I have a ford fusion 2012, with mileage around: 140,000 km. Since last week, it happened 3 times that AC stopped cooling while driving. I had to turn it off/on for 2 or 3 times to turn it back to cool. Degrees nowadays here is around 110f which is not possible to survive without AC.

I asked a mechanic and he directly said that it is an issue with AC compressor and would cost around $9k to replace. I tried to google this issue and some suggests to just replace the AC sensor which would cost not more that $100.

How can I know the exact cause of this issue?


  • put it on a test rig and check charge level, pressures, flow rate etc
    – Solar Mike
    Commented Jul 9, 2018 at 6:31
  • Sorry, but how can i do that?
    – AlBaraa Sh
    Commented Jul 9, 2018 at 6:54
  • go to a garage that has an a/c test system and get them to run a full diagnosis... Unless you plan on buying one yourself...
    – Solar Mike
    Commented Jul 9, 2018 at 7:02
  • When the AC stops cooling, does the clutch hub on the compressor's pulley stop rotating?
    – Al_
    Commented Jul 9, 2018 at 9:33
  • I didn't check that. I'll check it as it happens again. Thanks for your question :)
    – AlBaraa Sh
    Commented Jul 9, 2018 at 9:36

1 Answer 1


What engine have you got? Even better, what compressor have you got? (drop down in the engine bay and check the label on the compressor).

Your issue may simply be a faulty AC clutch coil relay. Find it, identify the relay and then replace it. Begin with the simplest thing, the relay. It's the cheapest fix. You'll have to look on the net pretty hard to know where this relay is located (like i had to do), unless Ford was kind enough to provide a relay scheme in your car's manual.

Just don't understand why mechanics want to change the whole compressor as soon as the AC starts acting up. A new compressor is needed only when the old one seizes or is about to seize. Drop down in the engine bay with engine off and keys in pocket and turn the clutch hub in front of the compressor's pulley with your bare hands, and feel for an uniform and smooth resistance for one hub turn. If you get this uniform and smooth resistance the compressor's good and even if the fault is in the compressor the fault may simply lie in one of its control systems (clutch coil, clutch assembly, control valve, thermal switch for example). Even if the compressor is seized, go to the scrapyard, fetch an old one, check if it's still good (look for any oil leaks, rotate the clutch hub and pulley with your hands, check for coil continuity) and then fit it on your car on a flushed AC system (with a new condenser and a new receiver dryer) after loading the compressor with the proper amount of oil and "priming" it, no need for a new one. You can source a clutch coil or clutch assembly from an old compressor too, and in the meanwhile you can keep the old but still good compressor until you need it, or even sell it back as a core if you may like. Learn how to be your car's tech, and nobody will try tricks on you.

However please tell me your engine model or, even better, compressor model. It's important info because every compressor has different control systems. The scroll one for example has a thermal switch which may trip early if faulty or on time if the compressor is getting too hot. The Sanden one has a control valve which may be faulty (and, to replace it, the compressor has to be opened).

Another thing: the AC sensor you're referring to might be an evaporator temperature sensor. In that case, the Sandens don't need it because the control valve inside them regulates refrigerant flow avoiding evaporator's frost. The Visteon scrolls, instead, need it.

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