2000 jeep cherokee sport, 4.0.

Im in florida and its starting to warm up a bit. So I've been trouble shooting my AC problem of it not being cold. Found out the compressor wasn't even turning on. Did some searching and discovered the pressure switch bypass to make it turn on. And bam, it turned on. So I'm thinking all I need to do is add freon correct? The jeep is 2 months new to me so i hope there are no Freon leaks.

I've read that the compressor needs to be running to add freon. So do I have to do the bypass while filling with freon or will the compressor kick on once I start filling it?

 

Hey I'm new here but ill try to help I know some about a/c systems. When I got my 2000 Cherokee this fall I had to add Freon because when I put it on it would short cycle just keep kicking on and off which was the low pressure switch telling the compressor not to run. So if you have a leak or you low on charge below a set parameter I'm pretty sure the low pressure switch will keep short cycling your compressor until you start adding Freon. As soon as the pressure comes up your compressor should stay on. You want at least a 65* air temp outside to get a good charge on your a/c. Charge it with a/c on full blast. Do you hear any sounds or clicking when you turn the a/c on?

 

No clicking that stood out to me. I only turned the compressor on for a couple seconds to see if the compressor would turn on as I didn't want to burn up seals by compressing nothing

 

Firstly, make sure you get r134a refrigerant and NOT Freon. I actually don't think you can even get Freon these days because it requires a special HVAC license to obtain.

Secondly, check your pressure. If the compressor is cycling on and off, then odds are it's hitting the low pressure switch, and you may be able to get away with simply adding refrigerant. If there is really low refrigerant, however, odds are it is just a temporary fix, because that probably means there is a leak somewhere in the system.

If it is a leak, use a UV Dye additive (Available at your local parts store) when you add refrigerant and that can identify where the leak is. If there is no apparent leak in the engine compartment, it's most likely your evaporator core, which are notoriously crappy on the XJs. These are a tremendous pain in the *** to replace, but can be done solo in a few hours.

 

OK Sounds like your just low on freon and the low pressure is keeping the compressor from running since you already jumped your compressor out and know that's not the issue. I would go ahead and add freon to the system and using a can with dye in it can be useful that way if there is a leak in your system you'll be able to use a UV light to locate it. Only other things i would try is test your relay and low pressure switch but easiest solution is just add freon and see where you're at. Let me know I use to do residential ac so i'll try to help as much as I can. I'll go look at my schematics for my XJ and see what i see . I have an issue where my electric fan is not kicking on. I've been trouble shooting it for weeks and not sure yet what component is keeping it from kicking on so it's always trial and error.

 

Yes 134a I have an old habit of saying freon but correct it's 134a. He said compressor will not kick on at all so it's not short cycling.

 

Thanks for the replys. I'll add the refrigerant tomorrow and see what happens.

Doesn't the compressor need to be running to add refrigerant? Will it kick on once I start adding refrigerant or do I need to do the pressure switch bypass while filling it?

 

The best tool you have is to educate and know how the system works.Check this site,scroll to the bottom of the page,they have some good info.
http://www.autoacrepairs.com/index.html

 

It will kick in automatically. Purchase the refrigerant kit with the pressure indicator on it and follow the instructions. Pretty simple.

 

Be very careful adding. The A/C system only takes 20oz, which is NOT A LOT.
Overfilling can cause non-cooling as well, leading you to believe that it's still low. I've learned that there is a fine line with this A/C system; unlike my Ford Ranger (still r12) and my F150 (r134a), which have a broad pressure range to function. This system has be very close to spot on to cool properly, I think in part to the moderately adequate engine cooling and air flow, and lack of insulation for the cabin.

I refilled mine when it stopped cooling last year, I have a manifold and vaccuum pump, so I can do my own work. I recharged it with a 20oz A/C Pro canister from Autozone, and it gets to 52* on Max on warm (90*+) days. Acceptable for me. Before you would be lucky to get 65* wide open.

 

X2

 

Refrigerant does not get old and wear out or lose pressure all by itself, you have a major leak somewhere. Save yourself alot of time, money, & agravation, take it to a shop for an estimate first. You may find it's much less expensive to roll down the windows, evidently the previous owner did.

 

Check for oily spots around the hoses and compressor. Even look around any
insulation covering the hoses. My 99 GC was leaking from under the insulation.
Pulled the hose and had a new hose made for it.

 

I was told by refrigerant distributor at the tires plus were I used to work that you lose 5% of your refrigerant every year into the air lol. I forget what his reason was.All a/c systems after a few years need to be recharged and residential a/c systems usually get charged every year or two and I think that's just preventive maintenance. I worked for an HVAC company for 5 years so I know systems need to be recharged and I know acid can build up in the system as the compressor oil deteriorates and destroy the compressor just don't know specifics because I was more on the heating side and oil burner side.

 

R134 is a very small molecule. A tiny microscopic leak will eventually decompress the system over time. I don't think recharging every couple years is a problem. Now if you recharge it and a week later its warm and the compressor is kicking on every two seconds, then yes you've got a leak.