A/C Question, R134a Conversion

[FWC]

I've done research on the A/C system and I would like to retrofit to R134a.
I understand that the accumulator/dryer would need to be replaced due to the incompatible dessicant, and I would also like to replace the orifice tube.
There are guides for doing this like the one located here, but I have some questions:

1) Where can I get a 134a compatible accumulator/dryer? How would I know if an OEM replacement dryer would be compatible?
2) Can I drain the oil from the compressor without removing it from the engine bay? If not, is it strictly necessary to remove the oil?
3) Besides the dryer/accumulator and the orifice tube, are there any other parts that are necessary to replace?

 

[John Larkin]

I just bought a new accumulator from RockAuto that was designated for the car. It has worked fine.
I drained the oil from the compressor by removing the line from the rear and rotating the compressor and let it dribble out. You do need to flush the lines and condensor and evaporator as much as possible with the flush kit. I think I bought two of those aerosol cans with the hose. Its not too bad, smells funny like citrus.
I used the red orifice tube designated for a 1985 F150 V8 but some are saying the white one is the way to go. Not sure how to source that.

 

[FWC]

I just bought a new accumulator from RockAuto that was designated for the car. It has worked fine.
I drained the oil from the compressor by removing the line from the rear and rotating the compressor and let it dribble out. You do need to flush the lines and condensor and evaporator as much as possible with the flush kit. I think I bought two of those aerosol cans with the hose. Its not too bad, smells funny like citrus.
I used the red orifice tube designated for a 1985 F150 V8 but some are saying the white one is the way to go. Not sure how to source that.

Nice! Good to hear it can be done without removing the compressor. Any particular advice on the flush kit?

 

[John Larkin]

I think it was this stuff. The hose and nozzle look like I remember them. Removing the compressor is not that bad, one tough bolt on the back, got to remove the alternator too. Be sure to see what O-rings you need because you should replace them as they are super old.

 

[wheelstands]

I had my conversion done by an old , trusted mechanic that had converted hundreds of cars in the last 30 years. I don't think the Regal is different than any other air conditioning of the time and he never had any issues or complaints. He simply pulled a vacuum on my system and then added the r134A to about 35 lbs. No lubricant added and no lubricant drained. No parts replaced. It has worked with no problems. I'm sure a lot of air conditioning shops would love to sell you parts and labor or at least make you think it is difficult to do and maybe I just got lucky and my system was in good shape to begin with. I know there would be a lot of controversy with doing it this way and I wouldn't recommend this procedure for anyone else, I'm just sharing my experience. It could all blow up tomorrow!

 

[X Ray]

I used this for my 134 conversion.....works great....A/C Orifice Tube Front 4 Seasons 38635 ebay

 

[Turbo6inKY]

Don't bother with the flush kit. They suck. The flush fluid doesn't evaporate, so when you pull a vacuum, that crap just sits in the system. Use lacquer thinner and compressed air. When you pull vacuum on it, the lacquer thinner will completely evaporate away.

You'll never get all the oil out, so you need to use an ester oil that's compatible with the mineral oil left over from the R12 charge.

You should have an adjustable low pressure switch on the reciever/dryer. There should be an adjusting screw in between the terminals on it. Once you get it charged enough that the system operates without a jumper in the low side plug, you'll need to adjust the low side pressure switch so it cuts off at ~20psi on the low side. They all come set for R12, which is ~25psi. If your switch doesn't have the adjustment, get a new one.

The white orifice tube you can get for $3 from RockAuto works fine.

 

[FWC]

Don't bother with the flush kit. They suck. The flush fluid doesn't evaporate, so when you pull a vacuum, that crap just sits in the system. Use lacquer thinner and compressed air. When you pull vacuum on it, the lacquer thinner will completely evaporate away.

You'll never get all the oil out, so you need to use an ester oil that's compatible with the mineral oil left over from the R12 charge.

