I have a '95 Ranger 2wd, 4 cyl. When I turned on the defroster the fan belt screeched so I shut it off and after investigating found that the AC compressor is locked up. I haven't used the AC for about a year and a half. I am not questioning why the compressor went bad. My question is why does the AC clutch engage when the defroster is turned on? In the past the only time the AC went on is when I turned the knob to AC or AC max.
I'm pretty sure with out trucks the AC comes on with all settings minus the all head setting or all feet setting. Everything else it comes on.
Not sure about your year (probably the same) but on my 2001 there was a thread here that you can wire in a toggle switch to the purple wire in the HVAC controls and then you can manually turn on/off the AC compressor. I do this all the time.. IE: in the winter time I don't want the AC on when I have heat coming out so it's just heat.
I think the point of the AC coming on with defrost is to minimize condensation.
-Nigel
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2001 Ranger XLT 2.3L Auto: Bunch of misc mods.
Little lift: 4" Spindle Lift w/ 2" shackles and 2" oem blocks.OEM Ranger Sport Wheels: Tires=245x75x16
The A/C compressor runs in defrost and that is normal. The defrost runs like this to keep the windshield from fogging up in winter, fall, spring, and summer.