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A.C. stops working after 20 minutes, must turn off+on entire car to get working again

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  • A.C. stops working after 20 minutes, must turn off+on entire car to get working again

    Hello, and thank you for reading.

    I am hoping that some kind person might be able to help me with my problem.

    I have a car that was not released with an O.E.M. A.C., but a previous owner had installed an aftermarket A.C., and I have no idea what brand or make it is.

    When I took ownership, the A.C. did not work at all. I took it to an auto-electrical mechanic, and he managed to get it working, sort-of.


    The A.C. only works for about 20 minutes at a time, before it stops working.

    In order to get the A.C. working again, I need to turn the car off completely (turning just the A.C. off and on again does nothing).

    Once I have turned the car off completely and then turned it on again, the A.C. works fine again, but only for another ±20 minutes.

    The person who fixed the A.C. into its current state has no idea what is causing this. He has re-gassed the A.C. multiple times, as well as fixing all broken components.

    Does someone know what is wrong, so that I can tell the auto-electrical mechanic what to take a look at?

    Thank you for your kind help.

  • #2
    Without knowing the mfg of the system, or electrical diagrams, it will all be a shot in the dark. I have a truck that will lock-off the compressor if a low pressure switch is tripped. Only way to re set is to cut power to the circuit, Turning off the key is one way. I doubt your system uses such a safety circuit.
    It is much more likely that a circuit breaker is tripping. There are several type of circuit breakers used in automotive. One type keeps cycling on and off as it heats and cools. These are often found on critical circuits like headlights. Another type requires mechanical re set (need to push a button to re set). A third type will stay tripped until power is cut and then re sets. My guess is this is what is happening in your case.
    Now the hard part. you need to find which breaker is tripping and then find out why. Hard to do without knowing the wiring. Add to that, you have a modified electrical system and no documentation on the changes.
    Does the fan quit when the A/C quits or does it just get warm? Does it slowly warm or does it all of a sudden stop cooling? When it stops is the compressor still turning?
    My guess is the problem is electrical and not A/C system problem with the gas, but your answer to the above questions will help rule that in or out.


    • achelpneeded
      achelpneeded commented
      Editing a comment
      Thank you for the reply. Apologies for the delayed response. My problem still exists.

      The fan still blows, but it starts blowing warm. It takes a minute or so for all the cool air to get out of the system, but is it relatively sudden.

      I don't know if the compressor is still running. I don't know what a compressor is or what it looks like.

  • #3
    If car is new enough and immediately fitting with A/C yet 1st made without it there are or were certain cars and aftermarket kits in cooperation to install it new with all info known which items + wiring you could tap into along with brackets and all items such that it appeared untouched at a glade other almost universal kits long extinct didn't work for beans right away of the ones I knew.

    Just know how invasive A/C at all is to the entire vehicle is mind bending. Most this IMO shouldn't be done from new (before you) should select a vehicle totally so it can be fixed or service with know designs now seem all missing. It works at all so again IMO job one is find out who made what kit or this could be an endless mess.

    Defaults are going to be reset and shut down many concepts for about anything gets a "grace period" upon starting up till the vehicle is fully at operating temps then switches over to all computer controls that will if it thinks something is out of normal ranges shut it down. A/C does even all OE take time outs for seconds if everything was perfect but knows it's still on and running go back and work again this one isn't getting that message - guesses at best sorry. The best chances is going to be finding the original intentions of the car and this aftermarket kit then go looking for the fault.

    I'll finish to just suggest find out how much this is all going to cost or take as close as can also be guessed decide if you wish to battle on, do without A/C or simply find another vehicle that doesn't have this gremlin and never did. Costs could exceed what this is worth take the hit and bail out seems the prior owner did just that!

    PS: Please state what the vehicle is and what location you are using it in would help a lot......
    MetroWest, Boston


    • achelpneeded
      achelpneeded commented
      Editing a comment
      Car is not new. Please read original posting. What do costs have to do with anything? I want to know what's wrong.

      And what defaults and grace period?

  • #4
    Defaults: It would help a little to know what vintage at least this is but there are mechanical/electrical defaults to "disengage" compressor if way out of pressure ranges. If low is too low just a dumb switch senses that will just cut the flow of power right then and there end it compressing or trying to and should. That is if too low on charge low side also called a suction side may or also may know temperatures but low is either too cold or too low on charge. If too cold you are seriously risking sending along liquid to the compressor which would lock it up.

    Know that refrigerants (condensable gases) have properties to be liquid when compressed and or too cold. Think of a propane bottle for example you never see liquid or shouldn't on those.

    If also a high side installed senses excessive pressure will also cut off power to compressor it's both too much for the system or too hot.

    Defaults: If higher tech and computer controlled if it senses it's empty or way out of range compressors can be shut down till reset gives you a "grace" period suggesting you fixing the problem and it doesn't work properly gives you time to see or charge but only so much.

    Being after market and shutting down after 20 minutes as said top post and subject it's probably just giving you the grace period again without assertively forcing that to work again.

    I/we can't know how it's set up. You could check if power gets to compressor's clutch and it still isn't engaged then there's a problem with clutch's coil (electro-magnet) or gap is larger than it should be with heat can't stay engaged. Tap on it carefully or better yet just check the air gap. Near all are about .020 @ about .030 they can't work well or at all. Can check gap folding a standard paper biz card should be about too tight to squeeze in that air gap if no feeler gauge it can work in a range but not rub.

    Coil could be failing kinda doubt it totally as it resets usually those problems it burned up and stays broken. Check ohms if you wish I think about 4.5 is the aim of most or close.

    Zero or shorted it's messed up for lack of better description.

    May need to watch pressures with system operating gets goofy if you have hoses long enough to watch while driving and can do that without a disaster or just still wait and see what they are hoping it will cut out what the pressures were right away when it did it.

    That's some common reasons on the list. If wires are all screwed up, connections bad or placed near hot things look for evidence of that and move them or replace as needed.

    It's aftermarket makes this back to all basics of how it should work,
    MetroWest, Boston


    • #5
      Without knowing the very basics of the system (what a compressor is and where it is located) I have to say you are way in over your head. I am not saying this to be cruel, but you need to take it to someone who does know the basics of the system. It is not possible to teach A/C work over the internet, nor repair a problem that I can't see or test. Add to that, you have a system that was added and not a factory system.
      We can point you in the right direction if you understand the system and what it is supposed to do, and the basic safeties that can shut a system down.
      I guess I am saying there is a minimum level of system understanding required before you should go anywhere near the system, without that knowledge you run the very real risk of hurting yourself or damaging the system further.
      A/C work can be very unforgiving of mistakes. Ask around in your area for a specialist in A/C work.