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With the factory Ext Idle switch being so elusive, I thought that there must be a way to enable the functionality and make it look factory, but without spending a mint on eBay for an original switch. So, Ralph77 graciously sent me a picture of the circuit board of the Ext Idle, and off I went a searching. I knew the fog light switch had a different circuit board, the wiper had too many wires, and the defroster was a momentary, but I had never looked at the circuit boards, just the mechanics. Once I started digging in to these, I also remembered my Dad had an O/D OFF switch in his TJ. After comparing the schematic in the TJ FSM vs the XJ Ext Idle, I decided that the functions were very similar, so I grabbed a switch/pigtail from eBay to investigate that circuitry as well. I found that it was VERY similar to the Extended Idle. In fact, the pigtail was keyed exactly like the Ext Idle, and the same pins were used for this very similar application, but different color wires were used.

Upon further inspection, I found that three of these switches (the Extended Idle, Defroster, and OD/OFF) shared the same basic design of the circuit board. This allowed them to reuse the same basic design for multiple applications. They simply modified the circuit board for a specific purpose by cutting the traces to re-route the electrical signal to different a path. During the injection molding process for each application/part number, certain traces are severed/punched and melted plastic fills the void to prevent them ever connecting again. Also, for each different application a plug is keyed to match. Pretty cool and ingenious.

This got me thinking that I could actually use either one of these (defroster or O/D OFF) for an Extended Idle with a little modification. The cheapest option and most readily available of the two is the Defroster switch, so I chose that one for my test. Note that both the Defroster and O/D OFF are mechanically and electrically the same, the only physical differences being the label, differently keyed pigtails and the matching keyed casings.

In comparison to the Extended Idle, electrically there are only two very minor differences on the Ext Idle circuit board. This enables the connection to on Pin 3 to ground, which enables the EXT Idle and allows the "on" indicator light to function properly. This is somewhat reverse logic because normally you would want positive voltage on that pin to send to an accessory or relay, not negative. Also, the only mechanical difference was that it wasn't a momentary switch. This seemed pretty easy to do, so I continued on with the research.

To make it look factory, I knew I would want a new bezel. Since the 4 position bezels are as rare as unicorns, I ordered an aftermarket panel from I found the listing and contacted him over eBay messaging, but found that both his website and his Etsy stores offered USB and power options for very reasonable prices. Jonathan is the owner, was nice as can be, and even shipped it to me while he was on holiday in CA with lightning speed. He lists the Police Package 4 switch bezel for $28, and even offers multiple options for the power outlets including USB ports, also at a reasonable cost. Product picture from his website is below, and was listed at $38 as pictured below (at the time of this writing):


Now I bet right about now you are saying, OK great. How much is all this going to cost? For me was just under $50, because I already had an extra XJ defroster switch/pigtail, but even with the TJ O/D OFF switch (ironically pictured above) it still would have been cheap. I picked it up on eBay for $20. You can pick either one up for ~$10-$20 on eBay or even cheaper at a pick-n-pull. Add $28 for a bezel and another $17 for the cheap-properly-named-but-not-quite-as-good-as-factory toggle and your total cost should still be under $60-$70 bucks. That's as close to factory as you can get for that price!

For my install I opted for the panel that included 6 OEM switches (still only $28!) because I plan on adding switches for other accessories, and I don't really need two power ports up front. I installed a Dual USB charging port with Volt meter I had ordered from Amazon and was leftover from my pop-up camper install. After seeing Ralph77's "rear fog" switch, I had to find one too, but mine's not stock. Sniff. sniff. Looked forever. Couldn't find it...... below were while testing fitment on the new panel, so nothing new was hooked up yet, I just moved my three factory switches over and did wire the USB from the factory Passenger Power Point circuit. Eventually I plan on relocating the second XJ power outlet circuit to the rear of the console in the back ash tray spot with another USB charging port.



If this sounds interesting, affordable, and do-able with your current skill set, then read on adventurous adventurer!

To make either the Defroster or O/D OFF switches function as an Extended idle, here are the modifications that will need to be made.

