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my aux fan hates me

X

xj_punk

NAXJA Forum User
Location
w jordan utah
so my aux fan decided to stop working and the engine light came on so i checked the relay and swapped other relays and i just can't get it to come on. so i put a jumper wire in the relay's place and it works fine but it would be on all the time if i left it in there so i just watch the temps like a hawk and being in utah winter its not a problem right now anyway.

due to some research and opinions i went and got a temp sensor since they are 16 bucks and installed it and the same thing is going on, the fan will not turn on unless i put a jumper wire in the relay's spot. it also doesn't come on when i turn on the a/c i noticed.

but it gets weird now, i was messing around with the relay and i noticed that if i wiggle it the fan will turn on briefly and so i left the relay in there and moved to the temp sensor connector and i unplugged it and after about 5 sec of it being unplugged the fan turned on and remained on until i plugged it back in... this blows my mind i just don't get it!!!!

i didn't have these probs with my old jeep buggy so any help would be magical, thanks
 
To me that sounds like you may have an electrical issue at the relay connection. You did not mention if you got the engine light checked out or not. If not get it checked out...
 
Its normal for the fan to kick on when you unplug the temp sensor.when you turn the a/c on is the compressor kicking on?For that part of the fan circut to run,the compressor must run also.The temp must get over 225 degrees before the fan runs,so are you sure the engine is running hot enough?
 
1993 4.0

yeah i got cel 35: Cooling fan relay circuit open or shorted

it should be hot enought for the fan to be on, when it worked it would turn on just over 210. it will be a warm weekend so i will keep trying but it is frustrating me...
if i can't get it to work i guess i can wire a switch up and turn it on when i am crawling but i would rather have it work as intended by chryco
 
they are in great shape they look just like the other working relays, i even put a bit of dielectric grease on them and still they don't want to work
 
The presence of dielectric grease is obviously not your problem but note that this grease is an insulator and does not serve to increase electrical conductance. Use something like Ox-Gard for that purpose. The use of dielectric grease around our vehicles is primarily to exclude moisture from connections under the hood.

I have a 93 and had a similar problem a year or so ago except that my fan would always come on when the A/C was on. It would not come on when engine temps rose right up to the red zone and no CEL light. New sensor had no effect. I was obligated to make a weekend trip and didn't have time to mess with it at the time so just added a fan control unit with probe in the radiator. This has worked perfectly since and I just don't think about it except when a thread comes up on the forum.

Your situation does sound more like poor contact somewhere in the PDC if you can get it to come on by moving the relay. I would pursue that as others have suggested. I guess it could be a connection other than one directly associated with the fan relay.
 
Wim, do you have a recommended part number for that relay? Cabin switch just grounds the relay? Thanks!
 
does anyone have a writeup for a switch? the pic helps but i am electrical retarded for the most part. i really wish it would just work but its better to have a switch than nothing
 
Hallo. 2 pics. one for the relay and the other for the fuse by the battery.
Please click. For the switch see earlier pic.of diagram. (click on next)



It is a very nice job to do and it is't difficult. goodluck!

'92 XJ
 
Last edited:
xj_punk said:
does anyone have a writeup for a switch? the pic helps but i am electrical retarded for the most part. i really wish it would just work but its better to have a switch than nothing
Click to expand...

I think you are asking for a diagram of just using a switch without a relay, against everyone's advice. Well, we are here to please, even if it is sometimes against our better judgement. All you have to do is to put the switch in the diagram where the relay is shown and skip the little jumper within the relay circuit. Run one hot wire to inline fuse to switch to wire between PCM and fan. If your switch or whatever melts down, the fuse should still protect you and you can rewire with the relay later. Please don't skip the inline fuse.
 
Great pics that should help xj_punk with his installation, but geez, couldn't you find a host without the picture of the 30 pounds of excess belly fat?! I'm torn between having a beer to help me get the image out of my mind and not having a beer so I don't end up looking like that. Maybe a margarita later....
 
not trying to skip anything, just asking for a writeup of the whole deal... you read me wrong. with the diagram and now the pics i should be able to work it out and thats what i was looking for
 
so i did this tonight and i have a couple questions...

1.i have an illuminated switch and it won't light up, i am guessing this is because no power is going through the switch since it is just connecting to a ground? is there any way to make the switch light up? it has power,acc and ground terminals so i just have it hooked up like that

2. is a diode necessary on the wire between the ecu and fan to keep the power from going back into the ecu when its not supposed to? i know i had to add one when i did the transmission switch mod to keep power from going back into the tcu, thats why i ask.

thanks a million
 
Hallo.
I think you have to draw a new wire from the switched+ wire of the fan into the cabin.
You can use a light or led.on your dash.
If you use a led, there is a need for a resistor.
Use a defused led, because a normal led you can't see it in daylight.



It is possible to use your lighted switch. I think you have to make a bridge by the switch to activate the internal lamp.(depending on the kind)
The wire to ground in the cabin is hot, when the fan is switched on (12 Volt)
No need for a diode, because it's a feedingwire from the ECU to the fanmotor, not a ground switching
 
Last edited:
An illuminated switch should have three wires- ground, power (for the light), and accessory (the switched wire, in this case it would be the wire from your fan relay).
 
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