Ac pressure swing

Hey all, I've got an 03 jeep liberty 3.7. it's an orifice tube system, and I think the orifice tube is stuck open. My low side pressure will be fine while the compressor is on, around 35-40psi, but as soon as the compressor turns off the pressure shoots up to about 65-70 psi , like what would happen when the system is off and the pressures eventually evens out like normal. But this thing is instantly jumping to 65psi the second the compressor turns off, like the pressures are just bouncing back and forth from the low side to high side when the compressor turns off. I'm going to take temperature measurements at all points in the system just to be sure, but am I safe to assume that there's no orifice holding pressure on either side. This system hasn't been running in a year due to some issue, I didn't really get the full history, but I got the compressor running and this is what the pressures are doing. The compressor is cycling too often too so I know it's alittle low on freon, but the unsteady pressures have me concerned. What I do know is some dealership added freon plus oil with dye, because it was out of freon. The tech said on the repair bill he found no leak, which is stupid cause it was out of freon, so I'm worried there's too much oil in it plus these erratic pressures.

I dunno if you can have a stuck open orifice tube? :huh: I've seen plugged orifice tubes due to failed accumulators. Less often, I've seen incorrect orifice tubes installed.

The low side behavior you described doesn't sound terrible to me, but I see new stuff all the time. With the fast cycling and having been topped off once before, I'd suggest verifying refrigerant charge before getting too excited.

What did you do to get the compressor running?

Well this is a friend's vehicle, it had been ripped off a year ago and stopped working 3 days later. He should have brought it right back to the dealership but didn't. I put my gauges on it and the static reading was 65 on both sides, so I figured there should be enough to get the compressor to atleast turn on. But I had no power at the compressor. So I jumped it to get it on for a second just to see where the pressures would go. It worked, compressor came on, low side read about 30, high side about 150. And after that the compressor kept working normally the last few days. so my first thought was that the low side pressure switch is sticking, it's got a pressure transducer on the high side which I checked and it was working fine to begin with. My only real worry was this pressure jumping up and down so fast, usually I always seen a working system jump from about 30 to maybe 40-45. Not 30 to 65 like this. Do you think just low freon would cause these weird pressure reactions on the low side like this? I don't have the means to evacuate the system right now. But something got freed up when I jumped the compressor on. It's cycling now but very quickly. It's been years since I've done ac work since I was living up north, now I'm down in NC and it's all ac work down here. I'm thinking of putting the gauges on it and scoping both pressure switch and transducer all at the same time and see what's going on. Plus taking heat readings at different points. What do you think?

If the orifice tube was missing, or oversize, I doubt the compressor would be able to pull the low side down quickly. I agree with Tyler that low charge is a prime suspect. Personally I'd tell the friend to go grab a couple cans of freon and a case of barley pops

Well now the system is acting crazy, the low side is going to zero when the compressor comes on and the gauge is bouncing all over the place, I think the low side pressure switch is shot or sticking. The compressor shouldn't be coming on with pressure that low. Or possibly a check valve in the compressor isn't working. I'm done with this one. I wasn't even getting paid for this, I'm not wasting any more time on this.