AC bypass switch?

Okay so listen up you second gen XJ owners, you know how you cant use heat on the face/feet mode without running the compressor? And also (whether you noticed or not) even though the face/defrost mode is in white it still turns the compressor on? I dont know about you but id rather not use that gas unless i am getting some balls to the wall cold a/c, so for when i want to use heat to defrost (yes this does work, you have to use AC at first though obviously...) or even feet/face heat can i make a small switch to run to some line on the compressor that just makes connects a wire through the switch? if so which one? Im thikning a smaller one so that i dont damage the switch or over heat it... I know there are other wasy to do this (take apart switch panel, solder the connections, no thanks),but has any one tried this?

i think id try to operate the relay but if thats a pain than im sure you could break the wire powering the compressor i did it on a toyota years ago with no probs i just used one of those cheap rocker switchs

Not worth the effort in my opinion. You're going to spend more on the supplies to make it work than you will with fuel savings. I'd say it's a safe bet that you won't notice any gains in milage if you were to do this.

There is no face/defrost mode on my 97, but I think I know what you're getting at. The reason the compressor runs is because it removes moisture from the air, which greatly improves the defrost (defogging, actually) effect. Yes, you can use just hot air, but it's not as useful. The reason you have condensation on the windows in the first place is moisture in the air. Blowing more warm moist air against cold glass isn't all that great, and the savings in fuel, compared the damage you're going to cause attempting this, is going to be negligible.

feet/defrost, my bad..


Cold air works good at first, but once its all gone heat works just as well, at least in my application. And yes, AC does make a significant difference, in my moms car its about 2 miles per gallon. Plus my belt squeeks sometimes when i use AC. If i did run this switch to the power cable on the compressor, it would have to be a pretty big ass switch im guessing?

As for AC on this jeep, ive owned it for a year, and on my last one i noticed this too, it does use more gas with the AC on. Yours may not, but mine sure as hell does. Im not asking if you guys think this is a good idea im asking how?

Im thinking you can run like a relay i think thats what its called, so that the intense power of the power cable for the compressor wont burn out the switch...?

emr1101 said:

feet/defrost, my bad..


Cold air works good at first, but once its all gone heat works just as well, at least in my application. And yes, AC does make a significant difference, in my moms car its about 2 miles per gallon. Plus my belt squeeks sometimes when i use AC. If i did run this switch to the power cable on the compressor, it would have to be a pretty big ass switch im guessing?

As for AC on this jeep, ive owned it for a year, and on my last one i noticed this too, it does use more gas with the AC on. Yours may not, but mine sure as hell does. Im not asking if you guys think this is a good idea im asking how?

Im thinking you can run like a relay i think thats what its called, so that the intense power of the power cable for the compressor wont burn out the switch...?

Click to expand...

The compressor uses a lot of engine power, but the clutch doesn't use that much electrical. You can run a clutch through a small toggle no prob. IIRC, it's less than 10 amps to engage an a/c clutch.

You could also just disconnect the clutch connector through the winter months as you won't be needing a/c anyway.

Funny.
I just did something like this yesterday for completely different reasons.

To have control of acc. fan and raise idle (1000RPM) for off road applications.
I'm thinking little harder to stall since it isn't trying to return to 750RPM

Voltage at connection seems to be full current -/+ 1v
If someone has an ammeter to test amperage should give definite answer.

relays aren't hard to run, or just disconnect the A/C clutch and you're set.
Easy to reconnect. <1min.

Oh I didnt even know there was a difference between the clutch engaging and the compressor running, I mean the clutch is what is electrically powered and that is what engages the compressor so i should just add a relay to that connection somewhere along the line?

the compressor runs when the clutch engages. if you break the power there it will just freewheel the clutch

Exactly. If the clutch is engaged the compressor is running.

so disabling power to the clutch is the goal then?

Correct. I simply unplug mine during the winter months.