2004 1.8 Sentra A/C Compressor issue

My friend is having a strange issue - regardless of whether the A/C button is pressed in the dash, the compressor is turning on whenever you kick the fan control past 0. I've let the car sit in the sun all day on a hot day, cranked on the heater on recircluate for a few mins, then turned the temperature knob back to cold and it blew cold in a few seconds. When you just nudge the fan speed from 0 to 1 you can hear the compressor sound like it's kicking on..

It's blowing cold like it should be, but we can't figure out how to make it stop. Any ideas?

Sounds like the A/C button has internally shorted and is now always on, or somewhere in the wiring harness it has shorted, I would start with testing the button.

when you defrost your car, the ac compressor comes on, any time after that the compressor stays on unless you run it to wide open throttle or turn off the car, it is built into your ecu, its purpose is to remove humidity from the air when defrosting the windshield, dont know why it stays on permanently but its built in there for a reason i guess

That makes sense, I have a '99 Suzuki Esteem that is so sealed up that if more than one person is breathing in the car the windows fog up so badly that the car is not drivable unless you turn the A/C on and have it blow all the air up on the windshield, then it clears up in less than a minute.

it sucks when its cold and you defrost the air and then it gets too hot so you turn it to cold and it frosts your windows back up because the compressor doesnt turn off though.....

My Suzuki will run the heat with the A/C on, just the adjust the heat where you want it, the A/C acts just like a dehumidifier your car might do the same thing.