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A/C compressor stays on constantly

Ford Taurus 2000. Story, I could not find a coolant leak so ended up taking it in. Was the resevour, fixed, alls good. Just before I drove off I asked the guy if anything else needed attention, he said “nope, wait, your air compressor stays on for all control settings except off”. “Is that a problem?” “Not really, little less MPG, and when it gets really cold out it may not heat properly” Well, MN winter here, and yes it does! When it gets to about +10 degrees or colder the heat turns to warm. Colder outside and the heat turns to cold! He thought maybe the control needs replacing. Anyone know the answer?

If you have auto-climate control, this is exactly how it is supposed to work. On both of my Lincolns, the AC compressor runs all the time, summer and winter, if the control is on any setting other than off. (I just leave it on full auto all the time anyway.)

During the winter months, you COULD simply remove the wiring connector from the compressor…This might reduce defroster efficiency somewhat…Or you could install a dashboard mounted switch in the compressor wire so YOU could control its operation as desired…

As tardis stated. Your climate control system is working as Ford intended. If your car is not putting out enough heat it could be the heater core is partially clogged, and needs flushed. Or perhaps the water pump may not be flowing enough coolant because off impeller fins rusted away.

As for the A/C running at +10F outside temperature. This is unlikely because the refrigerant pressure is relevant to temperature. So at 10 degrees outside temperature the pressure of the refrigerant is lower then the pressure needed to engage the pressure switch that allows the compressor to run.

Thought about doing that…but decided I would probably mess something up. Plus I blow a lot of hot air, and I can’t stand foggy windows in the winter!

Thanks for the good info and tips! How would I tell if the fins on the water pump are shot. Is flushing the core something a handy novice can do or is it best left to the shop?

I recall my 97 Taurus A/C ran in all modes except off, and vent mode. If your car has a vent mode see if the compressor runs in vent mode, if not you can run the heat in vent mode without the A/C ever running.

Which engine is in your car a Vulcan or Duratec? Assuming its a Vulcan flushing the heater core is a simple matter of.

  1. Properly draining the coolant into a container.

  2. Remove one heater hose at the coolant thermostat/sensor housing.

  3. Remove second heater hose at water pump and direct it into a catch container under the car.

  4. with a garden hose, flush water through the top hose catching the water in a catch container below the car. Note there may be a rubber bypass hose between the two lines that needs temporarily flatten with pliers to get the full force of water through the heater core.

    “How would I tell if the fins on the water pump are shot” This would require removal and inspection. If the coolant is brown, and rusty with a lot of sediment then the chance are good.

Sounds good, thanks. The a/c compressor even runs in vent mode. The only way to shut it down is to turn the whole system off. Still seems wierd why Ford would keep it on for all modes. What is the point of the AC and AC Max settings then? I can get the same result from vent!
Thanks for all the help