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R-12 to 134A

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I was at the bone yard this morning, and spotted a 96XJ with a newer looking AC System. Would you change from a R-12 to a 134A? How is the cooling with 134A? My 1989 MJ 4.0 has the old R-12 system, After changing the blower motor and looking through the mounting hole, I noticed that the evaporator coil is clogged with dirt and probably cannot be cleaned, so it needs to be replaced, the old lines look questionable. Dryer probably needs to be replaced. There is still pressure on the system, its just lower on R-12. The site glass flashes when you turn on the AC and let it run. It seems to go off on the low pressure control. What would you do? Is it a direct change over if I take all the componets off the 1996 XJ. If you choose to do this job, what would you replace with NEW parts, like maybe the dryer.... what do you think? Will the condenser fit my MJ, will the 134A evaporator coil fit where the R-12 was? Just thinking out loud? What has been your experience? :idea:

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Last summer I had to replace the compressor on my '89, also, my condenser and dryer needed changing, so I changed over to R-134A. The main thing is to flush the system then evacuate it before you charge it with the new freon. Also, since you will already have depressurized the system, go ahead and replace all of the old o-rings to eliminate any leaks. If you need to replace the evaporator, I am pretty sure that you will have to remove the entire dash to get at it. It is a PITA, so, if you think it needs changing, do it now, while the system is depressurized.


On retrofitting the XJ system, they should be the same. Keep in mind that there are two (2) different compressors for our trucks; the clutch is shorter on one of them. I had to go back to NAPA to change out the one that they ordered for me, because it had the wrong clutch, so compare the XJ compressor with yours to make sure it is the same. The other parts should be the same on the XJ and the MJ. Because the evaporator is so hard to replace, I would go with a new one. The other parts are readily accessible, so, if the XJ parts are good, I would use them, except the drier, which I would replace regardless. Just be sure to replace the old o-rings.


I'm sure there are A/C gurus on here, who can chime in and give you much more detailed info.


Good luck and have a Happy New Year,


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I would change over the to the R134 too. Whenever you open the system you should change the reciever/dryer because it gets moisture in it and doesn't work as well. If you are going to change your evaporator core change your heater core while you are in there. The heater core/evap core is about an 8 hour job. You have to drop the steering column or remove it and remove the entire dash. Then you have to remove the inner airbox and split it to get to the cores. Keep track of the doors for switching because when you break the box apart they will fall out. It would be easier to remove the seat(s) so you can drop the column far enough to clear. 134 is just different oil and freon, you just have to get a fitting conversion kit.


Hope this helps

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Thanks for the information Hellcreek and Knever3, I will do it, the Evaporator coil in my truck looks like some heat shink black plastic that had hair, that's how clogged it looks. Have you every seen a home AC evaporator coil with the return air located at floor level which has been run without a filter for a long time. YUK It will make you mad :fs1: It Looks like a DIRT test, to see if the coil can grow anything

Thanks for the tip about the compressor length and the "O" rings replace, and Yes I kind of figured it was going to be a PITA. But If I do it right the first time, with a new heater core, and a new evaporator coil, than it will be a very long time before I will have to do it again.

PS what about the expansion valve, it seems that has to do with that block of aluminum on the firewall where the high side and suction line pass one another.

Is the electrical hook-up the same wire for wire?

You guys give good tips :D


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