Interior light diagram and/or advice needed.

[Joe Bob]

My interior light decided to stop working in one function.....works fine with the door switches, open one or both...light goes on. The off switch works great...

The permanent on, does not. Doors open or closed, no joy. The under dash light above the glove box was the opposite....got it working last night when I cleaned the corrosion off the switch/plunger ground. Works in all functions.

I'm thinking maybe there is 'another' ground besides the switched ground in the doors? Or do I have the power switch on the wrong lead?

I was so happy to get the door switches working after replacing the fixture that I'm not sure if I ever had the permanent on function working....

[Joe Bob]

Dropped the fixture.....the lead on the left is 12v constant. The one on the right with the shield is ground and will go dormant when the door is shut, the one in the middle
w/o a shield is a constant ground.

Swapping the grounds moves the door switched activation to the other side of the rocker.

[Joe Bob]

The under dash fixture is not a toggle it has a black plastic 3 position switch. Pulling it out, the wiring is similar but double stranded indicating it powers something else down stream. Bentley wiring diagram indicates this is where the over head get 12v.

One ground, per Bentley, goes to the door switches and the other ground seems to be local and I have continuity on that other ground.

[donagain1]

JB, you may have ciphered this situation out by now, in which case I'm stating the obvious, but just in case... The pic shows a very clean and non-decayed fixture, and I'm assuming that you visually checked all the functionality of the contacts, etc. when toggled in both directions and found it to be in good order. Additionally you verified the presence of the constant 12V source battery (arrives there from Fuse #18, to the clock, then to the glove compartment light fixture, and on to a 4-lead junction splice which also feeds the key warning buzzer, luggage compartment light fixture, and of course yours). You've also confirmed functionality of the switched ground leads (br/wh with the insulated female spade-tip connector), when placed onto both sides of the rocker switch. The solid brown wire connects to one of the grounding points (or perhaps even the windshield frame itself) to provide a permanent ground for the non-doorswitch operated "On" function. Therein lies the stumper... you report that ALL the proper players are there at the switch, and moreover, by swapping the ground leads that both ground connections through the lampswitch operate properly... the #$(^%&$#-ing thing SHOULD WORK!!!

If you wanted to take things to an extreme, swap the switch with it's clone at the glovebox, and see if the trouble follows... which would make it obvious that the fixture is somehow fouled. Other than this, it's gotta be the brown wire's ground connection. Please post your resolution when you get it working.

[donagain1]

Oops you posted as I composed. Time for extreme measures. Strip a piece of wire on both ends and jumper between the lamp (the side away from the black wire) and the grounds, it lights the bulb in both positions, the fixture is bad.

[Joe Bob]

As I have mentioned....I have swapped both grounds on the right....all it did was reverse the working (door actuated) function on the rocker.

A test meter on the left (+) and test to ground on each lead on the right verifies 12v. The unshielded brown wire goes to ground just inside the hole for the fixture.

Except for swapping in another fixture I be flummoxed.....

[Joe Bob]

Gonna pull the whole fixture and bench test it.....

[donagain1]

Holy crap, it's time to call in Larry the Cable Guy or something, man. You've done everything right, it SHOULD WORK! Out of curiosity, are you testing it by toggling the switch while it's hanging down, or are you shoving it back into the hole to test it? If it's the latter, then maybe something is dislodging slightly when installed.

[Joe Bob]

Bench test....it's the fixture.

EDIT:....further probing with the ground spike, finds that 12v power comes in on position #1, nothing on #2, #3 SHOULD be getting power but it doesn't. The bridge is malfunctioning. I hate that when it happens.

As I mentioned, I don't think I ever checked if the permanent on ever worked and it came that way from the retailer. Not a huge deal but it low level pisses me off.

Oh well, put it back in and live with it and just open the door when I need interior light.

Based on my bench I have no idea why power reached position #3 when I swapped ground positions.....I hate electricity....

[donagain1]

Yup, continuity from the spadetip where the black wire connects should reach the lampholder spring in both side positions, and if yours isn't it's definitely the fixture alrighty. Oh well, what's another $46.75 to our host in the grand scheme of things, eh? It pays for what keeps us all here talking about this stuff.

[donagain1]

On the other hand, something seems rotten in Stuttgart... the wiring diagrams depict the toggling contact as selecting which ground is to be used, either the solid brown frame ground, or the doorswitched brown/white (with center position being neither). The 12V source should constantly be available at the lamp contact, not toggled depending upon which position the rocker is in.

[donagain1]

Ah-HA!!! Based upon your photo, the Black wire and the Brown/White wire are transposed. Swap them and it should work properly.

[Joe Bob]

Nope....that wasn't it....even re-installed it in the hole.

[donagain1]

Actually, yeah it is... although it may work either way. I pulled mine just to verify, and mine was as I described. That said, when I put mine back in the hole, it didn't work. During my manuevering to reconnect the spade tips, I twisted the contact. Because of that, it didn't touch the contact formed by the other end of the lamp spring. If you look REALLY closely at it (with adequate light) you can see the contact point when the switch rocks. My fix was to take a pair of thin longnose pliers, grasp the spadetip connector, and twist it ever so slightly in order to put the butt-end of it in the path of the lamp spring contact. After that it worked.

Here's the deal, unless the plastic is brittle or broken, and ***** is poking out all over the place, the gremlin is all in the alignment of the contacts. The

[Brian in VA]

JB mine didn't work pushed forward or back, but after just taking it all apart, lubing, stretching the spring a bit (that and the tiny ball bearing shot out and hit me in the face, I didn't see it at all before that and then searched under the couch for a long time so be carefull) it worked fine when all put back together. A little corosion and the contacts weren't touching the bearing if I recall.

[Joe Bob]

The unit, which I took over to a indy P-car wrench friend, looks brand new. Until the last couple of days I never moved the rocker from the door switch position. He couldn't figure it out either.....

Screw it, back in it goes and at the door rocker setting. Damn thing is 15 months old and sports a made in Germany sticker.....makes it go faster.

[Joe Bob]

Ordered the replacement part....out of stock but will be here August. I can live with it.