Auxilliary Fan Over-Ride Switch

I have an auxilliary fan over ride switch that I got from another user a few (maybe 6) years ago. Anyway, it no longer works and I'm hoping for some help (I am stumped).

No recent electrical projects that would have affected the aux. fan. I just noticed one day that it no longer worked.

The switch in the cab still lights ups when switched on so I think it is OK and the relay should be seeing the power. I bought a new relay and swapped it in and the aux. fan still does not come on. The fan does come on with the AC running.

It is a 95 if that matters/helps.

Any ideas? I have a wheeling trip in a few weeks and really need that fan to run all the time.

Thanks

Just because the light on the switch goes on doesn't mean that the switch is 100% working. It would be super easy to check the switch, so that's what I would try next.

Is the relay bypassed when the A/C is on? Do you have a fuse inline for the 12v source to the relay?

Billy

Thanks, I will check the switch next.

Any ideas after the swicth if that is not it?

Kevin said:

Thanks, I will check the switch next.

Any ideas after the swicth if that is not it?

Click to expand...

That depends on the answers to my other questions
Billy

I guess it hekps if I slow down and read more carefully.

I'm not sure if the relay is bypassed when the AC is on. The "system" I bought, plugged into the wiring connection at the aux. fan. I was really impressed with how clean it went in. I wish I coudl remember who I got it from on here. The realy is 40A and 30A depending on status (my replacement relay is 30A/30A).

I'm trying to recall how the wiring is configured. Jeep is at home right now. I do not have a fuse in the power to the relay. I don't think I ended up running power to the fan side of the relay myself. I want to say that the only power I ran was for the switch.

Now I'm just confusing myself.

Found the loose wire. I'm still not sure how this system really works (but it does for now). I had power to the switch to light the switch, but apparently no power to the relay. I don't recall running 2 different power wires, but maybe? Without removing the dash, I won't be able to remember....

A lighted switch gets +12V from a source, and when the switch is "on" it sends it through the light to ground etc. That can all happen even if the switched +12V is not going from the switch to the relay.

Think of it as 2 seperate circuits sharing the same power feed.

I went to the parts store and got a $3 switch and some wire. Then, I hooked up a fused power source to my switch and ran the wiring up under the hood. I hooked that wiring up to a tap I put on the wiring harness for the fan relay. Now, I just flip the switch and on comes the fan. Might be a little more work than a kit, but it's certainly cheaper. Just throwing out another option for the poor people like me.

I just did this mod myself. I didn't use a switch though.

I have searched around and found a few things to note on this topic.

One is that if you diconnect the coolant temp sensor on the thermostat housing it will make the fan come on...it also throws a code but it's a good way to test your system.

Secondly, it is mentioned everywhere that the fan will normally come on when the A/C or defrost is switched on.
This was not the case on my 2001. Nothing made the fan come on in mine...NOTHING.
This could be because my A/C is empty, i'm not sure.

So what I did was, instead of wiring a switch, I found that #86 on the stock relay requires a ground to switch on fan. One of the wires on the top connector to the Drier/Evaporator provides ground when A/C or defrost is on, so I jumpered a wire between that and the #86 wire and now it works just fine. I forgot to make note of the wire colors on my XJ but I think they were both the same color wire.

Now when I turn on A/C or defrost my fan comes on. On other settings it is off. When the ignition is off it is off.

No need for switch or any other parts except a 10" jumper wire...how is that for cheap?

BTW don't cut #86 on the relay...I did this during testing and the engine would not fire.

This is a very interesting thread. I didn't even know about an aux fan switch (neat!) I always thought my aux fan was a nuisance because it comes on every 5 seconds or so when my A/C is on. I always thought it was coming on too frequently, but I don't know.

Kevin said:

Found the loose wire. I'm still not sure how this system really works (but it does for now). I had power to the switch to light the switch, but apparently no power to the relay. I don't recall running 2 different power wires, but maybe? Without removing the dash, I won't be able to remember....

Click to expand...

The whole reason for the relay is so that the switch doesn't have to carry all those amps that the fan/accessory would pull.
Billy

Most switches that light up will have three wires

One to light the light
One to provide power or ground (depending on type of relay)
One to send that power or ground to the relay

alternating how the power flows through will allow control of when the switch light is on

Some light up switches will only have the two wires and will steal a bit of power to light the light without need for extra wire

just turn on the defroster switch. it automatically turns on the fan. that's what i do.