Map Light Stays On

[Mick]

Ross is correct. That is a terminal for your dash lights.
The dome function works like this:
A ground signal comes into the switch on terminal"D". As you rotate your knob all the way counterclockwise you will feel a click. On the front of the switch, below the "D" terminal you can see a small lever. As the knob is rotated a part of the ceramic rheostat holder pushes that lever up. On the inside of the switch that lever closes a contact that sends the ground signal from "D" to the metal case of the headlight switch (which is grounded to your dash, when installed). When that happens (in theory, at least) the ground circuit is now complete for your dome light.
If you disconnect the wiring from your switch and you still have the problem you have eliminated the headlight switch as a possible cause.

Well, %#@$!. One part about getting old that really blows is forgetting you pulled that switch already for that very reason - and yes, the symptoms remained. I was taking another look on my last final, desperate step before totally re-uninstalling the instrument panel...

 

[Ross Wooldridge]

Clean the rheosrat, the D terminal stop at the end, the E1terminal and reciprocal female end and all that, and I bet things may go back to normal.

At least, when you do find the issue, it will be a simple thing that will make you slap your forehead!!

 

[Mick]

Clean the rheosrat, the D terminal stop at the end, the E1terminal and reciprocal female end and all that, and I bet things may go back to normal.

At least, when you do find the issue, it will be a simple thing that will make you slap your forehead!!

Maybe I should just buy another headlight switch. Worried about potential internal damage.

 

[Ross Wooldridge]

@Devinism said: "On the inside of the switch that lever closes a contact that sends the ground signal from "D" to the metal case of the headlight switch (which is grounded to your dash, when installed). When that happens (in theory, at least) the ground circuit is now complete for your dome light.

You need to ensure that this ground is in place. This and that toasty looking terminal are where I believe the issue may lie. No ground, the power will want to flow to the next available ground, which in this case may well be through the yellow grounded dome/door light wires, through the rheostat and D terminal stop.

The ground may be functioning when things are cool, but when it heats up, perhaps it pulls away from where it grounds somehow, and then the problem rears its ugly head.

 

[Mick]

@Devinism said: "On the inside of the switch that lever closes a contact that sends the ground signal from "D" to the metal case of the headlight switch (which is grounded to your dash, when installed). When that happens (in theory, at least) the ground circuit is now complete for your dome light.

You need to ensure that this ground is in place. This and that toasty looking terminal are where I believe the issue may lie. No ground, the power will want to flow to the next available ground, which in this case may well be through the yellow grounded dome/door light wires, through the rheostat and D terminal stop.

The ground may be functioning when things are cool, but when it heats up, perhaps it pulls away from where it grounds somehow, and then the problem rears its ugly head.

So, a ground switch inside the switch might be bad? Excuse my electrical ignorance.

 

[Mick]

Ok, I think I see what you're talking about.

 

[Ross Wooldridge]

The metal case of the switch is the ground he was referring to. If for some reason the switch is not grounding to the dash frame (or is intermittent), then that's the potential issue there.

 

[Mick]

That actually DOES make sense. When I replaced the switch 2-3 years ago, I rotated it onto it's side for easy access to the release button. Thus, the area grounded was minimal.

 

[mr. fix it]

Does this look like heat discoloration on the front terminal to anybody?

View attachment 389776

Mine was fried so bad that it melted the connector plug.

Looks like you found this one early.

 

[3175375]

The metal case of the switch is the ground he was referring to. If for some reason the switch is not grounding to the dash frame (or is intermittent), then that's the potential issue there.

Couldn’t a ground wire be added to the case of the switch and have that securely attach to a ground point?

 

[Ross Wooldridge]

I would think so. I expect the ground comes at the retaining nut to the dash though.

 

[Mick]

So that really can't factor in then. As noted earlier, I disconnected the headlight switch and still the interior lights came on.

 

[Mick]

Update:
1. Uninstalled dash.
2. Checked next section of wire - and at least visually - looks great.
3. Ammeter wires look great, as does the back of the meter.
4. Got to the headlight switch connector...
Taping job looked like one of mine. Unwrapped, and found wires twisted together, then taped.
I got to thinking about my last statement, @Ross Wooldridge, about having already taken this switch out of the equation once. Even disconnected from the headlight switch itself, does power still flow?
At any rate, going to repair headlight switch wiring and replace connector as well.

 

[Ross Wooldridge]

Ummm... yeah, that twist job is not kosher. Fix that properly with a good crimped butt connector and heat shrink at the very least. Also, those copper strands as twisted together look corroded themselves - they should be nice bright red copper, not brown. Get some good brass brushes and clean those strands up before you commit a connection to them.

Yes, power will still flow if it can find a pathway.

That connector looks BRUTAL. Evidence of both heat and corrosion on the E terminal previously discussed, and corrosion on the others. However, all is not lost, as the condition of the plastic matters little visually if it's doing its job - it's what lies within that is the trouble. All those connectors gotta come out and be wire brushed clean and or replaced and reinstalled.

 

[Mick]

Ummm... yeah, that twist job is not kosher. Fix that properly with a good crimped butt connector and heat shrink at the very least. Also, those copper strands as twisted together look corroded themselves - they should be nice bright red copper, not brown. Get some good brass brushes and clean those strands up before you commit a connection to them.

Yes, power will still flow if it can find a pathway.

That connector looks BRUTAL. Evidence of both heat and corrosion on the E terminal previously discussed, and corrosion on the others. However, all is not lost, as the condition of the plastic matters little visually if it's doing its job - it's what lies within that is the trouble. All those connectors gotta come out and be wire brushed clean and or replaced and reinstalled.

On it.

 

[live4theking]

You could also put a little De-Oxit on those connections for instance against further corrosion.

On a side note the nuts that are on ampmeter closest to the gauge, snug them up a little bit. That insulating washer shrinks over time and will allow the connection to not be tight. This standed me 206 miles from home. Thankfully I had AAA premium, I paid $24 for that ride on a tilt bed.

 

[Mick]

Update: Headlight switch connector wiring, once unwrapped, showed previous "repair". So, new butt connectors all around, heat shrink, tape.
Ammeter works again!
Door light problem persists!

 

[Ross Wooldridge]

Keep at it! Repairing that wiring is a good thing!

 

[Mick]

I wonder now if there isn't actual damage to the headlight switch itself. That or door plungers are next, I suppose.

 

[mr. fix it]

Take a minute to disconnect all the door light pin switches

it may help if the map light stays off