Compressor cycles a few times then...nada

Did the usual add 134 and it was low, got up to ~40psi and the clutch started to engage and disengage 1-2 seconds at a time for 4 rotations then would never cycle on again. Figured it was the pressure switch, so few days later installed the new pressure switch, checked low side pressure again and same thing clutch would cycle on and off 3-4 times then nothings.

If I let it set for an entire day and then fire it up it goes through the same clutch cycle pattern then nothing. Only way I can get it to go through the cycle pattern again is if I let it sit for at least a few hours.

Anyone got any ideas? It was originally only a little low and since I charged it its held pressure fine. I did jumper the pressure switch thinking maybe the new one was bad and no change. It isn't stuttering/jerking and when it does energize it goes instantly to full rpm so I know its not the clutch itself. I did a ton of searching and only solid lead I could find was maybe the orfice tube?

I don't know a ton about refrigerant stuff, but your orifice tube theory sounds completely plausible.

Your symptoms remind me of a plugged vent on a motorcycle gas tank. Runs great for a little bit then starts sputtering because a vacuum has formed not allowing more fuel to leave the tank and the carb bowls begin to run dry.

what year is it? does the electronic fan kick on if you jump the low pressure switch? also check the a/c compressor clutch relay.

the only other thing i can think of is the fin sensing switch.

also the xj's do not have an orifice tube. they have an expansion valve.

whats the static pressure after it has been siting for a while. if its at 40 sitting its too low. should be ~100 depending on the ambient temperature.



FIN SENSING CYCLING CLUTCH SWITCH:
The switch is attached to the evaporator coil with the
temperature sensing probe inserted into the coil fins.
This switch controls evaporator temperature and prevents
condensate water on the evaporator coil from
freezing. It does this by sending signals to the Powertrain
Control Module (PCM) to cycling the compressor
clutch on and off. This switch is used on XJ
only

Its a 99. I'll check the fan when I get back intown Sunday. So when I jumper the LP switch it should turn on immediately? Didn't think to check the relay since it does kick on and off, you thinking the relay is 'popping'?

Is there an easy way to get to the fin sensor or do I have to do the usual dash teardown to get to? I know in my grand I could barely get a hand through the blower housing.

The later XJ's used an orifice tube in the liquid line. The orifice tube is embedded in the line so to replace it you have to change the entire liquid line but they are not that expensive.

The A/C requires both the LP and HP switches to be closed.

It would be interesting to see what the HP side reads.

A/C compressors get hot quickly, and thats ok. But they have a built in thermal fuse. If it gets too hot internally for whatever reason, the thermal fuse opens and it stops working until it cools down. Then it works again. Have the compressor thermally tested. If it is the fuse, replace the compressor, there is no way to change out the fuse.
Just another idea for you.

Ok I had a similar issue on my 01 . What mine ended up being was the clutch was worn out of spec. there is a shim between the armature and clutch plate. If the plates wear too much that gap is out of spec for the clutch to pick up and hold in. You can check this gap and add or remove the shims as needed as described in the manual.

http://http://www.sanden.com/servicemanual.htmlwww.sanden.com/objects/TR Service Manual.pdf
This may not be the exact model but the inspection and adjustment is similar

http://www.sanden.com/servicemanual.html

Hope this helps it fixed mine for the time being.


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clutch works fine if I jump it straight to the connector, so something is telling it not to turn on... so the fun begins figuring out what that is.

Yea check your hp switch it should be a double pole one for the fan relay and one for the clutch so make sure it is operating properly on both poles


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whats your static pressure when the system is not running? it should be about ambient temperature. you may have an undercharged or overcharged system.

My 99' has similar issues not quite as bad. In mine the compressor will just stop running for a few minutes on the drive home and then sporadically kick back in. It is temperature related in my case, as this is not an issue if temps are below ~85* or so.

Last night I was able to make it home with the compressor not running. The electric fan was running, un-plugging the low pressure switch did turn off the fan, telling me the switch was in the proper position. Removing the ac clutch relay had no effect on the fan and could be felt clicking when reinstalled.

I think the issue is with the relay and I intend to replace my relay and see if the issue persists.

Based on reply from the others, jumping the high pressure switch connector could be an interesting test. Perhaps the computer sense the a "over pressure" situation, and continues to run the fan, but does not engage the compressor. However the relay is clicking when inserted, so I still think my first test will be replacement of the relay.

Does anybody know where to find an electrical diagram of the AC Clutch control system for the 97-99 era?

Jeremy,

99' 4.0 AW4 NP231.

Whats your high AND low side pressure readings? Cant diagnose it unless we have these readings as a base. Also, you said you 'charged' it, what machine did you use, that would def help in determining your issue.

ok problem solved. Looks like both my switches were bad. After replacing the HP switch and then jumpering the LP switch it now comes on and blows cold. Who would have figured both were bad!

Next question is does our system have a Schrader valve on the LP switch(like the HP) or will it open up the system forcing me to do a vac and fill at a shop? I see a lot of guys on here just jumper the connector so I'm guessing that's why....

yes you can swap the switch with out purging the system.

Low psi Control opens < 25 psi - resets > 43 psi
High psi Control switch - opens > 450-490 psi - resets < 270-330 psi

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.

Tampa_XJ, when your compressor cut out, did the fan also stop running?

yes, however if I pulled the a/c comp relay the fan would then turn back on. When I plugged the relay back in the fan would cut back off.

So with hvac set to max a/c and the broken lp switch the electric fan would cycle on and off with the compressor. if I unplugged the comp relay the elec fan would instantly start up and stay on. If I plugged the relay back in the fan would stop. Again this was with the broken lp switch.