[NCWRANGLER]

New to the forum. I have a 2006 Wrangler X that will not cool well on hot days. AC works great in the morning (around 70 degrees) on the 20 minute drive to work. Vent temp stays about 45 degrees and the compressor seems to stay on continous. In the afternoon when driving home from work with outside temps around 85-90 degrees, the AC will work fine for about 5-10 minutes then the compressor will start to cycle on and off every 6 seconds while driving and the inside vent temprature will rise to 52-58 degrees. If I happen to stop on the way home and then restart the engine, sometimes the compressor will not click on for several minutes and when it finally does it will still cycle rapidly and not cool very well.

I have had it at an AC shop and they said it was low on freon and they evacuated and recharged with no improvement. They said it might not be freon related. Then I took it to the Jeep dealership and they evacuated and recharged and said it had too much freon. That did not help either. It is now at the dealership again and the technician is driving home at night but has not found a cause yet. Im not sure he is an expert on AC but he thinks that high pressure is causing the compressor to cut out rapidly. I really would like to have my jeep back and fixed. I did not see anything on a search that showed a similar situation. Can anyone help with other items to check. Thanks

[Malebolgia]

Best thing to do is remove the A/C system and drive around with no top.

[Dogman]

Mine cycles on and off a lot as well. Except my AC is super cold. It drives me nuts. Pressure is within the normal range and the whole system is only 1 year old. Had the initial evacuation and leak test done by professionals. Charged it myself.

I'm wondering if your low pressure switch is bad?

[TheBoogieman]

NEVER take your Jeep to the stealership for work,especially A/C work.There's no need to evacuate the system to add R134a(not freon).I bought a gauge and refill kit for $25-30.If it's really hot outside,it will cycle on and off more.If it's overfilled,it will cycle very little.You can check it yourself with the gauge and add or remove the R134a as needed.I even had a leak that was fixed using the ID brand super leak stop.
IDQ - Auto A/C Products & Sealing Solutions

[masol]

The AC system has high pressure protection, a switch installed normally near the condenser, some systems also has a low pressure protection, you can check if it is doing the on/off cycle, the contacts are normally closed, meaning that you can disconnect the cables from the switch and using another piece of cable connect both terminals, the AC compressor should remain on, if your AC system has also a low pressure switch do the same test.

If the high pressure switch is the one that is doing the on/off operation you need to verify if the condenser fan is working, when you turn on your AC, the condenser fan must be on always, some cars has only one fan for radiator and condenser, must be on when AC is on. Take a look of the fan, because I had one car with the same symtoms and the problem was the fan bearing got stock with mud and the normal speed was not reached, just added some cleaning, oil and problem solved.

If the problem is not the fan, and high pressure is the switch doing the on/off operation could be excess of refrigerant, you need a gauge and see if it is in the red zone, need to extract some.

If the problem is low pressure, and high mesaurement is in green or lower you need to add refrigerant.

Hope this helps, if the problem persist, add more info the post and let see if we can help.

[Dogman]

From the FSM:

LOW PRESSURE CYCLING CLUTCH SWITCH
The low pressure cycling clutch switch is located
on the top of the accumulator. The switch is screwed
onto an accumulator fitting that contains a Schrader type
valve, which allows the switch to be serviced
without discharging the refrigerant system. The
accumulator fitting is equipped with an O-ring to
seal the switch connection.
The low pressure cycling clutch switch is connected
in series electrically with the high pressure cut-off
switch, between ground and the Powertrain Control
Module (PCM). The switch contacts open and close
causing the PCM to turn the compressor clutch on
and off. This regulates the refrigerant system pressure
and controls evaporator temperature. Controlling
the evaporator temperature prevents condensate
water on the evaporator fins from freezing and
obstructing air conditioning system air flow.
The low pressure cycling clutch switch contacts are
open when the suction pressure is approximately 141
kPa (20.5 psi) or lower. The switch contacts will close
when the suction pressure rises to approximately 234
to 262 kPa (34 to 38 psi) or above. Lower ambient
temperatures, below approximately -1° C (30° F), will
also cause the switch contacts to open. This is due to
the pressure/temperature relationship of the refrigerant
in the system.
The low pressure cycling clutch switch is a factory calibrated
unit. It cannot be adjusted or repaired
and, if faulty or damaged, it must be replaced.

HIGH PRESSURE CUT-OFF SWITCH
The high pressure cut-off switch is located on the
discharge line near the compressor. The switch is
screwed onto a discharge line fitting that contains a
Schrader-type valve, which allows the switch to be
serviced without discharging the refrigerant system.
The discharge line fitting is equipped with an O-ring
to seal the switch connection.
The high pressure cut-off switch is connected in
series electrically with the low pressure cycling
clutch switch between ground and the Powertrain
Control Module (PCM). The switch contacts open and
close causing the PCM to turn the compressor clutch
on and off. This prevents compressor operation when
the discharge line pressure approaches high levels.
The high pressure cut-off switch contacts are open
when the discharge line pressure rises above 3100 to
3375 kPa (450 to 490 psi). The switch contacts will
close when the discharge line pressure drops to 1860
to 2275 kPa (270 to 330 psi).
The high pressure cut-off switch is a factory-calibrated
unit. The switch cannot be adjusted or
repaired and, if faulty or damaged, it must be
replaced.

