Switching AC to R134

[custodian]

I have an 86 C30 with the 454 that has AC. I want to switch it over to the newer R134 refrigerant. I'll be pumping it down to see if it will hold a vacuum. I want to use the compressor that is on it. What all is needed for the switch?

 

[Sad Sack]

With my '85 I did new compressor, accumulator/drier and orifice tube. Didn't do condenser and end result was good cold air. Some will recommend a new condenser; I rolled the dice and got a seven. Had a friend that is good with A/C help and had the gauges. Only issue was the manifold O-Rings, had to hunt some down that fit.

Update: Forgot to add the adapter kit required.

 

[Bextreme04]

pull all the individual sections apart and replace all o-rings with the green ones. You can get a whole mixed size box of them from any parts store and there aren't that many connections. I did that, replaced the accumulator/drier, blue orifice tube, rebuilt the A6 compressor, and flushed the condenser and evaporator. Re-filled the compressor and individual parts with PAG 120 and then charged with R134. It will freeze you out of the cab in the summer it blows so cold.

 

[fast 99]

refill 80% of R12 charge with 134a. In other word is it requires 3 lbs of R12 use 2.4 lbs 134a.

 

[Finkaire]

To retrofit an R12 to R134a AC system, you must first recover the R12, then replace the R134a service port adapters and the filter drier. Next, flush the system to remove incompatible mineral oil and fill it with the correct amount of ester oil. Finally, evacuate the system to a vacuum, charge it with R134a to about 85% of the original R12 charge, and attach the new service port caps and warning label.
Ps: It is not possible to flush the compressor, drain and refill. For that matter, I am not sure that flushing would be required. Replace the accumulator and the orifice tube, careful removing the orifice tube, don’t break it. Leave it in if you think you going to break it. My 2 cents

 

[Rickf]

All good advice. When I converted from R12, I replaced everything a/c related under the hood, bought a kit and followed the instructions.

 

[Hunter79764]

Good advice above. On the condenser, if you have a single cab, you're fine. If your C30 is a double cab and you want it nice, you might want to upgrade to a modern style parallel flow. If you have a decently cool climate, stock is fine. On Suburbans, I'd recommend the modern style for sure, especially with rear air. Airflow up front will be more critical with 134, so if you spend a lot of time idling with AC on, think about either electric fans or making sure your clutch fan is working as intended/upgrade to an HD unit.

 

[YakkoWarner]

My Suburban never got comfortable with the original system running 134, it had been messed with before my purchase and I expect all they did was refill it with 134 and hope. My intent is to use the earnings from next spring's seasonal job to do a major rework (A6 compressor instead of tired R4, parallel-flow condensor, new dryer/accumulator and orifice tube, green O rings, etc).

Almos everyone recommends flushing the remaining lines and system which sounds like a great idea, but no one ever mentions what they should be flushed with or how.

 

[Bextreme04]

Almos everyone recommends flushing the remaining lines and system which sounds like a great idea, but no one ever mentions what they should be flushed with or how.

AC system flush fluid and the rental flushing tool from your local autozone would be my vote. For the big stuff like the condensor and evaporator, I would fill with mineral spirits and swish it all around first, then use the AC flush. You are having to disassemble the whole thing to put new o-rings and orifice tube anyways, just flush all the parts individually that you are going to re-install, then assemble with new parts and the appropriate PAG for your compressor. I rebuilt my compressor when I did my conversion using new seals rated for the R134.

 

[edgephoto]

I have done dozens of conversions back in the 90s. The proper way is to replace orifice tube, accumulator and drain all oil out of each component and measure what was removed. Then replace the hoses with new barrier hoses, all o-rings replace and put a compatible oil back in the amounts you removed and charge to 80-85% of the R12 charge amount.

In reality, nobody wanted to pay for this. What typically happened was the leak was repaired or the compressor was replaced and compatible oil was put in and the system charged to 80-85%. I never had anyone come back complaining of the A/C not being cold enough. These old systems were huge and had way more capacity than they needed. So losing a fraction of the capacity was not noticed. Maybe the compressor ran longer before it cycled off?

