A/C operation...manual switch.

Hello. I have a 94 sport, 4.0 auto. I have a question about my A/C. Everything works fine with it, but I was wondering about the defroster function. I know that when you turn on the defroster the A/C pump cycles. Is there any way I can interupt the power to the A/C clutch so that it does not come on with the defroster? I just dont see the need for it when Im blowing heat. I realize that it is a good way to keep the system operating in the colder months, but I dont even really use it that often in summer. Will I hurt anything if I put a switch in some place? Our 97 ZJ has a button that turns on/off the A/C...Im not sure if it turns it off on defrost or not tho. Let me know what you all think...or if any of you have done this before. Thanks in advance.

Justin

i forget the exact chemistry of it, but it's got something to do with hot air holding more humidity. you blow hot, humid air on cold glass, and it fogs up worse than before- think of what the mirror in your bathroom looks like after you take a shower. OTOH- hot, dry (which the A/C also does- dries the air) will clear the windshield quicker. the ZJ runs the A/C compressor during defrost regardless of the A/C switch position.

it's possible to bypass (just unplug the wire that energizes the clutch), but i'd leave it as it is.

Cycling the AC every so often also tends to keep the compressor lubed. In the old days, it was not uncommon for the compressor to freeze/rust up over the winter. You can pull the clutch lead on the compressor if you don't want it working.

The AC runs because the cold condenser will cause the humidity in the air to be deposited on the condenser and drain out of the vehicle, just like it does in the summer.. Then when the air is warmed back up, the humidity is considerably lower and will evaporate any condensation on the inside of the window.

ok. thats about what I figured. Thanks for the info. Im going to leave it as it is. Ill just deal with the compressor kicking on and off. Thanks!

Justin

I had the same idea, but wondered if there was a more suitable location upstream of the clutch (relay?) to de-energize manually. I can live without
the AC on defroster function. Any suggestions?

Some systems, newer vw's for sure, only run the compressor when the temperature is above something like above 32 degrees. I'm not ure if jeep uses that thinking.
JoBo

The problem isn't the outside temp, its the inside humidity. The heater recirculates quite a bit of internal air, that's where the humidity comes from, your breath. Thats why when it gets cold the inside of the windows fog up, especially if the heater isn't on.