A/C and electric fan

Now I know there has probably been a thread for this, actually i know there is somewhere. I searched and came up with over 125 threads. My question is what sensor or sensors turn the compressor and the fan on? I had a manual, but lost it when I moved. My A/C worked fine, then one day didn't. I haven't had it for a couple years. Now that it's not my DD I can fix all the little stuff! My fan is wired to a aftermarket relay kit, very shi**y in my opinion. The jeep is a 1991 4.0 5 speed with A/C. Can someone please point me in the right direction? Thanks.

BILL

I wired my fan to a rocker switch mounted in the dash then to an ignition on 12v. I use the double slotted fuse adapter. The stock fuse is still used then it lets me use another fuse for whatever I hook up. It comes on when I turn the key to on or acc. I can still manually turn it off if need be, deep water, engine warm up. Speaking of scary, when I bought my xj all the fuses were 30amp. I guess it was the po answer to blown fuses.

The thing is that I don't want to wire it to a switch. I already have a fan wiring kit that uses a thermostat. I want the computer to control, the way it is stock! And for my A/C to work again, which go hand in hand. SO, if anyone can lend a hand on this one, I would be very grateful. Thanks.


BILL

nwjeeper91 said:

My question is what sensor or sensors turn the compressor and the fan on?

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Check the A/C relay in the main fusebox under the hood. It could be blown.
If your electric fan doesn't turn on when the coolant's above 220*F, the temp. sensor in the t'stat housing has probably gone south.

Dr. Dyno said:

Check the A/C relay in the main fusebox under the hood. It could be blown.
If your electric fan doesn't turn on when the coolant's above 220*F, the temp. sensor in the t'stat housing has probably gone south.

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He said it was an aftermarket kit.
Anyway, 1st we need a little more info.
When you say the AC doesn't work, do you mean puts out warm air? Doesn't put out any air (fan)? What?
Check first to see if the clutch is engaging. If it is then the next suspect is freon.
As for the fan; first jump the thermostat and relay to narrow it down. Just run a couple wires directly from the battery to the fan to see if it works. If not, you know the problem.
Work your way back from there. Put a 12v tester behind the thermostat (check both ways, it could be switching either the pos or the ground).
Then do the same with the relay.

nwjeeper91 said:

Now I know there has probably been a thread for this, actually i know there is somewhere. I searched and came up with over 125 threads. My question is what sensor or sensors turn the compressor and the fan on? I had a manual, but lost it when I moved. My A/C worked fine, then one day didn't. I haven't had it for a couple years. Now that it's not my DD I can fix all the little stuff! My fan is wired to a aftermarket relay kit, very shi**y in my opinion. The jeep is a 1991 4.0 5 speed with A/C. Can someone please point me in the right direction? Thanks.

BILL

Click to expand...

Let me try to explain it.
First The computer don't control the fan in a 91, the fan relay has two input’s that can turn the fan on.
The first input is the fan thermo switch is the lower left of the radiator.
The second input comes from the same wire that turns the compressor clutch on, through a “diode”.
You must use a relay and diode if you want the A/C and the Thermo switch to both be able to control the fan.
If your A/C is low on refrigerant the compressor will not come on and so the fan won’t come on either.
The diode acts as a one way switch so the compressor is not turned on every time your fan is turned on by the thermo switch.

Ok, more info. The clutch on the compressor doesn't engage, the fan works fine when jumped. I don't want to use my aftermarket fan kit. I want the fan to turn on when it is supposed to, hooked to stock wires. So being that the compressor does not engage, yes it blows warm air when the blower motor is on. So even after the a/c quit working I think the fan didn't even turn on if it got warm. One more thing, my reverse lights quit working the same time the fan and a/c quit working. I have since fixed the reverse lights, clever wiring. So I am not worred about the lights. So please no help on that. Right now I am wanting to get the a/c and fan working as they should. Without an aftermarket kit to the fan. Thanks for all the help guys.

BILL

The fan only turns on at 218 deg are you getting that hot? The thermo switch for the fan is in the lower driver side of the radiator.