Disable defroster A/C on a 1998 SE?

Hello,

I recently purchased this 98 Cherokee SE. When I use the defroster, the A/C wants to come on (which I read is normal, under 30F, although it does it at 40F which is another problem), but the A/C cycles several times a minute (a problem I will fix another time).

For right now, I would just like to disable the defrost setting from trying to trigger the A/C.

I pulled the A/C clutch fuse, but the electric fan still comes on (I guess it is expecting the A/C to come on and be operational).

So, is there any way to make it so that the A/C system is not triggered when the defroster is on? Maybe a wire to pull or a sensor to disable?

Thanks for any help with this.

the ac engages to keep the humidity in check .....if you want to disable both the fan and compressor unplug both of them....however depending how warm it gets where you live, while your driving you are most likely going to run hot

You have a vacume leak. Check behind the front bumper on the passanger side. There should be a black ball with a hose running to it. Check there.

VampireJeep said:

You have a vacume leak. Check behind the front bumper on the passanger side. There should be a black ball with a hose running to it. Check there.

Click to expand...

he doesn't have a vaccum leak...the AC is suppose to cycle....

Thanks for all the tips, guys, and I'll check the hose to the round thing tomorrow, just in case. What is that round thing, anyway?

The reason it's cycling so much is you are low on R134a. If it cycles more then 5 times in a minute on high fan coldest setting it's low. Otherwise it's normal. The leak is usually from a bad evaporator core in the heater box, PIA to replace and expensive to have done for you. That black ball behind the bumper is the vacum cannister, without it your heater settings for which vents work, floor, dash, def will go funny and default to defroster output..

http://www.naxja.org/forum/showthread.php?t=930279

This thread should answer your question.

rapid compressor cycleing in cold weather is normal lower temps mean lower pressures meaning the pressures drop to the cutout point more rapidly especially with little or no load on the system

Unplug the connection going to the a/c compressor.

Or unplug the one from the pressure switch. That should kill the fan from coming on as well as the A/C won't want to run with that plug unplugged.

I often thought about rigging up a switch to control the compressor. So perhaps you could have bilevel heat without worrying about the compressor kicking on.

Just a simple switch to either let the compressor run when it should or turn if off completely...

I'll get around to it eventually I assume. Just have to figure out which wire I want to have switched.

Blaine B. said:

Unplug the connection going to the a/c compressor.

Or unplug the one from the pressure switch. That should kill the fan from coming on as well as the A/C won't want to run with that plug unplugged.

I often thought about rigging up a switch to control the compressor. So perhaps you could have bilevel heat without worrying about the compressor kicking on.

Just a simple switch to either let the compressor run when it should or turn if off completely...

I'll get around to it eventually I assume. Just have to figure out which wire I want to have switched.

Click to expand...

I'm guessing the safety switch would be the easiest to do, but I haven't looked at it. Any part of the circuit that grounds would be easiest because you could interrupt the path to ground, and ground the switch locally, needing only one wire for most of the job.

RichP said:

The reason it's cycling so much is you are low on R134a. If it cycles more then 5 times in a minute on high fan coldest setting it's low. Otherwise it's normal. The leak is usually from a bad evaporator core in the heater box, PIA to replace and expensive to have done for you. That black ball behind the bumper is the vacum cannister, without it your heater settings for which vents work, floor, dash, def will go funny and default to defroster output..

Click to expand...

Cool, thanks, Rich, and everyone else here as well. I did pull the cannister "low pressure" thingy, and it's working great now (no AC). I'll play around with the AC (and a switch mod) in awhile, after I do basic tune up stuff first.

Thanks again!