Air Conditioning will not turn off

csantur · #1 09-25-2009, 12:53 AM

Hi, I have a 1998 F150 and the A/C allways stays on even in the heat settings. I have changed both switchs the hot-cold and the selector switch for heat, a/c, defrost ....etc. I have checked the blend door and it works fine. Does anyone know what may be causing this?

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cusz28 · #2 10-09-2009, 09:22 PM

unplug your a/c clutch and test for voltage, if it stays constant in different modes that it shouldn't while running, you may have serious electrical problems. if no voltage, and your a/c is still engaged, your compressor is junk. get a new one.

DJ2007 · #3 10-10-2009, 12:08 AM

Quote:

Originally Posted by cusz28

unplug your a/c clutch and test for voltage, if it stays constant in different modes that it shouldn't while running, you may have serious electrical problems. if no voltage, and your a/c is still engaged, your compressor is junk. get a new one.

If the system still cools then the compressor is good. The clutch may be the problem. Couldn't the clutch be replaced without having to replace the whole compressor assembly which would be very expensive?

projectSHO89 · #4 10-10-2009, 09:14 AM

Verify the clutch disengages when it should (ignition OFF). The cluttch plate may be mechanically jammed.

If it's not mechanically jammed in the engaged position, then remove the clutch electrical connector and see if it disengages. If so, there is an electrical fault that is causing a constant supply of power to the circuit.

The clutch may be replaced if needed.

cusz28 · #5 10-11-2009, 04:22 PM

sho, are you just reiterating what i'm saying? sometimes, the clutch cost vs compressor is close enough to warrant a new compressor. personally, I would change the compressor entirely. that way you know that everything is in good working order. you never know if having a jammed clutch messed anything else up. seriously, just ante up and get a whole new compressor.

projectSHO89 · #6 10-11-2009, 08:34 PM

Replacing the compressor requires a hell of a lot more labor and materials than replacing a bad clutch.

I'm suggesting that the fault be diagnosed before making a jump into replacing a part (should one be needed.) Once the nature of the fault is known, an intelligent decision can be made regarding to the cost and scope of the repair.

To replace the whole compressor if only a clutch is required would seem unwise to most people.