1991 Cherokee Limited - A/C Overhaul Questions

Hey guys -

My Jeep is a 91 XJ limited with the 4.0. My AC stopped working about 5 years ago and I never fixed it. I get a quote from a shop every year thinking “now is the time” but the $1200 estimate never sits well and another year goes by. My Jeep has transitioned into being my Fall-spring vehicle but driving my 8.1 Yukon XL in the summer just for AC isn’t sitting well with the gas budget. Anyway, I have been totally oblivious to how to repair my AC until recently when I started reading, and have generated some questions that hopefully won’t make me look like a total idiot.

Hope you guys can help! Once I get working on it I’ll post up progress and questions here too.

The plan:

Buy the kit below, replace the compressor, condenser, drier, expansion valve and MAYBE the hoses in between. Then take it to a shop, get a vacuum pulled on it to test for leaks and charge it. Since my heat works (not that that has anything to do with this) and I haven’t seen any water on the passenger side I am crossing my fingers my evaporator is OK.

https://pitstopauto.com/Catalog/Sin...TxZeqV8XUcFHLIL3QRGZbfwlgMvib_voaAm2UEALw_wcB

My questions that I have generated so far:

1. If my AC hasn’t worked for 5-6 years and I was told I had a leak from my condenser, is it safe to assume I can just start ripping into the system without recapturing anything? Is all the refrigerant gone by now?

2. Do compressors come pre-oiled with the correct amount of oil? Do I need to do anything there besides bolting it up?

3. Do I need to lubricate all these o-rings upon assembly or is dry assembly preferred? I was going to use some light silicone grease like I do with all other o-rings.

4. Assuming I get all this hooked up, it’s safe to drive the Jeep to the shop with the AC off without hurting anything I’m assuming...?

I’m sure I’ll think of more things but thanks for the help!



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1. Yes, your system has long been "evacuated"
2. Not in my experience but it may depend on the compressor
3. I used a bit of PAG oil (the stuff in the compressor) to lubricate them before assembly
4. Yes, the compressor will not turn on until it has some charge in it


These guys will sell you the correct PAG oil (under "Tools & More").

https://jeepair.com/


Since you are not replacing your evaporator you will need to clean the existing one out. It will still have some of the old R12 oil in it which isn't compatible with PAG. Any auto parts store will have some available but be sure to buy the version in a pressurized can so that you can blow it through the evaporator:


https://www.oreillyauto.com/detail/...a-c-system-flush/ca1/4384840?q=ac+flush&pos=3


Note that the expansion valve differs depending on the model year. A '91 will have the R12 expansion valve which has a slightly smaller thread size on one of the orifices but that is the one you will need if you are keeping your existing evaporator.

HTH
Todd

tjmotter said:

1. Yes, your system has long been "evacuated"
2. Not in my experience but it may depend on the compressor
3. I used a bit of PAG oil (the stuff in the compressor) to lubricate them before assembly
4. Yes, the compressor will not turn on until it has some charge in it


These guys will sell you the correct PAG oil (under "Tools & More").

https://jeepair.com/


Since you are not replacing your evaporator you will need to clean the existing one out. It will still have some of the old R12 oil in it which isn't compatible with PAG. Any auto parts store will have some available but be sure to buy the version in a pressurized can so that you can blow it through the evaporator:


https://www.oreillyauto.com/detail/...a-c-system-flush/ca1/4384840?q=ac+flush&pos=3


Note that the expansion valve differs depending on the model year. A '91 will have the R12 expansion valve which has a slightly smaller thread size on one of the orifices but that is the one you will need if you are keeping your existing evaporator.

HTH
Todd

Click to expand...

Todd,

Thanks for the information! Super helpful.

I may just purchase the kit from Jeep Air if that’s the case.

Also I guess a pertinent piece of info was that I did have the system repaired at one point in time beyond 6 years ago (we’ve had the Jeep in the family since 1992) and it was converted to 134A from R12 so the right stuff should be in there. I think your flush idea is a good one anyway and seems like a piece of cake if the expansion valve is off anyway.


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