pTacRP

I've looked far and wide and haven't found the exact answer yet so please don't flame me if this has already been answered a million times. i have a '00 XJ. When I got it the A/C wasn't cold at all. Local shop leak checked it (no leaks) then recharged it. Worked good for about 6 weeks. Now it seems to get cooler when A/C is on but not cold. when A/C is off its just plain warm. Door is switching properly, I checked the motor. When I run the blower full speed (A/C or not) it runs for a few seconds then shut's completely off. After a few seconds it will come back on then after several seconds shut off again, keeps repeating. What is going on???

robertj

Sounds like it's gotten low on Freon again, so I would have to say it does have a leak somewhere. You just haven't managed to find it.

pTacRP

what's causing the blower to go on and off though? I checked the pressure. It was around 55 PSI with the engine off.

toasterknight

Proper procedure for checking pressure is engine running ac on and maxed.

pTacRP

Thanks! Should have checked that before I tested it. Redid it. It's doing repeatedly from ~15 PSI to ~55 PSI back and forth as the clutch (???) kicks on/off. I took a video to show you what was going on:

toasterknight

That means its low on freon again. I would refill with some UV dye and then check to see where the dye is coming out.

Rambler65

An electronic leak detector is nice for finding AC leaks, they've come down in price and are pretty affordable at this point. Definitely helps find leaks in locations where dye would be difficult or impossible to see.

One of the problems with R134a is that it tends to form acids if any moisture is present in the system (difficult to keep it all out) which can lead to tiny leaks in metal parts. Also you might want to invest in a full gauge set for doing AC work, if you can't see pressure on the high side you're only seeing half the story.

It's best NOT to use AC sealers/stop-leak on the system unless it's a last-ditch effort for an old dog that will never be repaired again. The sealers work by hardening on contact with atmospheric moisture. Guess what happens when you open up a system that has sealer in it?

pTacRP

Thanks for the info. When the recharged it and leak tested it they out dye in it. There are no visible leaks making me think that if there is a tiny leak it's in the evaporator core. I'm told that a nightmare to replace 😞

Rambler65

Refrigerant is heavier than air so with an electronic detector you can sniff around the condensation drain to see if the evaporator is leaking. Evaporators are a bear to replace in most cars, which is why sealers are popular. (Typically the entire dash has to come out!) AC sealers can work but as I said can also make a real mess of things if the system is exposed to atmospheric moisture again for any reason. (I have a friend who found this out the hard way.)

If you're lucky it might be the condenser or a hose connection, or maybe compressor shaft seal. There are lots of places in a car AC system where leaks can develop.

This youtube video shows taking out the Cherokee dash "in under 5 minutes" - of course that's with a huge speedup...


If you have to go in there for the evaporator you might as well replace the heater core and blower motor while they're accessible!

madmanmarty

I'm redoing my ac now.
Why is it a ***** to replace the evap if necessary?

pTacRP

you have to pretty much disassemble the entire dash to do it

robertj

He'll get it eventually.

DesertRatCA

I have a 95 jeep Cherokee 4.0 inline 6 cyl. the ac cycles on and off rapidly same with the condenser fan in the engine bay .i hooked a gauge to it and the needle was wrapped all the way around and wasnt blowing cold at idle. then gave it some gas and it started blowing cold and not cycling as much then i hooked up the gauge and it showed it was almost to the red line. so im not sure if its low or over charged. and it does the same all over again. and the gauge i have came from the sub zero r134a can from autozone. any help will be greatly appreciated..

RedRoadRunner

My blower fan was cutting out when the AC was set to max. Every 15 seconds or so, blower would shut down then would restart when i turned ac off and back on. AC system was literally just serviced same day. This continued for a few weeks until the alternator died. I replaced the alternator and i have not had a problem with the blower motor since! If the two were related or not, i'm still not sure, maybe the computer sensed the low output of the alternator and shut down the blower to conserve battery power? I know that is kind of a long shot. Is the computer smart enough to do that?

RedRoadRunner

Blower fan would cycle on/off when AC set to max with fan on high. Did this for weeks until the alternator died. Replaced the alternator and the AC blower now works as it should. If they are related, i dont know. Can the computer shut down the blower fan to save power?