On one of my JY runs with Bill, I got a semi decent headlight switch for my 94. It had some crap that needed to be cleaned up before installation took place, so lastnight I decided to not only clean it, but tear it apart. What I found was interesting. Based upon my inspection this seems to be another failure related to plastic parts. Yes plastic.
Sorry for the low light pics but my camera sux and its on the list of things to upgrade.
Here is the switch together
There is a spring release on the switch that allows it to come apart as such
Next, there are two tabs on either side that need to be pryed up in order to remove the cover
Once the cover is off, the mechanism is quite simple and easy to figure out.
This is the plastic peice that holds the metal part that glides over the potentiometer. The metal ring, as I call it, goes onto the plastic only one way and the shaft for the switch runs through the entire assembly
After removing the plastic part, I noticed a black ring around it which indicates burnt plastic. Here is where I believe the failure takes place
The metal ring slides over that plastic part and then is held in by the metal bracket on the switch. When the plastic is new, there is very little movement for the metal ring to move.
Over time when the plastic heats up and burns, it reduces the plastics ability to hold the metal ring against the potentiometer firmly, which results in sporadic dashboard dimming control and the failure of the headlight switch.
This is just a theory upon my inspection of the switch and its componants. The onlly testing that I have done was to measure the amount of play of the metal ring while the switch was assembled. There was some noticable play but I still believe it to be in better shape than my switch that is currently installed.