Anonymous asked in Cars & TransportationMaintenance & Repairs · 2 months ago

Does a car AC compressor runs all the time?

My Ford Crown Vic 2005 had low refrigerant and compressor would cut off even on normal acceleration (not wot). Low side pipe that should be icy cold would always stay very very slightly cold. Today after fixing a leaking hose and recharging  the system, AC is blowing icy cold air and low side pipe is freezing cold but now compressor is not running constantly like it runs for 30 seconds and then disengages for few seconds and then again comes back on. I can hear compressor engaging and disengaging but cabin temperature stays cold. Is it normal now or was it normal before ? Low side is around 35psi but I don't exactly remember the high side.

9 Answers

  • Anonymous
    2 months ago

    No, it has a clutch that slips when it does not need to get colder inside the car.  You temp control in the car said cool (it did not say make ice) so the AC senses it is close to the right temperature in the car.  It works like the thermostat for the furnace in the house in the winter.  It runs and shuts off occasionally once room temperature has been reached.

  • fuzzy
    Lv 6
    2 months ago

    There is a thermostat at the oulet of the cooling coil. When the coil approaches freezing point it stops the compressor, otherwise the coil would freeze up & no air air could get thpough it.

  • M.
    Lv 7
    2 months ago

    Did you evacuate the system before you charged it? 

    Did you charge the recommended amount of refrigerant?  It's generally posted on a sticker under the hood somewhere. 

    What is the outside temperature? 

    What is the duct temperature? 

    What is the high side pressure? 

    35 psi low side pressure means an evaporator temperature of 40° F.  That means your duct temperature is probably around 45° F. 

    It's not bad. 

    It might be a little lower if your method was more precise. 

    Most CCOT systems don't run continuously.  They cycle. 

    Cycling Clutch Orifice Tube. 

    The systems with a TXV generally run continuously and the TXV modulates. 

    Thermostatic eXpansion Valve. 

    -General automotive mechanic since 1972 

    -AC repair since 1980

  • 2 months ago

    I don't know about your car but I had a Pontiac G8 and that thing ran constantly. My AC belt flew off a few times because of the faulty design.

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  • 2 months ago

    It turns on and off as needed, not constantly. Enjoy your AC.

  • Anonymous
    2 months ago

    The AC is working fine.  It is cycling as advertised.

  • 2 months ago

    Its normal for it to kick on and off - that's why there's a clutch between the pulley and the compressor.

    The other accessories that are driven by the accessory belt don't have clutches because they never shut off when the engine is running. But the AC compressor doesn't need to run continuously so its designed to engage & disengage with the clutch.

    Sounds like you found and fixed the leak, refilled the R134a, and now your system is working properly - congrats on a successful DIY repair.

  • 2 months ago

    You're low on 134a yet. Add more 134a and the compressor will quit cycling on and off.

  • Rick
    Lv 7
    2 months ago

    nope, it shouldn't, it's an electric clutch, so electricity can turn the A/C on and off ......

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