2000 Jeep Wrangler Compressor cycles on and off

  • 6 CYL
  • 4WD
  • 86,000 MILES
The AC in my Jeep stopped working this Spring. When I turn on the AC the compressor cycles off and on every few seconds. I figured it must be low on refrigerant. When I went to add refrigerant I noticed the gauge that comes with the canister goes up and down with the cycling of the compressor, when the compressor turns on the pressure goes to the top of the blue area in the gauge and then it turns off, the pressure drops to the bottom of the blue area and the compressor kicks in again. I did not add any refrigerant since the pressure reading seemed OK. What other problems could cause this?
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Friday, April 25th, 2008 AT 4:45 PM

1 Reply

The a/c compressor will cycle usually because of too little or too much pressure in the system, if ice is present, the thermostat is faulty (or the expansion valve closing). Now at least the operation of the compressor seems to be good other than the fact that it is cycling. The guage should show around 150-180psi (of course this depends on temperature outside) when the compressor is off. This is the absolute pressure of the system +/-20psi between the low and high side. Now when the compressor is on the pressure should fall to around 15-40psi (depends on the temperature outside). Now you may need to get a flow chart for that compressor to find out the specific pressure of the low side given a temperature and volumetric flow set of variables. (I am an engineer so this is important to me but just tell me what pressure you have when the compressor is on and off and record the temperature outside) Check the sight glass on your drier too if you have one. The dryer is located either on the passenger fender right beside the jack or it might be mounted in front of the passenger side firewall. When the compressor is running make sure there are no ice crystals that you can see in there. Note the color of the refrigerant. If it is cloudy or milky then there is probably not enough refrigerant. Ice crystals indicate water inside the system. My guess is that unless you have a hard top the system will never reach ever EVER reach any temperature desireable that a thermostat would cause the compressor to switch off. (I found mine useless so I put an actual switch in and just let it run either on or off at my desire). Lets just start off by a check of pressure and temperature and go from there.
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Tuesday, May 6th, 2008 AT 12:22 AM

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