Are you saying that I won't lose the R12 after a compressor rebuild if done correctly? I thought the defrost or AC needed to be run weekly for the seals to remain in good condition. Unfortunately, my car may sit for weeks at a time. If I do put the R12 back in, then I won't replace the orifice tube or the evaporator. I'll just get a complete flush of the system, leak test and fill with the R12.

How does a compressor get rebuilt? If the sticker is on a solid surface, why is everyone teling me how tough it may be to salvage the sticker on it? Does it get split open with a torch or some destructive method that requires paint? I really have no idea what is involved.

Also, I had no idea that it was against the law to run R12 fittings on a R134 system. I thought it was for the identification of the system on daily use type vehicles that may end up on a used car lot so that any system repairs are done correctly. It makes sense though.

 

Weekly use needed? Oh heck no! A lot of us Canadians only drive our cars in the summertime and park them from Sept-Apr the rest of the year. Most of us still have the original R-12 in the car. There is no leak found. But the systems will be slightly low on a charge. Say 2.0 lbs in a 2.25 lb system. For Canada, the performance is still good enough that no fix is needed.

I moved to Texas and wanted a COLD car. So I went the Autofrost route.

For your car in Florida, you don't have to worry about the tiny amounts leaking due to cold weather over the years. Now the person who doesn't use their air conditioner ever (the stored car that sits in one spot for 5 years) may have an issue with the seals going. But even then it's hit or miss. A friend of mine had R-12 in a Vette that he didn't drive for 12 years. It needed a recharge.
On the other hand, my parents have an 89 Corvette with 8,000 miles on it and the A/C still works like new. Friend of mine has an 88 Z51 Vette. Original R-12 in it. Never been touched. Both have no issues with air conditioning.

The service port issue is understood by you. Meant as a way to identify what is inside people's cars. That way you don't get shops evacuating R-12 into their R-134a tanks or evacuating R-134a into R-12 tanks. (Most shops will have a refrigerant identifier to prevent this anyways)

Now I disagree with the EPA's idea that the service ports be permanently attached to the vehicle. Because once you do that, you can't easily change out to something else. I honestly have never heard of anybody getting arrested for having the wrong service ports and caps on there. Sort of like using an adjustable fuel pressure regulator (they're for off road use only....whatever). There is also the issue of on an R-134a converted car, do you simply screw the adapter on top of the R-12 port? Or do you take the R-12 port off and put the R-134a port there? If you simply screwed it on there (and didn't use a sealing glue which the EPA wants you to do) than yeah, you could simply unscrew it for car shows. But if you took the old port off and put the new one on, you wouldn't be able to remove it without losing all the refrigerant and letting air into the system.

R-12 in general doesn't leak out as often as R-134a does. There are 40 year old fridges that are still on their original R-12 charge.

R-12 has lots of benefits besides colder temperature. There is the lower chance of leakage just mentioned. It's a more efficient cooling refrigerant. It runs with lower (high side) system pressure than R-134a cars have. There is the fact that it runs in mineral oil which is both a great lubricating oil and it's about 100 to 1000 times less sensitive to moisture than the POE or PAG oils used in R-134a cars. Sticking with R-12, you don't have any of the contamination issues with old R-12 oil being in a converted 134a system. Trying to get the R-12 chlorine out of the compressor is hard to do when you convert to R-134a (hence why many recommend replacing the compressor when converting just to save the hassle of the old compressor failing with the incompatible oils after the conversion has been done. May not happen this year. But it might next year.) R-12 also has a higher critical temperature than R-134a. When the critical temperature is reached, it can't change from gas to liquid and liquid to gas anymore. At that point you have no cooling happening. R-12 has a critical temp around 235° while R-134a is around 215°. A hot condenser next to a hot radiator during a Florida heatwave could hit 215°.

 

This would be easier and cheaper if you had a 1LE.

 

Just a note for what it's worth. I converted to 134 here in Kansas. On a 95 degree day, I wasn't sweating, but it was darned close. I went back to 12 when I swapped in a serp system. Now, the fun part. After the serp swap, I had the system charged at shop 1. Within a month, I'd lost it. Had the system checked at shop 2 (bad part) and recharged. All through last summer the air blew cold. A couple of days ago, I turned the AC on and was rewarded with hot air. Back to shop 2 yesterday. Long story short, the techs could find nothing wrong and suggested that, since I hadn't used the system in months, the charge had leaked. They had no other explanation. And I was told to run the system frequently, even in the winter, to keep the seals in shape.

JamesC

 

James, that sucks! A/C troubles are a pain in southern climates is all I can say.

My wife's Blazer sat on the dealer lot for an entire year before she bought it new. It's 8 years old now. Nothing has been done to it. Sounds like the shop was giving you a slightly BS answer. Although there is a minor bit of truth in it.

 

I understand. The system in the Jeep I purchased new in 94 has never been charged or switched on in the winter, and it still blows darned cold.

JamesC

 

Scott:
If "originality" is a high objective, stick with the R12:
it keeps your service ports intact, and runs colder.
I personally would consider a new drier, and orifice or
expansion valve (don't know which you're system has...)
as good insurance. And before final assembly, flush the
entire system -- there's a special cleaning freon for this.
And if the AutoFrost is interchangable into R12 systems,
theres no reason NOT to go that route -- cheaper & colder!!

Reid:
You made a believer out of me w/ the AutoFrost argument.
My question now is how compatible is it w/ the R134 configured
system on my 90 Formula? It's a total resto, so AC components
will be replaced as needed. Can I use the same style of
access ports (i.e. my existing hoses...) & compressor, or is
something more exotic needed?
Hope you'll come out to the Houston meet in July, would like to
meet you.

 

Better news.

