How To Rebuild/Recondition Headlight/Dimmer Switch (97+)

[NW99XJ]

Are your dash lights flickering? Or have they stopped working?
Maybe your ability to dim them is gone altogether....
This may take care of your problems.
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NOTE: It's always a good idea to do some simple trouble shooting before tearing into and disassembling things. CHECK YOUR FUSES.
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This is a pretty simple process and can be done in a short period of time for someone familiar with taking things apart. No special tools are required, but having a decent selection of screw drivers is a good idea, and you may want to have a third hand around to help you at one point.
You'll also want to grab some Scotch Brite - we'll use this later.
-The first step is to get to the switch, we cant do this with it in the dash.
If you are afraid of draining your battery trying to do this (as your lights will be on until you disconnect the switch) you may opt to disconnect your battery before getting started.
-First remove the knee panel - this is the part that's below the steering column. There's three screws on the bottom that hold the plastic on, and two spring clips at the top. This will expose the steel knee guard. Two screws will remove this. This will give us access to the back of the switch.
-Next is to remove the plunger, this is the part that you actually pull/push on to turn the lights on off. There is a button that is on the right side of the switch, reach up into the dash and push on this little button.




Its spring loaded, and acts as a keeper to prevent the switch's plunger from coming out of the dash when you pull on it. It may take some wiggling and finagling to get it to happen, and you MAY need to pull kind of hard, it may also help to do it in stages, mine took holding the button down, pulling the plunger, releasing the button pulling again, pushing the button, and pulling a couple more times. The rod of the switch is triangular so it may require you to turn it back and forth while you pull it.
-Once the plunger is out, you'll need to unscrew the threaded nut that holds the switch onto the dash. This can be done in most cases with your fingers, but its designed in such a way that a larger flat head screw driver, or a set of pliers will work as well. Several turns and the switch is loose and out.

(NOTE: in this pic you'll see that the upper portion of the dash trim is removed, it is not necessary to do so for this job, I had it off to do other things at the same time - replacing instrument cluster lights.)
Disconnect the main harness and the smaller secondary harness (two black wires) from the switch housing. You're now ready to start the rebuild.

The switch is a rotating assembly that uses a stationary contact to complete a circuit through a series of contacts on a disc.
Over time debris builds up on or around the contacts, and the contacts themselves will oxidize and corrode. This of course limits or prevents continuity, and will present problems such as dimming your dash lights, or having "dead spots" in the switch when trying to do so, etc....
Here's a closer look at the disk and its contact patches. This is looking at it from the right side of the switch, you'll notice the little detent button that locks the plunger into the switch here again.


Here we see the main stationary contact arm that engages the contacts on the rotating disc. (I'm pointing at it with a pick tool in the next two pictures.) You'll also see a buildup of dust and lint.

 

[NW99XJ]

Dis-assembly is pretty straight forward, all the pieces (except for the main switch body itself) are held in place by spring pressure. It may look intimidating but all the parts are keyed - meaning you cant put them back together wrong. Just remember the order, and orientation, and you'll do fine. Here's a pic and list for reference as to the order of the assembly
- The names of these are just for descriptive purposes only, and are just for reference.

From left to right--> Switch Body --> Copper Ring --> Contact Disk --> Metal Shroud --> Spring --> Secondary Contact Plate --> Plastic Isolator/Spacer.

To Disassemble the switch you'll need to push everything from the disk towards the plastic isolator. (away from the switch) This is where a third hand may come in useful. This gives you some room (not much - but enough) to remove the copper ring. It should just fall out. This in turn will give you much more room to move the disk and everything else back towards the switch body to remove it from the housing. Lay it all out in order like I did to help you remember how it all goes back together.
-Next up we'll want to clean and recondition everything up.
The heart of the switch is the contact disc, here you can see it sees a lot of abuse and (in my case) is in pretty bad condition.




Clean the disc with rubbing alcohol and a clean rag/paper towell, DO NOT use any harsh abrasives, scouring pads, or caustic chemicals here. The alcohol is just to remove most of the gunk that is built up on the surface. Next you'll want to CAREFULLY remove the oxidation from the contacts These are the metal patches on the disk. I used a small piece of Scotch-Brite but a scrubby pad may work as well.... Once done give it another wipe down with alcohol to remove any oxidation dust/debris that you created.
DO NOT USE STEEL WOOL OR A FILE! ...and here's why.
The darker areas (circled in red) between the metal contact patches are actually resistor plates and can be damaged if you go crazy on this thing with something very abrasive. Try to avoid rubbing these with the Scotch-Brite.

