I have a 2000 F350 with the 7.3. It has 215k with no mods.

I made a stop at the local Kroger this morning and decided to pop the hood and check the oil. When I raised the hood, I heard a hissing sound and narrowed it to the passenger side to the engine compartment.

I noticed the hose going from the back of the AC compressor was dripping condensation. When I felt it it was cold as if the AC had been running.

well it’s in the 50’s here and I was pretty sure I didn’t have the AC on, but checked anyway. As it turned out I was correct, the switch was set on the split between floor and dash and the temp selector was between hot and cold.

I turned the switch to off so neither AC nor heat was in play and drove the same distance home and checked the hose from the AC again. There was no hissing heard, the line was dry and ambient temperature.

I’m ignorant on anything air conditioning related, I admit that, but I’m pretty sure the compressor should not be running while the AC section of the switch isn’t selected.

my question is, where my first jump off point to check? The switch, the compressor? Or are the super duty’s known to have, what I’ll call a hiccup now and then where the AC somehow gets turned on when it isn’t wanted?

 

I believe anytime defrost is on the A/C compressor comes on

 

Well that could get costly with fuel mileage. I guess in winter a guy could unplug the AC compressor so it’s not running all the time.

 

Normal operation. But, not explained in manual. Try Vent or Floor only, shouldn’t engage AC.

Some threads on this over the years. Example:
https://www.ford-trucks.com/forums/1...his-right.html