AC Not Working at Idle

Discussion in 'Ask An Owner Operator' started by gregbo, May 24, 2019.

  1. gregbo

    gregbo Light Load Member

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    Have an '02 Century with Detroit 60. AC works while rolling but not at idle. Compressor runs for a minute, shuts down, starts again, shuts down etc. Looks like it's not turning on the engine fan. Which switch, relay or circuit should I be looking at? I know very little about AC so please make it as simple as possible. Thanks.
     
  2. Cam Roberts

    Cam Roberts Road Train Member

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    first thing i was gonna say is pull out your gauges and check your pressures but that shouldnt matter if the truck is idling or full bore. Never had that issue before so im subscibing to see what others say would cause that situation
     
  3. gregbo

    gregbo Light Load Member

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    Yeah runs as long as air is cooling the condenser while driving but not turning on the fan at idle. Starting to get hot out there and I'm gonna need it.
     
  4. razor1983

    razor1983 Medium Load Member

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    High preassure switch, it’s on the ac dryer
     
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  5. Antinomian

    Antinomian Road Train Member

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    Does your fan come on when the compressor stops? The reason it doesn't cool when idling is because the fan is supposed to come on and the compressor is supposed to stop when the freon pressure is high.

    Does the fan come on at all? This could either be an AC problem or an engine fan problem.
     
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  6. Ridgeline

    Ridgeline Road Train Member

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    Omg ... people ....

    Op clean the condenser.

    Loosen it all up so you can get some medium pressure air and blow it out from the back to the front. Then do the same thing with the radiator and ACA to clean all the crap that has accumulated.

    Pretty sure this will fix your problem, it should be done ever couple years anyways.
     
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  7. Antinomian

    Antinomian Road Train Member

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    He said it isn't turning on the engine fan.
     
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  8. Rideandrepair

    Rideandrepair Road Train Member

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    It’s probably the high pressure/ fan switch on the air drier, as others have mentioned, If I’m not mistaken, it’s a bianary ( Double) switch. Sounds like the fan half of the switch isn’t working. It’s the one on top of air drier with a short harness/ pigtail on it. The other switch is low pressure switch.Its good, otherwise compressor wouldn’t come on at all. If Replacing the bianary switch doesn’t get the fan working. You have another problem somewhere else. Fan selinoid maybe? Either way fan should come on when idling and compressor should also cycle off. Till pressure drops. Staying on longer than off , even on the hottest days. Hotter temps and higher humidity causes higher pressures, causes more cycling.Overfilling system will also cause it to cycle off for too long. Sounds like you have a fan problem. Make sure condensor and radiator fins are all clean for good air flow. So the fan can do it’s job, pulling air through fins, once it’s fixed.Simple answer change bianary switch, simple 7/16 wrench and a plug. You won’t lose any Freon in the process.Unscrew old switch slowly.
     
  9. truckdriver31

    truckdriver31 Road Train Member

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    7F82BAE6-3D96-4514-A2C1-E590CAFC33C7.png 17FD13B9-8531-4F7C-8FC7-A9440535EECF.png
    gauge it
     
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  10. truckdriver31

    truckdriver31 Road Train Member

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    put paper clip in the plug. see if it comes on. but truly need to gauge it
     
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