Radiator Fan Override Switch (The Easy Way)

[MrSimon]

Here is the switch I'm using.

I have #6 hooked to the dash lights and #7 grounded. This works great for the lower light on the switch. It comes on with the dash lights and dims nicely. No problems there.

I am feeding a ground signal to #2 and #3 goes to the fan relay I installed.

The switch works the fan exactly as it should with no problems.

If I ground #8, then the top (larger) light on the switch is on all the time and GOES OUT when I turn the switch on. It's like the fan relay is back feeding a 12v signal to the switch when the the switch is in the off position.

Any thoughts? I'd like the top light to come on with the fan and go off with the fan.

 

[mechbullxj]

Try connecting #2 to your relay and #3 to the fuse.:dunno: At your own risk.

 

[fyrfytr1717]

mechbull... please stop. Guessing at electrical and offering it up as advice only causes confusion and quite possibly damage/fire.

MrSimon, connect the dots... According to your diagram, there are two individual circuits in your switch. The circles with the "X" in the middle are your bulbs and need (+) on one side and (-) on the other in order for those electrons to flow through your bulbs.

1. The dash light circuit begins with (-) on pin 7, passes through the bulb, and ends with (+) on pin 6. You currently have that wired according to the diagram.

2. The indicator light circuit in our application is reversed. We need to apply (-) to pin 2 so that pin 3 receives a ground signal when the switch is activated. Since pin 2 is (-) and passes this (-) on to pin 3 when the switch is activated, pin 8 needs to be (+) in order to complete the circuit.

Two possible issues. First, as I mentioned previously, if the switch uses an LED for the indicator this will not work as current only flows through them one direction. Second, if (despite what the drawing shows) pin 7 & 8 are actually a common (shared) ground for both lights, this will not work as desired. Do a continuity test between pin 7 & 8 to find out.

 

[mechbullxj]

Yes, don't guess when doing electrical work. Should Mr. Simon switch #2 and #3 on the switch, a fuse could be blown, or circuit breaker tripped. If it did happen to ruin the switch he'd be able to start over. Buy a new switch, one that doesn't offer up a confusing wiring scheme.:dunno: 4 amps to your relay. At your own risk.

 

[MrSimon]

mechbull... please stop. Guessing at electrical and offering it up as advice only causes confusion and quite possibly damage/fire.

MrSimon, connect the dots... According to your diagram, there are two individual circuits in your switch. The circles with the "X" in the middle are your bulbs and need (+) on one side and (-) on the other in order for those electrons to flow through your bulbs.

1. The dash light circuit begins with (-) on pin 7, passes through the bulb, and ends with (+) on pin 6. You currently have that wired according to the diagram.

2. The indicator light circuit in our application is reversed. We need to apply (-) to pin 2 so that pin 3 receives a ground signal when the switch is activated. Since pin 2 is (-) and passes this (-) on to pin 3 when the switch is activated, pin 8 needs to be (+) in order to complete the circuit.

Two possible issues. First, as I mentioned previously, if the switch uses an LED for the indicator this will not work as current only flows through them one direction. Second, if (despite what the drawing shows) pin 7 & 8 are actually a common (shared) ground for both lights, this will not work as desired. Do a continuity test between pin 7 & 8 to find out.

For the indicator light circuit, if the light is coming on when the switch is in the off position, there must be a + signal coming from somewhere, right? And it can only be coming from the new fan relay that I installed according to the original instructions in this thread. Is that normal?

If it is normal, and I feed a + signal to the #8 pin, won't I have two + signals coming in from different sides of the same circuit?

 

[fyrfytr1717]

The stray 12V+ is likely coming from the factory relay. When the ignition is on, 12V+ is being fed to one side of the factory relay's coil. It is just waiting for the other side of the coil to be grounded in order to activate.

My question would be why does the same ground that is completing the indicator light circuit not also cause the factory relay to activate? Hard to know what exactly the wiring inside the switch looks like so far as circuit isolation and/or multiple contacts goes.

Regardless, 12V+ coming to the bulb from both sides won't do anything as the circuit has no potential. When you flip the switch, pin 3 providing 12V- in place of that stray 12V+ should cause the light to turn on.

