Having AC issues.

97 4.0 4x4 auto with no other current issues aside from the AC.

So, my AC worked just fine last summer and blew icey cold. This year I used it for the first time recently and it blew warm air. Driving with the AC on for a while it will eventually blow cooler air it seems but I can't find any pattern as to when it blows colder vs. warm. It is never ice cold just cooler than when it blows ambient warm air. Different settings produce the same results and the heater settings work as they should and the fan blows at all the correct speeds. The compressor cycles on/off as I've always remembered it and the Efan kicks on when the AC is on and seems to be working just fine.

I don't have proper gauges(I know that limits my ability to diagnose) but I have the low pressure side that usually comes with the refill cans. With the low pressure gauge hooked up, engine at operating temp, ac set to max the gauge was fluctuating from the very Low end to the slight Alert range on the gauge. I added just a little bit so that it doesn't dip into the low and stays mostly in the Fill range and creeps into the Alert range still. The fluctuation is rather extreme and I don't remember it being that way in the past. I remember always filling it to the Fill range and when the pressure builds/drops it would stay in that same Fill range. Now it seems my pressure is jumping drastically. My level has remained stable and no sign of any leak.

The compressor was replaced with a Spectra back in 2010(apx 40-50k miles ago), with it was a new dryer and fresh (vac)charge of refrigerant. Since then I have had zero issues until now. Every other oil change or so I blow shop air from behind the radiator to try and knock out any debris and keep air flowing.

I am thinking its best to move forward with an exac and recharge but not sure why the refrigerant would just go bad or cause that issue. I think the drastic pressure change is trying to tell me something. I am also leaning towards buying a set of proper gauges to see exactly what is going on but thought I would try to figure it out without them if I can save the money.

Any suggestions would be great.

Gauges are not that expensive and very helpful. The readings will cycle as the compressor engages and disengages. You may have some leaky connections, low charge, and some air in the system or a weak fan clutch. Just a guess. Correct charge is by the weight of the refrigerant added. It can also be done if you have a very good understand of what ambient temperature you have and the correct pressure at that temperature.

I think you have a slow leak. With the jeep running and a/c on see if the clutch engages, freon dont wear out, so somethings up. If it just kicks in and out or not at all, try shooting a little freon in it and see if you get the compressor to kick in. If it kicks in and blows cold after you do this, you have a leak. Could be a valve core at the service port, or a fitting somewhere......you can fill it with nitrogen and check for leaks too....

The ac clutch engages as it should. Fan cluch is a Zj setup and seems fine, no over heating issues and efan comes on and blows as strong as ive remembered it being.

Seems odd if it has a leak but my level still is showing the same on the gauge after about a month now, it hasnt dropped any.

Harbor Freight sells a gauge set. They work fine for me. To me it sounds the compressor is cycling because the pressure does not stay constant. On a hot day it should stay around 30-35 psi. If the freon is low then the compressor will keep pulling the low side pressure down until the low pressure cut off switch shuts off the compressor

DONOT add any more refrigerant until you can see what the system pressure is doing. The gauge manifold will help you diagnose what the system is doing while the compressor clutch is engaging and disengaging...
There is a slight chance the metering orifice is getting partially obstructed causing the low pressure switch to disengage the clutch.

I noticed a small dent on the hardline that runs along the frame near the motor mount. I don't know if its enough damage to be causing my issues or not. Seems like a very minor indentation in the line but I may look into a new hardline and see.

Same level, cold sometimes, sometimes not? Sounds like the compressor clutch to me. Works for a little while, starts to blow warm. Turn it off for a while, and it will work again... for half an hour. Unless you can see the clutch lagging, you won't be able to tell much without looking at the pressure differential on a pair of gauges.

Parts stores loan them out around here, if you don't have them.

Thanks for all the input guys, I think I am going to either take it to an ac shop or invest in the gauges next.

I haven't really had it blow cold air either lately. I think the few times it did blow cold was because it was cold enough outside to make a difference and now that its been just Hot it hasn't blown cold at all.

The clutch cycling does seem to be going to fast, I know it used to cycle but I think it should be staying engaged longer. Something is causing the clutch to disengage.

I just never have luck with AC in vehicles I swear. !!!1

You don't have to buy the gauges, you can borrow them from most parts stores.

Re reading, it sounds like through adding refrigerant, you may have introduced non-condensables to the system. A quick spike could be moisture freezing in the expansion orifice. For what it's worth, if you plan to evacuate and try again, replace the filter/dryer first. Expansion valve is $2 or less.

NOTE*** If you find shavings or gray sludge at the expansion orifice, expect to replace the compressor and everything which can't be flushed, namely the evaporator.

Someone has been saying the dent in the hardline is most likely my issue. I am just not sure if a small dent would be enough to effect the system. I know the orifice tube is in that hardline but I thought it was at the very end of it and not in the middle of the hardline.

iwannadie said:

Someone has been saying the dent in the hardline is most likely my issue. I am just not sure if a small dent would be enough to effect the system. I know the orifice tube is in that hardline but I thought it was at the very end of it and not in the middle of the hardline.

Click to expand...

It's in the middle. The tube has pinches to hold the orifice in place.

Maybe if it gets cold past the dent?

Just to follow up even though it's been forever ha.

I finally decided to deal with the ac(its only supposed to be 120 degrees here).

Replaced the hardline with a new one and new dryer. Pulled a vacuum and recharged and the ac blows like the artic now.

Inspecting the old hardline I dont see pinches where the orifice tube would be. The new line has clear pinches along the same area where mine was dented. Maybe the old line didn't use pinches to hold it in place?

Either way seems the hard line replacement was the cure.