Question about 1999 Ford Crown Victoria

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Trying to figure out what controls the power to a/c compressor

Trying to figure out what controls the power source that sends power to the a/c compressor. My compressors has no power to it

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  • mikef257 Jun 25, 2009

    Thank you Molson02536. I was able to get power to the compressor. A new problem has arrised though. The compressor kicks on for 8 seconds then off for 10 sec. It continues to do this. The a/c system does not get cold. My a/c gauge says there is the right about of freon in the system. Also when trying to add more freon to the system it wont take any more. Any ideas?????



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The A/C pressure switch along the low pressure side if the right amount of pressure in the system will be at a close circuit sending signal to the A/C clutch realy's which sends power to the A/C clutch to engage when prompted by the heating and cooling system in the dash. If the A/C system is low on R134a, the system will not work since there is not enough pressure for the pressure switch to have a close circuit. The pressure switch should be along the low pressure side on the line of on the Air Dryer, ( Looks like a silver cylinder ) Check the fuse box under the hood close to the battery, there should ne a high amp fuse for the A/C and the relay's may be in there too. Good luck and hope this helps. Keep me posted , be glad to help. 

Posted on Jun 23, 2009

  • Harvey N Tawatao
    Harvey N Tawatao Jun 25, 2009

    Moisture causes internal icing that obstructs the orifice tube or expansion valve. This can create excessive high pressures and low cooling. The A/C system is a closed loop system so why does it need a Drier to remove moisture? Here's how moisture gets into the system. Refrigerant charged through service hoses not evacuated after being connected to the system will have air and moisture in them. Hoses left uncapped while replacing components allows moisture to enter. Refrigerant oil is hydroscopic (water absorbing like a sponge) and left uncapped will have moisture in it. Recycling machines with old filters will not remove moisture from incoming refrigerant. Condensation created when the Low side of the system gets cold and then warms up when the system is turned off is absorbed into the system through the hoses. Systems low on freon will pull moisture into the system when they go into a partial vacuum.  The Low side should have 30psi to 50psi, the high side should have 150psi to 200psi any other readings will have poor performance and high readings will cause system damage. Keep me posted, be glad to help you keep cool. Let me know what your low side is with the a/c running on max. 


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First check the fuses, then check if you have enough freon in system. If there isn't enough, the "LP Switch" - a switch on the suction side (thick pipe on compressor) will not switch the system on, it is there to protect the compressor. Have some freon put in, if it works and a few days / hours later it doesn't work, then you have a leak on the system.

Posted on Jun 23, 2009


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