I am currently restoring my 1987 V3500. Since it was torn down to nothing I replaced everything in the A/C system. Getting close to firing her back up.

 

[Hunter79764]

These old systems were huge and had way more capacity than they needed. So losing a fraction of the capacity was not noticed. Maybe the compressor ran longer before it cycled off?

I think it depends on the vehicle. 80's Monte Carlo's are marginal with the R12 system, and a cheap swap to 134 means almost no one is happy. Upgrading the condenser puts it back to factory levels of "almost cold enough", and electric fans usually makes it a viable modern system. Single cab trucks are way overkill from the factory, but the SUV's put a lot more load on the condenser, especially with rear air, and it needs some help.

Fun fact, auto AC systems are generally in the ~5 ton capacity range, sometimes more. It seems like a lot when a house may have half of that, but a house is only maintaining that temperature, a car needs to get from 125° interior down to 70° in 5 minutes, or else Momma ain't happy... It does it by being HORRIBLY inefficient, but for a car, an extra 2 or 3 HP makes very little difference to fuel costs compared to a home AC that runs hundreds or thousands of hours a year.

 

[fast 99]

I have done dozens of conversions back in the 90s. The proper way is to replace orifice tube, accumulator and drain all oil out of each component and measure what was removed. Then replace the hoses with new barrier hoses, all o-rings replace and put a compatible oil back in the amounts you removed and charge to 80-85% of the R12 charge amount.

In reality, nobody wanted to pay for this. What typically happened was the leak was repaired or the compressor was replaced and compatible oil was put in and the system charged to 80-85%. I never had anyone come back complaining of the A/C not being cold enough. These old systems were huge and had way more capacity than they needed. So losing a fraction of the capacity was not noticed. Maybe the compressor ran longer before it cycled off?

I am currently restoring my 1987 V3500. Since it was torn down to nothing I replaced everything in the A/C system. Getting close to firing her back up.

Yes, its very hard for customers to justify replacing most of the system. We cut corners trying to keep the costs down. Generally it was a new drier, compatible expansion valve, unhook the compressor flush out as much oil as we could, replace oil, recharge. In some cases was too labor intensive to replace the o rings. For flushing we used flush fluid squirted or poured some in each component and blew it out with compressed air. Might not be the procedure you want to used for a vehicle retained for a long time, however it doesn't need to be over complicated either.

 

[edgephoto]

Yes, its very hard for customers to justify replacing most of the system. We cut corners trying to keep the costs down. Generally it was a new drier, compatible expansion valve, unhook the compressor flush out as much oil as we could, replace oil, recharge. In some cases was too labor intensive to replace the o rings. For flushing we used flush fluid squirted or poured some in each component and blew it out with compressed air. Might not be the procedure you want to used for a vehicle retained for a long time, however it doesn't need to be over complicated either.

If we are restoring something and plan to keep it going for a long time then it is best to do it 100% by the book. My experience has been that there are some corners that can be cut and still get good results. Especially when you are doing it for a living. You have to balance things out so the customer is happy. Labor is the big expense and if you do it yourself you don't have that expense.

@Hunter79764 , I see you are in TX which explains your comment about 80s Monte Carlos. I never owned a Monte Carlo but I owned a 1987 Buick Regal T-Type for years. Had to convert it when the compressor failed. I never noticed a reduction in performance nor did my brother on his 1981 Cutlass. We get some really hot and humid days in the summer but nothing like the temps in TX. I know people in the South and South West put limo tint on their windows to help with interior cooling. Without it the A/C in some modern cars won't keep up.

 

[Hunter79764]

Yeah, Texas heat can be a beating, the UV too.
I think the Monte's have a little less cooling airflow than the other G's, but my thoughts were that the blower was just never enough. After I converted it, my wife would barely ride in it in summer time until I put an electric fan on it, and many others on the Monte forums had similar issues. And then working as an HVAC design engineer, I saw shy the R12 to 134 swap was so hard on a condenser, as well as how much more effective the modern parallel condensers are than single row tube and fin. If it needs a kick in the pants, that is the best way to do it.

 

[fast 99]

If possible convert it over to a more modern compressor such as a Sanden. A6 and R4 compressors can be problematic.