 

[hubs97xj]

I have deleted the images from pbucket, so hopefully it won't get dug up much more. We're obviously years from being able to edit the posts, so sorry if it's still raining on your parade. My intention was to correct the bad info I was finding, and offer an alternative method to skin the same cat as easily. Cheers.

 

[fyrfytr1717]

No worries hubs, your posts have been more than helpful over the many years you've been part of . It was a perfectly acceptable wiring diagram that you posted, it's just that in this particular thread, it was confusing folks who were just skimming through and not viewing it in context. Tons of threads on here discussing the approach you drew up of which I'm hoping your now deleted picture wasn't an integral part of.

 

[craigbhikin]

Thanks, you idea sounds better than my idea of just splicing a switch in with power and fuse. I will need to re read it again to be sure of what I am doing.

 

[rixdafix]

Great 6 year old write that's still helping people and inspired my first post. Did my 01 today. This mod works like a charm. I actually accessed most of the wires from inside the underneath of the distribution center. All solder and heat-shrink. Even used a switch with an LED indicator by disassembling the switch, reversing the diode leads and connecting the switches outer terminals reversed. Works like a charm. Thanks again.

 

[fyrfytr1717]

Glad you found it helpful rixdafix, and strong work with re-rengineering your LED switch to work!

 

[Coach Bruce]

Great 6 year old write that's still helping people and inspired my first post. Did my 01 today. This mod works like a charm. I actually accessed most of the wires from inside the underneath of the distribution center. All solder and heat-shrink. Even used a switch with an LED indicator by disassembling the switch, reversing the diode leads and connecting the switches outer terminals reversed. Works like a charm. Thanks again.

I'm doing this mod today and couldn't figure out a way to get the led switch to light properly and send a neg. signal so I was going to use a second relay to switch the signal polarity under the hood. Can you explain how you modified the switch? I'm using a Carline switch from OTRATTW.
It has an independent LED for the text and a dependent LED for the symbol when activated. Any help would be appreciated.

 

[3blackbirds]

I'm going to resurrect this thread, hopefully. I have a '99 with the aux fan switch wired to the battery because I got a CEL. Switch works great, but getting heat soak. Photobucket has updated their policies so I can't see the diagrams anymore on how to add in the ELK-960 timer. Can anyone provide the diagrams for the ELK-960? -Thanks

 

[IslanderOffRoad]

now that editing is allowed, any chance we could get the photos back?

This is on my to do list, as my XJ heat soaks pretty bad when wheeling. Leaving the aux fan running when I do a short trail shut-off would help.

 

[josh9mile]

I did this to both my jeeps by splicing a wire into the dark blue/pink wire with just a switch to ground. No CEL yet and it was super easy!

 

[IslanderOffRoad]

I did this to both my jeeps by splicing a wire into the dark blue/pink wire with just a switch to ground. No CEL yet and it was super easy!

What year?

 

[josh9mile]

93 and 96

 

[lazyxj]

This is on my to do list, as my XJ heat soaks pretty bad when wheeling. Leaving the aux fan running when I do a short trail shut-off would help.

My 01 had always had this problem when wheeling in warm conditions, even after a long list of mods designed to prevent it.
The best cure so far has been adding a 3 minute timer to the aux fan so it continues to run after the engine is shut down. Pushing a button on the console starts the timer.
Works every time and is well tested with nine years of use.

https://www.flickr.com/photos/lwade/sets/72157617434915718/with/3482846101/

 

[kastein]

93 and 96

Both of those are before the OBD-2 failure detection system really grew teeth (and the 93 is before OBD-2 even existed.) So that's not surprising. This writeup is really intended for 97-01 guys whose ECUs will freak out if they see a solenoid/relay drive circuit stuck high or low when it shouldn't be.

Kinda surprised you got away with it on the 96, but not overly. 96 OBD-2 failure detection was extremely minimal compared with even 97s, and they really added a lot for 98.

 

[josh9mile]

Both of those are before the OBD-2 failure detection system really grew teeth (and the 93 is before OBD-2 even existed.) So that's not surprising. This writeup is really intended for 97-01 guys whose ECUs will freak out if they see a solenoid/relay drive circuit stuck high or low when it shouldn't be.

Kinda surprised you got away with it on the 96, but not overly. 96 OBD-2 failure detection was extremely minimal compared with even 97s, and they really added a lot for 98.

Actually just tonight I got a CEL for fan relay. Thought I was gonna be lucky.