R12 to R134a conversion - JeepForum.com
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post #1 of 14 Old 08-29-2019, 01:34 PM Thread Starter
Bdavis100200
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R12 to R134a conversion

I am putting AC on my CJ with an AMC 360. I am using the evaporator unit, condenser, dryer, and lines from a YJ. I am using a 360 compressor. What oil do I need and how much? Also how much R134a do I need? I know that you are supposed to use 85% of the factory R12 amount. I am pretty sure that I will have to make adaptors for the lines to work on the compressor. The lines are O-ring and the compressor is flare. Thanks in advance!

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post #2 of 14 Old 08-29-2019, 06:05 PM
Rtracy2001
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The correct oil is a PAG (polyalkylene glycol) oil to be compatible with the 134a refrigerant. The amount of oil and specific viscosity will depend on the compressor and I don't have a good answer for that. What exact model of compressor do you have? York 210, Saden?

If and when you get to the point of charging the system, have a a pro, or someone experienced with AC service help you and fill until the pressures (both high and low side) are in the proper range.

Every 20 minute job is just one broken bolt away from a three day ordeal.
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post #3 of 14 Old 08-30-2019, 08:33 AM Thread Starter
Bdavis100200
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York 210
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post #4 of 14 Old 08-31-2019, 07:25 AM
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Are those used parts or new? I would highly advise not reusing the dryer and install a new part. Also, if they previously had R-12 in them you will need to use an oil that is compatible with both refrigerants. PAG oil will not mix.
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post #5 of 14 Old 08-31-2019, 06:13 PM
Rtracy2001
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Quote:
Originally Posted by OrangeCJ-5 View Post
Are those used parts or new? I would highly advise not reusing the dryer and install a new part. Also, if they previously had R-12 in them you will need to use an oil that is compatible with both refrigerants. PAG oil will not mix.
Agreed, the oils will not mix. The refrigerants themselves don't mind as much. Some folks will even give an R-134 retrofit system a shot of dry (oil-less) R-12 to improve cooling. (Never tried it myself though.)

When I worked in auto parts, compressors were sold without oil and the installer had to add whatever oil they were using and rotate the compressor several revolutions to lubricate the internal parts. Now that R-12 is nearly extinct in the automotive world, many compressors come pre-charged with PAG oil (R-134a being the most common refrigerant in use now). In any case, if a part must be reused, a thorough flush is needed. The only part that contains refrigerant that I would consider reusing would be the compressor itself, and then only in the case of the York 210 style (though I admit, I would be far more likely to convert it into an air compressor than use it in air conditioning). Remember to remove the oil in the reservoir and flush. Most of the rest of the parts are incredibly inexpensive. AC component pricing has dropped significantly in recent years with things like receiver/dryers frequently being found for under $10.

https://www.rockauto.com/en/catalog/...cumulator,6972

Note that the earlier model CJs used the York compressor, you may be able to find the lines to connect directly without adapters.

Every 20 minute job is just one broken bolt away from a three day ordeal.
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post #6 of 14 Old 09-01-2019, 11:19 AM Thread Starter
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Would a reman York 210 compressor already have PAG oil in it? Would I have to add more oil to the system? I have read so many arguments whether or not you should add more oil when replacing a compressor. I have also heard of people using Ester oil. I have a new dryer and serpentine style condenser for a 95 YJ.
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post #7 of 14 Old 09-01-2019, 08:18 PM
Rtracy2001
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Originally Posted by Bdavis100200 View Post
Would a reman York 210 compressor already have PAG oil in it?
That depends on the remanufacturer, some do, some don't.

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Originally Posted by Bdavis100200 View Post
Would I have to add more oil to the system? I have read so many arguments whether or not you should add more oil when replacing a compressor. I have also heard of people using Ester oil. I have a new dryer and serpentine style condenser for a 95 YJ.
starting from a dry system, yes. I recently redid the AC in my truck and the instructions included guidance on the average amount of oil to add for each component replaced in that system. For example, the average receiver-dryer on a Chevy OBS pickup holds about two ounces of oil, same for the condenser, but these numbers will vary by application.

Since most of the system is from a YJ, maybe you should start with the YJ system capacity plus the York reservoir capacity. (Add the proper amount to the reservoir, not the lines.) The purpose of the oil in the system is to lubricate the compressor, the York uses that nice internal reservoir as the primary lubrication and only a little oil circulates.

An easier route may be to get a York to Saden adapter plate and just use the YJ or TJ compressor. Lots of info on those and you may be able to get a compressor designed for 134a, which would solve a lot of performance problems as R-12 and 134a operate at different pressures with 134a requiring higher pressures to cool equal to the R-12 (IIRC).

$0.02, I am not an AC tech, take with a grain of salt and verify through published sources.
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Every 20 minute job is just one broken bolt away from a three day ordeal.
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post #8 of 14 Old 09-04-2019, 05:57 PM
1970pelle
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The biggest issue with A/C conversion is getting the vehicle to cool when sitting still. I'm jumping past a lot of information here to get right to the point.
The reason for poor cooling from a system conversion, is not enough condenser cooling surface. The R12 condensers have smaller cooling tubes inside the condenser, and not near enough to cool the 134A as original 134A condenser has.
So the best fix is find a 134A condenser from another vehicle that will fit the space and have the biggest amount of cooling space in the core support opening. So if your condenser is 12'X12' find another 134A condenser very close if not a bit bigger to replace yours.
Also a cycling switch from a 134A system, a TJ system is very close in size to a CJ it will work. Also use a 134A filter drier/accumulator. If your system is using a accumulator be sure to use a 134A orifice tube or H-valve(expansion valve).
As far as A/C oil, look up the OEM system add the correct amount for the OEM evaporator then the drier if equipt(usually 1oz. all systems) the condenser will come with fill instructions or look it up. Vacuum and fill, according to the A/C gauge readings. There is no set fill level on a converted system. There never the same close, but not close enough.

Ken
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post #9 of 14 Old 09-05-2019, 10:41 PM Thread Starter
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I am using a 95 YJ evaporator so it is for r134a and it almost covers my 4 core radiator. Thanks for the details.
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post #10 of 14 Old 09-06-2019, 06:43 PM
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Quote:
Originally Posted by Bdavis100200 View Post
I am using a 95 YJ evaporator so it is for r134a and it almost covers my 4 core radiator. Thanks for the details.
Condenser is in front of the radiator. The evaporator is in the heater box.
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post #11 of 14 Old 09-07-2019, 08:46 AM
1970pelle
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You are pretty much stuck with having to use the stock Evap coil. I would check and see if a TJ condenser would work in front of your YJ.

Ken

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post #12 of 14 Old 09-08-2019, 07:25 PM Thread Starter
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Quote:
Originally Posted by 1970pelle View Post
You are pretty much stuck with having to use the stock Evap coil. I would check and see if a TJ condenser would work in front of your YJ.

Ken
All of this is going in a CJ.
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post #13 of 14 Old 09-10-2019, 01:51 PM Thread Starter
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Quote:
Originally Posted by OrangeCJ-5 View Post
Condenser is in front of the radiator. The evaporator is in the heater box.
Just noticed I said evaporator. I meant condenser.
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post #14 of 14 Old 09-14-2019, 02:50 PM Thread Starter
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Got the ac done. Held a vacuum and got it charged. Thanks for everyones’ help.
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