Noob to the site with a noob question...

I just registered here tonight, but I have been lurking for the past couple of weeks.

I have a 1990 XJ Pioneer w/ the 4.0 and I need to install a fan override switch. I plan to take power out of the fuse box, and run a wire from my rocker switch to the orange fan wire in front of the washer fluid reservoir.

My only question I have is, which spot do I plug into on the fuse panel by the pedals? I want it to be hot only when the ignition is in the run position, and of course when my XJ is running.

I'd like to get this done ASAP, so thanks to all who can help!

Should have done a search - heaven knows how many times I've covered this...

Find the thermal fan switch in the driver's side radiator tank - it's a big brass bung with two wires coming out. Use cabling of your choice for this (it's a low-current circuit...) I like to keep a bunch of two- and three-wire rubber-jacketed industrual bulk extension cord around for these jobs...

Use a small-gage wire pair to tap the two wires from the sensor. Run them to a convenient location for a toggle switch somewhere on the panel (I've used either a spot in the shifter console or a blank switch bay on either side of the column) and connect the wires to either side of the switch. Install the switch in a location of your choice.

What you have just done is to wire a switch in parallel (a logical OR setup) with the sensor, and created a third trigger signal for the fan. It will only be hot in RUN, so if you leave the switch on with the key off, the fan will stop. If the switch is turned off, the other two signals (Thermal Fan Switch and A/C Request) will work as normal.

Why do it this way? Simple - it's the easiest solution to the problem. You don't have to pull an extra power lead, and you don't have to wire up another relay. Two wires, a switch, and you're done!

Does it work? I've done it on all three of my Renix XJ's, and it works nicely. Comes in REALLY handy in Bay Area traffic...

5-90

Yes, I actually did do a search, and still do not know the answer to my question.

I know how to run the wires, and how to set the whole thing up. That is not what I'm asking. I want to know where do I put the wire in the fuse box? Which port do I plug it into? it appears that I have three or four open ones.



Thanks

If i may ask why do you want to add the manual switch first thing? You may have a cooling system that needs maintenance. Installing a switch may just cover up a problem.

I think I'd do a cooling system replacement - radiator, hoses, pressure bottle, pressure cap, fan clutch and new coolant. Once you have replaced parts that may be 14 years old and have a over heat problem then consider the switch.

Also if you change the radiator is would be a good time to replace the harmonic balancer. Anytime over 100,000 miles they can fail, much easier to do if the raditor not installed.

I'd also recommend you replace the fan belt and the idle pulley. I am sure the idle pulley bearing is rough and for a $10 pulley it is cheap insurance. You need to get a Kriket II from napa to get the right tension on the new belt.

My advice is to make sure the cooling system is working 100% before you begin to modify.

I own a 88 XJ which is basically idential to your 90 XJ. You can turn on the electric fan by just running the AC. Everytime the clutch engages on the AC compressor the electric fan runs. It does not run 100% of the time but it does when the compressor is engaged. Also if you are running hot that may help get heat out of the engine. there also the old trusted second radiator you can use, turn on the heat and turn the fan to high speed to get heat out of the coolant.

martin said:

If i may ask why do you want to add the manual switch first thing? You may have a cooling system that needs maintenance. Installing a switch may just cover up a problem.

I think I'd do a cooling system replacement - radiator, hoses, pressure bottle, pressure cap, fan clutch and new coolant. Once you have replaced parts that may be 14 years old and have a over heat problem then consider the switch.

Also if you change the radiator is would be a good time to replace the harmonic balancer. Anytime over 100,000 miles they can fail, much easier to do if the raditor not installed.

I'd also recommend you replace the fan belt and the idle pulley. I am sure the idle pulley bearing is rough and for a $10 pulley it is cheap insurance. You need to get a Kriket II from napa to get the right tension on the new belt.

My advice is to make sure the cooling system is working 100% before you begin to modify.

I own a 88 XJ which is basically idential to your 90 XJ. You can turn on the electric fan by just running the AC. Everytime the clutch engages on the AC compressor the electric fan runs. It does not run 100% of the time but it does when the compressor is engaged. Also if you are running hot that may help get heat out of the engine. there also the old trusted second radiator you can use, turn on the heat and turn the fan to high speed to get heat out of the coolant.

Click to expand...

The cooling system is in good condition. I've got a new radiator, water pump, thermostat, bottle, and cap. It normally runs great and keeps itself under 210. Only it's getting hot here in the summer, and at idle during traffic it likes to start heating up. I know the fan will come on with AC, but I don't like to run it all the time.

That's the beauty of the mod as I gave it to you - you only need the two wires. No touching the fuze box, no figuring anything out - you just wire a switch in parallel and it's sorted. Why make a simple job difficult?

I did somehting ismilar to a work truck a couple jobs ago - my boss told me he needed something like four diodes and a couple resistor to get the fuel preheater working, and I did it with a six-inch wire. Still works - and it's been five years!

Trust me, don't make things difficult for yourself. Fuze box wiring is a pain, and you're working with something that already has a power circuit set up, so just use that.

5-90

I'll still need to ground the switch, correct? It has a light..

90Pioneer said:

I'll still need to ground the switch, correct? It has a light..

Click to expand...

If you are using a lighted switch, then you will need to run a third wire to ground. That was not part of your original question. The ground wire can run to any bolt or screw under the dash that's attached into the body/chassis.

Are you now clear on how to wire it as 5-90 described? That is by far the best and easiest way to wire this mod on an -87 - '90 XJ.

90Pioneer, I looked at the list of stuff you have done and a new fan clutch is NOT listed. Is this an omission or you still have an old one on the engine?

Before the summer heat comes I recommend you install a new mechanical fan clutch. There not know accurate way to test the fan clutch and have a service life of 5 years at most. When you do change the fan clutch take in the old one to the parts store and match it up. Some aftermarket clutches are too big and would would require tilting the radiator to install.

Also if you do wire up the manual fan switch you may be trying to figure out where to place the switch. There are locatons for 4 switches below the speedometer cluster. My XJ does not have fog lamps but it has the opening with a cover over it. If you have blank over one of these switch locations then install the switch there:
1) fog lights
2) Rear wiper
3) Rear Defrost

If you go with the location I suggest go to your dealer and buy a fog light switch. It is a single pole/single throw switch. It also has an indicator light. There are 3 terminals on the back - Hot, return and ground. The ground only used for the indicator lamp. I did get a switch from NAPA, I found it on their web site and ordered at my local store. I also found the flog light switch on rockauto.com. I then checked my dealer and they had it on the shelf.

I still suggest to replace the fan clutch before you do any wiring modifications.