[MattJeep]

Your low on Freon. Its probably just leaking out somewhere. Does the cycling stop after you have the system recharged then just come back after awhile?

[NCWRANGLER]

Thanks for the replys. Masol- this Jeep only has has the one radiator clutch fan that is belt operated from the engine. No electric fan. When the engine is hot I can still turn the clutch fan by hand. You cant spin it but you can turn it with moderate pressure. I was hoping this might be the problem but I checked another jeep like mine and the clutch can be moved fairly easily on it as well.

Mattjeep-The adding of freon did not change the problem. The dealer actually removed a little bit of freon and that did not help either. I think it call for 1.25 lbs.

Dogman, I do have 2 pressure switches. Could either switch cause this type problem. Also everything works normal in the mornings when the temp is around 70 degrees but if the temp is 80-90 degrees, the compressor starts cutting out.

[wushaw]

[QUOTE]Dogman, I do have 2 pressure switches. Could either switch cause this type problem. Also everything works normal in the mornings when the temp is around 70 degrees but if the temp is 80-90 degrees, the compressor starts cutting out.[Quote]

The low press switch is the most likely culprit but then again it could be working correctly and something in the system is like the expansion tube may not be working correctly.

[DstroyrOfWrldz]

Originally Posted by Dogman

From the FSM:
...

The low pressure cycling clutch switch contacts are
open when the suction pressure is approximately 141
kPa (20.5 psi) or lower. The switch contacts will close
when the suction pressure rises to approximately 234
to 262 kPa (34 to 38 psi) or above.

for reference, that's a cut out of about 22°F saturated suction temperature, and a cut in of about 41°F.

The high pressure cut-off switch contacts are open
when the discharge line pressure rises above 3100 to
3375 kPa (450 to 490 psi). The switch contacts will
close when the discharge line pressure drops to 1860
to 2275 kPa (270 to 330 psi).

HOLY **** that is high for an R-134a system. I'm fairly sure 450psi is above the critical pressure for R-134a, it's not even on my PT chart. I engineer commercial and industrial air con and refrigeration systems and we normally have a 350lb pressure relief valve on 134a systems, and the high pressure safety (which is manual reset, not automatic) can be no higher than 90% of the PRV rating - so ti's 315psig.

You would have to be RIDICULOUSLY overcharged for the high to be playing a role. The condenser would be around 200° or more.




Here's the thing about charging an automotive system. It's not an exact science. True, the only way to get it right on the dot is to evacuate it and weigh it in, but you can get it working just fine by charging it until the suction line is "beer can cold". I'm serious.

[b912]

You've been given some really thorough advise in the past few responses so this is pretty lame but....it's a jeep thing. I haven't seen a TJ with AC that didn't cycle what seemed to be accessively. I have an absolutely brand new AC system top to bottom and it's ice cold in 80 degrees and much much worse above 90 degrees. I've read that they just don't blow that cold in dreadfully hot/humid conditions.

[TheFog]

Originally Posted by DstroyrOfWrldz

HOLY **** that is high for an R-134a system.

You design any R-410 systems, now those are some pressures !!!. I know a couple manufactures were having problems with their high pressure cutoffs with units operated in high ambient temps like Arizona.

I sure am going to miss R-22

FOG

[alexfiggy]

i live in miami its ****ing hot!!!!my a/c cycles like a machine gun since i got her in 04.as long as it blows cold your good to go.

[DstroyrOfWrldz]

Originally Posted by TheFog

You design any R-410 systems, now those are some pressures !!!. I know a couple manufactures were having problems with their high pressure cutoffs with units operated in high ambient temps like Arizona.

I sure am going to miss R-22

FOG

Much more often than 134a, actually. We use a 650psig PRV and a 585psig high pressure safety for 410a.

Fortunately the industry finally seems like it's catching up - there for awhile it was hard to get components rated for the pressures. Even still it's difficult for us because most of the 410a development has been for residential and other small stuff. It's still no fun sourcing components for a 50 ton per circuit 410a system when everybody but the compressor manufacturers seem to stop around 15 tons.

[NCWRANGLER]

Heard back from the jeep dealer today. He hooked up gauges, voltmeters etc and was able to watch it act up while driving it. He is convinced it is the low pressure switch and that it is somehow losing ground or malfunctioning when it gets hot. Not a single one to be found in the US--96 are on backorder already. Some others must be having problems with the switch as well. Thanks for the input guys. Any ideas on getting a switch.