00 Cherokee A/C Diag

[140]

Recently purchased a 00 Cherokee Sport, and I'm tried to diagnose A/C issues.
My wife drives it normally, but I have driven it a little and her description seems to be accurate. Start the car (cold start) and the ac will blow semi cold for 5 to 10 minutes, then gradually fade away to outside air temp. I would add to her description that (cold start) the compressor will engage when the car's AC is turned on, and will stay engaged at idle probably at least 10 minutes. If you bring the rpms up to 1100-1200 the compressor will disengage and then re-engage in the same fashion it does normally (only i suspect because of high pressure cut off switch rather than low pressure). Once the car is allow to idle again, as long the system is still not up to operating temps the clutch will resume being engaged with out kicking on and off.

At the time I checked my pressures the outside temp was appx 65 F. My static high and low side pressures were around 70 give or take a few psi, both sides. Started the car and the pressures remained the same as static on both sides. After 5 minutes or so of warm up the pressures began to rise, but remained within 5 psi or so of each other. After 10 minutes the pressures had reached about 90 psi, swinging just over 100 when I raised rpm to 1200. The high side started to creep to a little more pressure than the low side, but no more than 5 to 10 psi differenc. The high side line felt hot to the touch and the low side more towards warm. Compressor stayed engaged the whole time unless the rpms were brought up. The vents blew pretty cold air (no temp gauge yet), way colder than outside air, but not ice cold or anything. I am aware that these readings point to either a worn out compressor, or possibly an expansion valve, but had questions. I noticed after disconnecting the quick release valves to my gauges that the refrigerant residue on the inside of the valves had neon die along with it, so someone has added either die alone (looking for leaks, but I don't see any), or R134a with die added. Is there any way that my system is just over charged? I would think my readings would be high on both sides with a large difference between the two? If my compressor or expansion valve is shot, then why the cold air out of my vents?

Thanks a lot!

[140]

Ok, I'm an idiot.... kinda. The instructions that came with the manifold gauges are really cruddy. The kit is the brass 2 valve Mastercool set with 72" lines and manual valve quick connects, which is supposed to be a high quality set. I read the instructions and also quite a bit on the internet before hooking anything up. The instructions and everything else I read said to make sure and close the valves before hooking the gauges to the vehicle. Which I did, however I assumed that was to keep the pressure from "shocking" the gauges or something, and after making the connections I opened up the valves, thinking that allowed the refrigerant to the gauges themselves. In reality I didn't understand that the valves on the manifold have no relationship to the gauges, they control flow to and from the yellow service line and also potentially between high and low sides. I figured this out when I decided to hook up to my Dodge (which the AC works great on) and check to see what kind of reading I got on it. The readings from the Dodge were all screwy as well, and thats when I figured something was up. So I read and read and read and found a you tube video finally where someone stated "leave the valves closed when checking pressures".

So now that I've got a real reading from the gauges, I am positive that the system is simply low on refrigerant. My dodges compressor stays on constant for the first 5 or so minutes of operation just like the jeep, but then begins to cycle slowly after pressures and temps are up. Everything on the Jeep is pointing me toward adding some more refrigerant.

[fredjacksonsan]

Sounds like you are right. I would make sure to get the type with stop leak, and perhaps the dye to show where the leak is, in case you need a new hose.

Hopefully the refill with stop leak will take care of the issue.