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First Start of my A/C is good but when my evaporator is cold, my A/C Goes On and Off Rapidly. On for a second then Off for a Second. Mechanical AC Temperature Slider Does it have to be the Mechanical Temperature causes the problem? Is there a way to repair this thing. If no luck, is it necessary to replace with another Mechanical Temperature Slider Control? By the way, its a Mitsubishi A/C from a Lancer (CB1A).

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Your issue most likely has nothing to do with the control. The reason your system is cycling so rapidly is probably due to being undercharged with refrigerant. There may still be enough left to provide heat transfer (a cold evaporator) but not effectively chill the air. This will cause rapid compressor clutch cycling like you are experiencing. It is due to the system low side pressure dropping below the level required to keep the low drop-out switch closed. This is a safety switch designed to keep you from damaging your compressor running it without sufficient refrigerant to carry the lubricating oil thru the system.

The Fix: Find where your system is losing refrigerant, fix the leak, evacuate the system to remove contaminating moisture, refill with refrigerant and the proper oil if required from repair. If there is no apparent leak and the vehicle has not had the AC serviced in several years, I have seen them slowly lose refrigerant thru the service fittings and system seals. You may be able to get another year out two with just a recharge. ~Jonathan

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