You'll notice, if you go around the disc (in these pics its all cleaned up) with a DMM (Volt Meter) you can see the changes in resistance from the center contact to the various others around the perimeter of the disc. These are the contacts that the stationary arm touches as you rotate your knob to dim/brighten your dash lights. The voltage passes thru these various contacts and the voltage sent to your dash lights changes due to the different level of resistance.






Next up clean the contacts on the switch itself:


Be gentle with the stationary arm... its not rock solid, you don't want to bend this too much out of alignment, but before you put everything back together, you may opt to bend this a little further towards the disk, to ensure a good contact in the future.
Before reassembling everything, clean the brass ring real good as well. Mine had a nice build-up of gunk where it contacts the switch body.

Scotch-brite came in handy for this part too - wipe it down with alcohol after scrubbing.
Good As New:


Clean the secondary contact plate as you did everything else.
Put it all back together in your hand in the order it came out.
Oddly enough, putting it all back into the switch is WAY easier than it was getting it out. Put the ring, the disk, the shroud, the spring, the secondary contact plate, and the isolator, back into the switch housing as one whole compressed assembly. It should just pop right in.
Plug the harness' back into the switch, and re-install the switch into the dash in the reverse order of taking it out.
NOTE: you may opt to test your switch before re-installing it, just to make sure you didn't mess something up. Push the plunger back into the switch until it bottoms out, (test by pulling the plunger out as if you were turning on the lights) - rotate it and go thru a couple cycles, plug it into the harness and test it out (don't forget to reattach the battery cable if you had disconnected it earlier) - put the knee plate back on, and enjoy your properly working dimmer switch.
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Disclaimer: This post is here only to give you an idea of what it takes to go through this procedure. Your skills and results may vary.

 

[scoobyxj]

Good write up. This needs stickied.

 

[NW99XJ]

Thanks! I like doing this kind of stuff, and have been documenting the whole build-up process of my XJ over the last couple years, so I've kind of learned what helps people the most in doing write-ups - that and I like helping people out. So I hope this goes to good use for someone out there!

 

[5-90]

Nicely done!

I'd like to make a suggestion - over the years, I've found that a common rubber eraser works very well to clean copper card-edge contacts, and therefore also works well to clean switch pads like this. The regular pink eraser for pencil marks works well for general purpose, while the white/grey eraser means for ink marks works for when you need something a bit more aggressive.

I've gone so far as to keep a draughtsman's electric eraser in my electronic toolkit - it uses a "plug" of eraser about 1/4" in diameter and spins it, it's battery powered (and therefore cordless,) and works well when you need to maintain control in a tight area. You can get them at art houses or draughtsman's supply houses for a nominal fee, and pick up a packet of eraser plugs while you're there (it usually has a decent number of pink plugs and a couple of the white.)

 

[NW99XJ]

Thanks 5-90,
I coulda sworn I had mentioned the eraser trick as a suggestion for cleaning contacts, guess I thought it but didnt type it. I've used erasers to clean the oxidation off of contacts for years working in the mobile electronics field for over a decade. I typically use it for softer metal contacts like lead, gold, gold plating, etc... these appear to be more like an aluminum, and the eraser didn't do much, thats why I opted for something a little more aggressive. Great idea on the electric eraser idea! That'll save some elbow grease in the future.
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on another note, I'm super excited that this made to "sticky" status....
Thanks to all that chimed in and those who made the decision to bring this to the top of the list.

 

[5-90]

Thanks 5-90,
I coulda sworn I had mentioned the eraser trick as a suggestion for cleaning contacts, guess I thought it but didnt type it. I've used erasers to clean the oxidation off of contacts for years working in the mobile electronics field for over a decade. I typically use it for softer metal contacts like lead, gold, gold plating, etc... these appear to be more like an aluminum, and the eraser didn't do much, thats why I opted for something a little more aggressive. Great idea on the electric eraser idea! That'll save some elbow grease in the future.
>
on another note, I'm super excited that this made to "sticky" status....
Thanks to all that chimed in and those who made the decision to bring this to the top of the list.

I read it, thought it was good enough as it was, and saw that I wasn't the only one to think so. So, I stuck both this and your "LED Switch Bulb" replacement mod - they should be up.

Cleaning the earlier (1984-1996) headlamp switch is probably similar, but I won't swear to it. Likewise, I won't attest to whether replacing the bulbs in the switches will be the same - simply because it's been a while since I've seen the backside of one. But, something to chew on...

 

[scoobyxj]

Was easy as pie. I did mine today just because I had part of the dash apart.