Sorry if this post should go somewhere else.

I've been dealing with this issue for a while now and cant figure out the problem. 2000xj 210k miles on it.

During summer months or desert driving in high temps with my AC running & the fan speed on 4, eventually the AC will switch off typically for about 10-30 seconds and then switch back on again. This happens over and over again. It seems to happen when the fan speed is on 4.

A separate issue that may or may not be related is that the air will blast cold for a while and then out of nowhere it will get super warm and I'm better off driving with the windows down and then soon after it will get back to icy cold. It's very odd.

Both of these issues typically occur in higher temperatures, but again I've been having a hard time diagnosing the actual problem.

Thanks in advance for any suggestions.

 

Sounds like a classic case of low refrigerant. Put some gauges on it and report your pressures. Ambient temp and humidity will also help.

 

You're talking about the cans of refrigerant with the gauge on the hose correct? I've used those to charge it and it makes the air temp colder but I still deal with the same issues in high temps. I'll try it again tomorrow though

Another issue I'm having, that may or may not be related is a CEL from a vapor leak that I have yet to find the source of. But I don't think it's related to the AC issues.

 

No, I was referring to a set of manifold gauges.

Here, watch this video:

Get a set of manifold gauges and tell me the pressures on the high and low sides, then we can figure it out. The single low side gauge won't tell you enough. You could also be overcharged.

 

Ok so I hooked up he gauges and here is what I got:




and then when I rev the engine up, the low goes down and the high goes up.

 

You're pics are the same readings. How low does the low side go? How high on the high side? What was the outdoor air temp at the time you did this?

If the low goes down to about 20psi, the cutoff switch will shut it down until the pressure rises back to about where it is right now.

 

It was between 60-65 degrees outside.

I just revved it a bit and the low went down to about 20 & the high went over 300 and then I stopped revving. So I don't think I did enough to get the cutoff switch to shut it down. I can redo it and see what happens.

 

ok I just ran it again and revved the engine and the low went below 20 psi and never went back up until I let go of the accelerator. The high went to about 280 psi

 

You are either really overcharged with a partial refrigerant clog, or your condenser fan isn't coming on (electric fan)

 

what would be the best way to rule one or the other out?

 

Well for one, the electric fan is supposed to come on when the compressor comes on. Does that happen?

 

The fan behind the radiator? that fan is on once the jeep is running. I checked the compressor clutch to see if it engages when the AC is turned on and it does. Is there a different fan you are talking about?

 

Have you serviced the ac recently other than the check pressures?

So when you rev, the pressure drops below 20psi. This would disengage the compressor clutch and shut the fan off, until the pressure rises. No compressor, no cold air. Normally, this would mean an undercharge. However, your high side is high. At 70F (the lowest the chart has) high side should be between 180F to 240F. This is when idling at 1000 rpm.

So a few more things. Is the condenser clean and clear of any mud, leaves or other restrictions? What was the engine temp when you have this happen? When you measured the pressures, were you in direct sun? The reason I ask is that the chart for 90F shows high side at 250-300 psi.

 

No I haven't had the AC serviced at all.

The condensor is clean as I haven't done any off-roading and I keep it pretty clean. The engine temp was a little over 210. The first time I checked, it was at night, then when I re-checked it, it was during the day in direct sunlight, but the results were the same.

 

Well if the fan comes on when the compressor comes on, it's *probably* not air flow. I'm guessing that there's a clog and refrigerant got added until the low side pressure matched the "green zone" on one of those Walmart refrigerant cans with the gauge on the hose type things. In that case, it's overcharged and clogged. You'll need to have the refrigerant evacuated and then you can dig into your system to see if you have "the black death". It's what happens when a compressor dies. It usually gets caught up in the orifice tube and makes a nasty clog.

I'll be honest. I generally flush the lines, evaporator, and condenser with brake cleaner and compressed air. It won't get it all out, but I've never had a problem doing it. Would I risk it on a customer's car? Hell naw. If I open one up and find black death, they get a new condenser, evaporator, compressor, and dryer. The only thing I'll flush is the lines. Is it worth it for you to rip out the dash and replace all the aforementioned stuff? That's your call. I've already said what I'd do. At the very least, you need a new dryer, orifice tube, and probably a compressor. Amazon also sells a really cool AC service kit. It's like $150 and you get manifold gauges, a vacuum pump, and all the stuff you'll need to properly charge the system.