I've had crummy luck with R-134a. I had a 94 Z28 that had the A/C fixed twice at the dealer. 1 year later. Nothing. I only drove it in Canada, so A/C wasn't the be all end all. But on those rare heatwave days, it was nice to have.

As far as Scott's car goes, I agree on a new accumulator. And possibly a new orifice tube. If a compressor dies, it will put metal shavings and black goop into the system. This tends to collect in the accumulator (where everything is stored most of the time) and in the orifice tube (which has a screen filter on it) The evaporator tends to be OK as it's easy to flush out the bad stuff if need be.....On the other hand, his car is so low miles, that I doubt he has any real issues with gunk in the system. Sounds like the compressor is probably on the way out. But not dead. So he may get by with just getting it fixed and new seals and an R-12 charge.

As for the Autofrost, well let me tell you. Today I was out on 59 south, going about 30 mph on the highway. (traffic, not because I'm a slow driver. ) The digital temp sign on the side of the highway read 96°. Humidity? It's Houston. What can I say....I managed to get the duct temps down to 31°. Felt wonderful. I wish my home was this comfy. Granted, the temps would rise up once I got stopped in traffic. Running A/C this cold puts a tremendous amount of heat in the condenser and thus radiator. Coolant guage was pinned on 200° the whole time. (I'm running 50/50 right now. Really should add some waterwetter).....I parked the car for 5 minutes and it looked like somebody had spilled a gallon jug of water underneath the car. When I stopped and shut off the car and got out, I was greeted with a wave of intense heat. With the windows up and the air conditioning blowing freezing air on you, you tend to forget how hot it really is outside.

Now converting a '90 Formula to it from R-134a? It's essentially the same as converting back to R-12. New accumulator. Flush the system. New compressor or else taking the current one out out and manually turn the compressor about 40 times while dribbling mineral oil into it to get as much of the PAG or POE oil out. Fill the system with the proper amount of mineral oil. Vacuum and test for leaks. Install Autofrost. The instructions for Autofrost are precise and need to be followed (injected as a liquid, 80% of the R-12 amount, let it stabilize and work it's way through before putting the final can in etc). If you changed the low pressure cycling switch psi to something different for R-134a, you may want to change it for R-406a. But if you have a cycling compressor you're probably OK with that anyways. Mine is set for 26 psi (never adjusted, came from factory like that)

I like to use separate manifold gauges and hoses for different refrigerants just to keep them "pure." No mixing inside the hoses/gauges etc. Now as far as vehicle hoses go, they recommend barrier hoses with Autofrost. But our cars already have them as far as I know.

Service ports & Autofrost: You can use the stock R-12 ports or you can add on the unique Autofrost port adaptors. The adaptors have a same size R-12 port on them. Basically like adding a coloured R-12 port on top of a stock R-12 port. I've never really thought about putting it in an R-134a port.

The same people that make Autofrost make Cool Top. Cool Top is their version of it for R-134a cars. Uses the same oil as R-134a. No special adaptors are needed as it's environmentally clean. I haven't personally used it, so I can't give it a thumbs up or thumbs down. They claim 10° colder duct temps than R-134a.

Lastly, the Houston July meet....I'm a probably maybe. Not sure what my schedule is going to be. I may not have the coolest car. But I will have the coldest car.

 

I WOULD NOT try to have that R4 compressor rebuilt, regardless if it is original or not. They have parts that tend to wear heavily that CANNOT be replaced. Just get a NEW R4 and be done with it. I understand trying to keep it original, but its a terrible compressor to try to rebuild and have a successful rebuild.

 

.

 

The car has 15k miles on it and in the last 8700 miles, probably 2500 were with the use of AC. The car is a Minnesota car and probably has less than 4000 miles of AC use. What parts would wear heavily in that time that can't be replaced? Especially if most on these forums are driving much higher mileage cars with the original compressor still in place. Why do people say the compressor can't be rebuilt? I want the AC to work great and last a while. I think the only reason it's bad now is the oil has been blasting out of it since day one. I also run the AC when I don't need to because I was told by the AC guys that fixed it last time that the seals will dry if I don't run it at least monthly.

 

its your car, so I say rebuild it if you want. I would think the AC guy rebuilding it would know if it could be done or not

 

I don't feel like reading all night, & sorry if someone brought this up already. I may even be wrong all together, but if a compressor is prone to leaking, new, rebuilt, or leaking already. Wouldn't it it be better to add r134a due to the lower PSI? I take hvac classes, but not automotive ac. Seems like in the last 10 months of study, I had ran into information regarding the r12, & 134a PSI. Anyone else know for sure? If this is a repost; sorry. Thought it should be brought up.

 

On the low side pressure, R-12 and R-134a are close for any given temperature. R-134a will have lower low side pressure than R-12 would at the same temperature (which is why you typically have to lower the low pressure cycling switch to get good performance). An example would be

40°F = 37 psi (12).....34 psi (134a)
35°F = 32 psi (12).....30 psi (134a)
30°F = 28 psi (12).....26 psi (134a)

So using the above numbers, it means your low pressure cycling switch needs to be lowered with R-134a in order to get the same maximum cooling point as R-12. Adjusting it from say 26 psi down to 22 psi. This works fine for moderately warm dry weather. But on heat wave days and/or humid climates, it's hard to get down to 22 psi no matter how long it runs.

On the high side pressure, R-134a is much higher than R-12 for a same temperature.

120°F = 157 psi (12).....171 psi (134a)
140°F = 206 psi (12).....229 psi (134a)

So overall, R-134a gives less cooling performance at a given psi and runs higher pressure to shed the heat. This is why new cars tend to come with much larger condensers than old R-12 cars of 20 years ago. Coincidentally why converting third gens with small condensers to R-134a doesn't work all that well.