So, before I drop the car off at a mechanic I just wanted to run this buy you guys in hopes that we might have an AC expert on hand.

The car in question is a 2001 Jeep Cherokee with 131k miles.

The issue is the air conditioning. When you start the car up and turn on the AC the compressor clutch very clearly engages and the air starts to blow cold through the vents. After a few minutes at most the cold air goes away and it starts to blow in regular air from the outside (even when the **** is set all the way to cold). Not only that, but once the vehicle is up to operating temperature the AC compressor clutch no longer engages or anything. It seems like the only time the clutch will engage and the system will blow cold air is during the first minute or two upon starting the car in the morning (when the engine has been sitting all night and cooled down).

Any ideas as to what could be the issue?

 

Jumper the low pressure sensor (near the low pressure fill valve). Use a paper clip to bridge the terminals and see if the compressor stays engaged for longer than it did before.

If yes, you have low refrigerant pressure. If no, you have an issue with the compressor. Could be a bad clutch (you can use shims to get more life out of it), could be electrical, etc.

Jumpering the low pressure sensor is the fastest way to test it in any case

 

I will try that, though I'll have to wait until the engine is fully cooled down. I found it odd that the only time the compressor would engage is when the engine has been sitting for hours and fully cooled down. Once the engine has been running and gets up to operating temps the compressor won't engage at all, period.

 

Well, if the low pressure sensor is tripped, the compressor surely won't engage. I would jumper the sender when the motor is warm and just see if the compressor engages.

If it does, and stays running, you might be good to just fill it and go (after making sure there are no leaks).

Let it run for a minute or two and listen for any abnormal grinding, and make sure that the case of the compressor does not get too hot, which could indicate excess friction (bad clutch or bearing)

 

it sounds like you have a restriction in the system and your high side pressure is getting to high. Does your a/c fan kick on when you have the ac on? you really need to get a set of gauges on it to see what is actually happening. most likely issue is the condensor is plugged. take it to a shop and get it checked out. most shops charge 20 dollars to get a set of gauges on there and let you know what's going on

 

Yes, when you turn on the AC the compressor doesn't engage but the fan does indeed turn on. I think my best bet will be to take it to a shop. Even if it is the compressor and I can replace that myself, I still don't have the tools needed to clear out the system and everything.

 

So, it turns out it was the compressor itself. It started getting loud and making a very obvious howling sound. I went to Autozone today and got a new compressor for $196 and installed it this afternoon along with a new orifice line and all new o-rings.

I'm going tomorrow to have the entire system vacuumed out, leak tested, and then recharged by a pro. Should be good to go though with the new compressor and everything!

 

You should also replace the drier while you are at it. Cheap enough

 

Yeah, odd thing is I got a replacement drier from Autozone and for all intensive purposes it matched up 100% look wise but on where the two lines screw into it the inside was slightly different on the replacement drier and while the lines screwed in it seemed to be missing some sort of a 'shoulder' section inside of where the lines screw into. I was worried about putting the new one on because something in my head was telling me it might not seal properly with this new drier.

I need to see if I can find a drier that will actually be 100% OE.

 

My 01 poped the stud on top of the dryer last summer , oreilly had the right dryer .