1. Modify the switch mechanics.

The momentary switches contain a spring and white plunger on the internal mechanism to prevent full time circuit engagement. If you remove the plunger and spring from the top of the internal mechanism, they are then mechanically the same as an on/off switch. To modify the mechanism, obtain either switch and:

a. Remove the lights from the top and bottom of the switch with a simple quarter turn counter clockwise with a small flat head screwdriver. Set aside, you’ll reinstall them later.

b. Remove the circuit board by releasing the tabs on top and bottom with a flathead screwdriver. Once the clips are freed, pull apart slowly. I find that this works best to orient the switch with the toggle on the bottom, circuit board on top, then pull up on the circuit board. The internals stay internal.

c. GENTLY remove the internal mechanism. Then remove the plunger and spring on the top of that mechanism. If you wanna have some fun, just push it down and slide your finger to the side. It’ll remove itself… AND disappear…. At incredible speed…. Have fun searching for it. I did…. If you lead a predictable and boring life, just pull on it gently and it’ll come loose…


The other plunger must remain in the switch to operate properly.

2. Modify the Circuits
Disclaimer: Do this at your own risk.
I am not an electrician, I'm a hobbyist, and a novice, but mechanically inclined super geek that likes to tinker with stuff. This is what worked for me with the mods I made, and I'm not responsible for your eventual outcome, although I don't see how it could possibly go wrong if instructions below are followed. This is simply rerouting the path to a GROUND, but I'll say it again, do this at your own risk.

Now that's over, the original Ext Idle, O/D OFF, and Defroster Circuit boards are below, labeled above each. These are oriented with pins south. On the O/D OFF or Defroster circuit boards only two simple mods are required, and this is only to allow the "on" light functionality: simply cut a trace, and connect a trace as seen below.

Note that even with no circuit modifications, either of these switches will still engage the extended idle function because the switch will mechanically engage the ground to the PCM just like the Ext Idle. Panel illumination and dimmer functions will function correctly when the headlights are on, however, the "on" indicator light will always be lit regardless of the switch position. This is because the ground connection is always direct and will not be controlled by the switch. This is why the circuit traces must be modified.


Make sure the cut on the left trace is above where the internal mechanism slides up to make the ground connection, use the above pictures for examples. You can see where the internal mechanism rubs the traces and makes contact. Again, cut the trace somewhere above that. Here’s my modded defroster internals:


Using the right Dremel bit could have made the cut on the left trace a little cleaner. I didn’t have my glasses and I thought the Dremel bit I picked was a cutter. It was not. Second bit was.

I used a soldering iron and solder to connect the trace, but it was very difficult to get the solder to adhere to the traces; I had to rough up the traces with Dremel bit to get it to adhere. The only fallout of a connection failure on this trace is that the “on” indicator light will not function properly. It will still engage the ground to the PCM. Testing after putting it back together will verify functionality. See below instructions. Also note that this cannot be just a big-ol’-glob-o’-solder. The internal mechanism will slide up adjacent to this solder point, so it can possibly come into contact with the solder and break it loose. Think small, solder small, and TEST afterwards. There’s a reason I know this….

If I had it to do over again (for the fourth time). I’d probably drill a small hole on each side and run a small strand of copper wire through each, then solder the wires and clip excess off the back. You know, like on a real circuit board. Normally I wouldn’t dream of doing that, but since it is a ground connection anyway it’s not a big deal.... there’s nothing to short out. I also thought that a tiny, short screw would provide the same/better connectivity, but I didn’t have any.

After the circuit board is modified, then reassemble switch. At this point it can be tested with the Defroster Toggle, or replace the toggle so it looks purdy, and then test.

3. Replace the Defroster Toggle with Ext Idle Toggle

a. Carefully remove the Defroster or O/D OFF toggle by using a screwdriver on the sides to pry it apart enough to remove the toggle.

b. Remove the EXT IDLE toggle using the same method.

Note that one of the nubs on the side of the EXT IDLE toggle will be bigger than the hole on the defroster switch housing, so you will have to ream it out slightly to make it fit. Take your time and do it right so it’s not sloppy. Once that’s done, pop in the EXT IDLE toggle into the Defroster switch housing.

4. Test functionality of your connections.
If everything works just as it should, the dimmer circuit illuminates and dims the “EXT IDLE” just like the other switches, and when the switch is engaged, the orange light is illuminated and the high idle is engaged. Testing procedure below.

a. Make your Connections: Ground to pin one. Put 12v+ power to pins 3&4. Words EXT IDLE on the toggle should be lit. All of these pins are non modified circuits, so if they don’t work, it is most likely a bulb. Also verify that pin 2 has no continuity to ground.


b. Move switch to on position. Indicator light should illuminate. This is one of the modified circuits, if not lit, check solder joint or connection of traces that were connected. If at first you don’ succeed, try, try again. Check bulb too, mine was bad. Also verify that pin 2 has continuity to ground.


c. Move switch to off position. Indicator light should not be illuminated. Verify that pin 2 has no continuity to ground.

d. Slap yourself on the back for a job well done.

