Good day Jeepers
My 2010 JK A/C has a weird problem that my local agent (South Africa) has not been able to fix in 6!!! workshop visits.
When I switch the A/C on it works fine, but after about 10 or so minutes there is less and less air coming through the vents, until there is almost nothing. What air does come out is still cold though. If I switch the A/C off for 5 to 10 minutes it works fine again until the cycle repeats.
I think the evaporator is freezing up, especially since there is a lot of water under the car after the A/C is switched off.
I have found that the compressor clutch never disengages, however if I disconnect either the pressure transducer or the evaporator temperature sensor the clutch disengages. I have replaced the pressure transducer, the evaporator temperature sensor, the fan and fan resistor (all Mopar original parts) and regassed the system.
This is not a climate control system like in newer models, but an old style mechanical system, so no cabin temperature sensor. Oh, and there are no fault codes or warning lamps.
Does anyone have any idea what to look for next?

 

This sounds more like a blower motor issue to me, cuz even if the ac system was failing for any reason, the blower would still be pushing the same amount of air through the vents, it just wouldn't be cold air. That is just my guess with a little logical thinking unless I'm missing something.

 

As resharp001 noted possible blower, if you run the system on med blow in the heat position with temp set for full cold does it still do same. To test if the evap is freezing up when it malfunctions switch temp to full heat which would thaw out the evap and see if the air flow increases back up. Generally when a system freezes up the system is low on refrigerant.. R134a should be in your Jeep.

 

Hi, thank you for replying. The blower and resistor were the first thing I replaced. I forgot to mention that when the problem occurs the blower still runs at full speed. I took it out to check. The thing with the evaporator freezing up, the blower wouldn't be able to push through that. If I put the blower at max speed it works better, but still not quite as it should.

 

Hi, thanks for replying. If I put the system on heat the issue doesn't occur. If I put it on heat or just switch the A/C off for about 5 to 10 minutes it works fine again. Then the cycle repeats. The system was recharged with 134a by my Jeep workshop. And when it does work it is ice cold. One thing I did notice is that the A/C pipes are very hot. I'm not clued up too much on A/C so I don't know if that is normal or not.

 

I’m sorry, I missed seeing you replaced those in your first post. What I don’t get in this scenario is that a shop has not been able to figure it out after 6 visits! Presume when you say you replaced the pressure tranducer and evap temp sensor the shop performed that swap? Only ask to eliminate the idea the system had proper vacuum pulled before refilling. I do see what you’re saying now, and think you’re on the right path of evap freezing, so then the question is why. Can’t rule out that the pressure transducer could have been bad even though new. Possibly really dirty (it is a ’10 model) or faulty evaporator. Do you have an a/c regulator that you can check the pressures yourself to ensure proper refrigerant level?

I am by no means an a/c wizard, but I have pulled a system completely apart to replace on my commuter car. It was a good learning exercise. I just try to think through things logically.

 

The pressure switch snd evap temp sensor were replaced by me, luckily the system does not have to be opened for that. It was evacuated and refilled by the Jeep workshop. I hear you about the old or dirty evaporator, what I don't get is why that compressor doesn't disengage. If the compressor permanently runs there should be too much pressure in the system and the compressor should disengage. If the evaporator freezes up, for whatever reason, the temp sensor should switch the compressor off. None of that happens.