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AC compressor cycle?

Discussion in 'General Chevy & GM Tech Questions' started by Pikey, Mar 25, 2012.

  1. Pikey

    Pikey Moderator Staff Member 3 Years ROTM Winner 1000 Posts

    I posted this in the yukon forum and never found an answer so I thought I could try here. I have noticed that my AC compressor seems to cycle off and on a lot. I understand why it would do it if I had the auto climate control on. Does anyone else notice this with theirs? Any ideas why this does it? How to fix it? Seems like I could be losing MPG and wearing the compressor. The compressor clutch turns on as soon as I turn on the climate control switch and it stays on. Whether it be on full heat or not. When the ac is on it is cold. I switched the relay out with a know good one and still have the same issue. I have been driving with the windows down and the climate control off and my MPG has increased. Any thoughts would be really appreciated! Thanks
  2. dedmon27

    dedmon27 Rockstar 100 Posts

    Don't know a whole lot about a/c but I do know that when the defrost is on the pump will kick on. The manufacturers did this to keep the system cycling during the winter to keep all the o-rings and other compnents lubricated. Thats why the majority of the systems lasted longer (no leaks) now than when the a/c systems first came out.
  3. Pikey

    Pikey Moderator Staff Member 3 Years ROTM Winner 1000 Posts

    I understand a little about a/c. I get that it runs during defrost to remove moisture from the air. But, that is the extent of my knowledge of it. I know there is a high and low side, a compressor, a condenser, a relay, 134a. and a control panel. That is it
  4. Pikey

    Pikey Moderator Staff Member 3 Years ROTM Winner 1000 Posts

    I spoke with a mechanic I know. He said that it could be the control unit or a module that controls the system. I have a friend trying to locate a good control unit, I will swap them out and try it. If it is not that I may actually have to pay the dealership to look at it!! That will not be cheap.
  5. Pikey

    Pikey Moderator Staff Member 3 Years ROTM Winner 1000 Posts

    I noticed a while back that when I turn the AC on the snow flake on the screen has a line thru it. Is that normal? It has the auto climate control system.
  6. 08_rado_rocker

    08_rado_rocker Member 2 Years 500 Posts

    Hey bud.. there's a sensor on your compressor that kicks your compressor on/off based on pressure. This switch could have gone haywire, or your system could be low on 134. Just a possibility I'm throwing out there to keep from replacing any unnecessary/expensive control units. I hope this helps. Keep us updated! :)
  7. csltrains96

    csltrains96 Rockstar 100 Posts

    I agree with 08_rado_rocker. When the compressor gets low on refrigerant, it will cycle more often to maintain the high and low pressure differential. Your AC can still be cold, but needing more refrigerant. Also, your refrigerant contains the lubrication for the AC compressor, so having it cycle more frequently also means it is probably in need of more lubricant.
  8. Pikey

    Pikey Moderator Staff Member 3 Years ROTM Winner 1000 Posts

    Ok, Thanks guys! I will borrow a gauge from my neighbor and see how much is in there.
  9. 08_rado_rocker

    08_rado_rocker Member 2 Years 500 Posts

    Good idea, If there is plenty of 134 in the lines, then my first thought would be that the sensor has taken a crap and causing the cycling. It would be cheaper and easier to replace than the likes of a control unit. I think the last one I bought was like 20$ at vatozone
  10. Pikey

    Pikey Moderator Staff Member 3 Years ROTM Winner 1000 Posts

    When you replace it do you have to empty the system? I would be getting the control unit for free (if one can be found) I know someone that works at a place that brings in new cars and trucks then rips the interior out and throws all the parts in a dumpster, of course they cut all the leather seats with a knife first. They do this so they can test fit new dashboards and seats.

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