I did create a short video to show how the connections and test should go, link is here.


5. Last step is to wire up the pigtail as shown below based on the switch you chose. All three of these plugs match pin 1 and 4, but have different color wires on the pigtails for pins 2 & 3.

PinFunctionExtended Idle PigtailTJ O/D OFF PigtailDefroster Pigtail
2Idle Actuator (A12 on PCM connector)GreyOrange w/White StripeDk Blue w/White Stripe**
3Fused IgnitionDk Blue w/White Stripe*Green w/Lt Blue StripeLt Blue w/Yellow Stripe
4Fused Panel Lamps Dimmer Switch SignalOrangeOrangeOrange

  • * More information on this Fused Ignition Dk Blue w/White Stripe from this NAXJA thread, post 149 point 3. In my 1998 XJ Sport, this harness was not In use at all, I found it taped to the radio harness behind the thermostat control panel. I used this source for both pin 1 and 3 since it already had both ground and power. For Pin 4 I simply tapped the dimmer wire on Fog plug, (Orange in color). Pin 2 is the Idle Actuator wire, which has been really well covered under other threads. Connect to the solid grey wire at pin A12 on the PCM connector. I got super lucky. In my 1998 XJ Sport, this was extended past C107 and into the cab, I simply toned it out using a Harbor Freight wire tracer/toner and tapped into it at the closest place. It was booger to find and get at, but it was already there, so I used it.
  • ** The wire on the factory Defroster pigtail Pin 2 is Dk Blue w/White stripe. When testing the defroster pigtail I opted to have the wires match so I swapped 2 & 3 on the defroster pigtail using a pin extractor so that the only wiring color difference from the factory Ext Idle pigtail would be the Idle Actuator wire, see picture below. Hope that's not confusing.
  • If you wanted to drop an extra ~$40 you could get an actual OEM IDLE pigtail, Part Number - 68057305AA to use with the O/D OFF switch. Don't know why anyone would want to, but hey, you could.… and the keyed plug will match up.
My switch after modifications is pictured below (before I wired it all in):


Note Pin 2 & 3 on my pigtail is swapped so that it will match up with the Dk Blue w/ White Stripe.

So, this adds another option to the arsenal of switches that can be used to accomplish a factory looking extended idle. This one is super affordable and pretty simple. So congratulate yourself for cheating that seller on eBay that was asking way too much for a legit EXT IDLE outta your cold hard earned cashola. Take the rest of the money you just saved by switching (no pun intended) to a more economical method for Extended Idling, and put it toward a night out with your significant other. In my case, I don't have one of those so I spent it on my four adopted kids, since they did help me tinker with it.

Seriously though, what prompted me on this was the challenge of finding a less expensive alternative. Happy Extended Idling!


1,264 Posts
Discussion Starter · #43 ·
All I can say is WOWSERS!!! That is the most comprehensive modification to result in an EXT IDLE switch I have seen ever. KUDOS! I especially like that you understand that is a matter of simply grounding the A-12 wire that enables the EXT IDLE. Everything else is just making it look and function like stock but at a reasonable effort and price. As for me, I am much too old and clumsy to even attempt that. I had a rear washer switch apart once and besides the springs flying past my head, the little parts inside were way too delicate for this old clod to fool with. But these younger guys should be up to it.

Premium Member
11 Posts
I finally found the pictures of the electrical connector where the A12 grey wire terminated inside the cab. I knew I took them, but evidently they were accidentally "deleted", I found them in that folder anyway.

There are two plugs located just above the driver's kick panel, the A12 wire was terminated on the block closest to the firewall, and was located in the position where the negative lead to the meter is pointing. I removed the front side plug to confirm the position in the connector.

Telephone Office equipment Telephony Gas Audio equipment

I didn't have anything that would plug in, so I tapped it behind the block, then extended that wire to the switch. For my modified defroster switch with pins 2&3 reversed, this connected to the Lt Blue w/ Yellow Stripe.

Electrical wiring Cable Wire Electrical supply Fiber

Worked like a charm. Like I said, it was a booger to find and get to, but worked really well. Less than 2 feet of wire to actually run!

1,264 Posts
Discussion Starter · #46 ·
UPDATE: I found out that the idle WILL try and sit at 1000rpm even in gear if you wire it the way I did. It falters a bit because of the drag of the transmission. But it will go back to 1000 rpm as soon as it can, even in gear. I guess the computer is not used to doing this and is getting confused. By grounding the NSS wire it is being told it is in P or N, but then it is seeing the speedometer register movement. But the EXT is trying to over-ride that. It works.
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