You should have an adjustable low pressure switch on the reciever/dryer. There should be an adjusting screw in between the terminals on it. Once you get it charged enough that the system operates without a jumper in the low side plug, you'll need to adjust the low side pressure switch so it cuts off at ~20psi on the low side. They all come set for R12, which is ~25psi. If your switch doesn't have the adjustment, get a new one.

The white orifice tube you can get for $3 from RockAuto works fine.

This is great input, especially about the flush kit and pressure switch. One question is: does the mineral oil conflict with the 134a or with the PAG oil? I'm still trying to understand that. Anyway, I have heard that the ester oil is the way to go, so I was thinking I'd use that.

 

[wheelstands]

I'm curious, can anyone explain why the need to adjust the low-pressure switch? Doesn't it just tell the system that it has enough freon pressure to allow the compressor to turn on? What was the stock switch pressure setting?

 

[wheelstands]

My system is set to run at 35 lps. so I'm not sure how setting the low pressure switch to 20 or 25 lbs would matter.

 

[ITSAV6]

My 91 GT blows 38 degrees. Didn’t even vacuum it down. Added the right oil and 134 and adjusted low switch I have to add a little ever summer. 218,000 miles on all factory components

 

[Turbo6inKY]

This is great input, especially about the flush kit and pressure switch. One question is: does the mineral oil conflict with the 134a or with the PAG oil? I'm still trying to understand that. Anyway, I have heard that the ester oil is the way to go, so I was thinking I'd use that.

The mineral oil isn't approved for use with R134a.
Ester and PAG are. But mineral oil and PAG don't get along in the system. It creates a nasty goop that clogs up the orifice tube and the condenser. Ester will mix with mineral oil and not react with it.

 

[N2BUICK]

I'm curious, can anyone explain why the need to adjust the low-pressure switch? Doesn't it just tell the system that it has enough freon pressure to allow the compressor to turn on? What was the stock switch pressure setting?

The low pressure switch is a compressor cycling switch. It should be set to a cut out point that will prevent ice to form on the indoor evaporator coil. For R134A, 30lbs pressure equals 35 degrees. There are many variables, compressor speed, OD temps, humidity. We are changing to a refrigerant that these cars were never designed for, is a big one.
Surprisingly many cars are converted and seem to work well. I am surprised there is no mention of changing the condenser coil?

 

[Chuck Leeper]

I am surprised there is no mention of changing the condenser coil?

I do. Change to the multi-pass unit.
Last one was $120 from NAPA.
Original units have been subjected to dirt, bugs repeated heat cycles and are on the downward side of the capacity to reject heat.

 

[N2BUICK]

Yes, condenser change is a priority.
Guys who live in the north my not need the extra heat rejection, that a new design of condenser coil can give.
Guys in the hot areas will need it, especially in stop and go traffic or long stop lights.

 

[John Larkin]

I looked up multipass condenser on internet, not much there, found one for a Mopar.

 

[Chuck Leeper]

https://www.napaonline.com/en/p/RNRNC4013A?impressionRank=8

A NAPA part. Parallel flow.
Of course, out of stock at my local, "never in stock" store.
No longer $120 either. My price would be close to 150-160.

 

[John Larkin]

Its out of stock everywhere.

 

[TurboTGuy]

There are 134a pressure switches for our cars available out there, I have an extra one hanging around somewhere, but I cant find it.

They are also denoted as 134a between the prongs on the connectors that plug in.

 

[hensleyt]

I have a need for the switch and condenser too

Yes, condenser change is a priority.
Guys who live in the north my not need the extra heat rejection, that a new design of condenser coil can give.
Guys in the hot areas will need it, especially in stop and go traffic or long stop lights.

AC worked OK in Hawaii but returned to AZ and I thought it was low on gas, just checked today its a little low but only blowing 70 degrees but its not that low.
no condenser in a 50 mile radius of me in Az and have no clue about the switch part number other than Highway Stars