02' Explorer heater/defroster issue

[iamweasel43]

My AC compressor died the other day, fixing that this week, but today I found that when the defroster is turned on there is a slight squeal from around the area of the AC compressor/front of the engine, the engine starts to run rough, but once the switch is moved to the floor vents, the squeal stops and the engine runs fine again. Anyone? Makes no sense to me. Figured out why no air was coming from the defroster but still can't figure out why turning the defroster on makes the AC compressor squeal and almost stall the truck.

Thanks

 

[Number4]

Your AC is used when running the defrost as a means of removing moisture from the air. The noise you hear, is the compressor clutch engaging.

 

[iamweasel43]

Thank you very much, never realized they worked together in that capacity. At least that's one less headache today