No Voltometer/Dome Light (Related?)

[KDMatt]

Very random, very 'all of a sudden' ...

I left the gas station after refueling and discovered that my voltometer was pinned all the way to the left, indicating a big fat zero for system voltage (which was obviously impossible, seeing as the car was running and the lights were on, etc.)

I confirmed the operational status of the electronics by taking my multimeter to the battery -- I got a nice steady 13.5 at idle (with lights on) and about 14.1 revved up (with lights still on), so I know the system is absolutely fine.

The weird thing is, the dome light also stopped working after the same stop that caused the voltometer to stop working, coincidence?

I don't have my FSM right in front of me (and even if it were, I'm terrible with schematics anyway), but I'm curious if there's any remote chance that the light and voltometer share a relay/fuse/ground/circuit somewhere.

Otherwise I'm open to possible suggestions for getting the voltometer to work again. I don't think anything is physically wrong with the guage, as I can bang on the top of the dash and it still bounces, it just seems to be behaving as though it isn't even hooked up.

Help is appreciated, thanks folks!

[TomoHawk]

On a 78

The dome light grounds through the door switch, but it also has its own ground connection. The voltmeter has a separate plug (a 3 pin pconnector) just for the volts part of the gauge, and its own ground connection. If the gauge indicates zero, then either the gauge has failed or the plug/connection/wire has broken the circuit. You should be able to measure the volts directly at that plug.

Edited August 26, 2009 by TomoHawk

[KDMatt]

Thanks Tomohawk. Perhaps I just happened to burn out the bulb or something by coincidence.

I've got my FSM right in front of me now, and as I'm peering through it, it looks like the voltometer and map light DO however share a connector/connection... because in addition to the dome light going out, I also no longer have the use of my map light.

Now that it's daylight I'm going to go do some poking around with my multimeter just to see what's what.

In the FSM I see a schematic (figure BE-73) that shows the fuel/volt gauge connected to a fuse coming off of the ignition relay ... thing is, the fuel gauge still works just fine, 'wonder if losing that fuse would cause me just to lose the voltometer or both fuel and volts would go...

[KDMatt]

OK, still digging.

Fuses all check out fine, as do fusible links.

Dome light won't turn on however the bulb is fine, reads continuity on the multimeter.

So now I'm very very confused, and the FSM isn't being of much help to enlighten me today.

Got the bezel on the dash removed, getting ready to poke around in there too.

EDIT:

FSM talks about an "Instrument Harness" -- that seems to be the one thing that all three of these components have in common, but where I go from here is absolutely beyond me. I can't identify this harness... and even if I could, I've got no idea what to test or how. I feel like I'm just shooting in the dark, and with it being the absolute peak of allergy season, my patience is a bit strained...

Help please. I'm totally lost.

EDIT EDIT:

Also noticed that the clock isn't working either now... on the bright side at least I know exactly when everything stopped working?

Edited August 26, 2009 by KDMatt