1998 Explorer Sport, V6 OHC

Replaced orifice tube, leak checked, evacuated and refilled. Good pressures. Replaced a/c cycling switch on accumulator.

Evaporator freezing on MAX cool, i.e. compressor stops. This happens regardless of position of cabin thermostat on MAX cool. If I go to fan only and wait a few minutes and return to MAX cool, compressor will engage again. Then repeat above.

Does not freeze up on just a/c. Using outside air, compressor cycles normally, no freeze up.

My wife has allergies and MAX air helps a great deal.

Thanks so much.

 

Are you sure the evaporator is actually freezing? If it is, just about the only thing that will cause it is a flaky cycling switch or slightly low system charge. Normally the compressor doesn't stop running altogether.

If the switch doesn't turn the compressor off at the right Low Side pressure (too low), the moisture on the evaporator will freeze.
I don't know the physics behind the low charge causing evap icing, but I've always been told it can. I can't say I've ever seen it actually happen.

Look down inside- the electrical connector on the switch between the pins. There "may" be an adjusting screw. If so, turn it clockwise about 1/8 turn. This will raise the cutout pressure 1-2psi and should solve the problem.
If there is no screw, try a new OEM switch.

 

The AC unit can freeze up in strange places with too low of a charge....due to ideal gas law Pv=nrT....v, n, and r are constants...so if pressure drops, so does temp....and if there isn't enough freon/charge...this can happen in places that it is not supposed to happen in.

Good luck!

Milkman