Instrument lights are out

[MrWampus]

Vexing problem here. I pulled the instrument panel out a bit (Not all the way because I didn't want to drop the steering column) so I could get to the clock that wasn't running. I removed the clock to see if there was anything obviously wrong, didn't see any loose wires. So I put the clock back in and reconnected it but now none of the gauge illumination works on any of the gauges (speedo, tach, fuel, temp, clock). Everything worked before I pulled and reinstalled the clock. (incidently, the clock now runs but I can't set the time because the adjustment knob seems a little out of kilter) What might I have jostled loose to kill all of the back-lighting for my gauges at the same time? I wanted to check all the easy stuff before I go to the next level of dropping the steering column and completely removing the instrument panel to get to the deeper set of connectors. (Also it isn't just that the dimmer is shut off, that's the first thing I checked. )

Thoughts?

[rlux4]

We'd need to know what year your car is to look up a wiring diagram, but meantime first thing I'd check is fuses. Could be a wire got shorted.
Ron

[MrWampus]

Duh, yes you sure do, sorry. It's an 81 Spider 5-speed. I just added that to my signature too so when I forget to add that bit of information again (which I will) I'll have a backup.

I found a great wiring diagram on Mirafiori that really helped. I did also check the fuses and they all seem to be intact. I wiggled them all too to make sure there was good contact.

The gauges themselves work fine, it's just the lighting. Even the green headlight-on indicator and the blue hi-beam indicators work but none of the backlighting.

The wiring diagram shows that all of the grounds from the lights go to a common connector and I have not tried yet to trace to that connector since it involves lying contorted on my back in the floor with a flashight trying to trace wires. Or, I drop the steering column, pull the instrument panel out, disconnect all the gauges and go at it from the front.

Before I do all that, I was hoping someone had had this issue before and could say, "Yep, it's simple. You turn your radio to 88.3, wack the left side of the steering column while pushing halfway in on the clutch and everything should be fine." (or something simple like that)

Also, I just noticed your signature, "26 years between spiders." I'm 25 years between them. I always regretted selling my first one.

[124JOE]

it might be a stupid question but

did you turn the dimmer knob down?

[rlux4]

I regretted selling mine too. In 1980 I had a 79 grigio fumo metallic beauty and got married. My wife had a Datsun 1600 Roadster, and she hated convertibles. So she convinced me that we needed a family car. 26 years later I was approaching 60 and she said that my riding a motorcycle scared her, and if I sold my Goldwing I could have another Spider. I put the Goldwing up for sale the next day.
Ron

[MrWampus]

Update: I found the problem! Turns out the dimmer module is bad. Why it picked the exact moment to fail when I was working on the clock is beyond me. I bought a cheap circuit tester at the autoparts store and found a good wiring diagram on line. Checked the input to the dimmer, had power, checked the output from the dimmer, no power. So for now I unplugged both leads and bridged them together with a short piece of wire and I now have nice bright instrument lights. I may leave it like that because I always had to keep the dimmer on full anyway. I'll add a new dimmer switch to the growing list of things to do.

Thanks for the advice, it led me to the source of the problem.

[rlux4]

I had the same problem a while back. I was able to repair the dimmer switch and it's as good as new. It's easy to open up, and when you do you'll see a rheostat, if yours did the same as mine, you'll find that the contact on the outgoing side of the rheostat has broken off. I just soldered a little piece of wire on it and it was good to go.
I knew i could buy a replacement, but I figured it wouldn't hurt to try fixing it first.
Ron

[Budduncan]

BTW, the dimmer is only a few ohms. About 8 ohms max as I recall. Either replace or play with the one you have. Has anyone purchased a heater fan motor lately? I bought one from VICKs last year and finally installed it. The wiring was correct, but there is only one speed on either leg with this one. It has off and high. The console switch is just a center to left or right contacts, but the only way I could get the fan to change speed was to wire in some series resistance. Since I seldom drive the car during winter or fall, I left the resistor out and just have High and Off. High comes on with the switch in either the left or right setting. Did the original motors have the resistance internally installed in them? Mine was a total meltdown of metal and platic, so I could not investigate. I love the design of the fan always being available, so if you bump the switch leaving the car overnight, you will have a dead battery in the morning, but we only do that once don't we!
Thanks
Bud

[JFreeman]

The rheostat is made with very small gauge wire that can burn out if shorted. I recall doing that once when working in the dash. Very puzzling problem that can only be fixed with a dimmer.

[MrWampus]

Thanks James, maybe that explains why it went out when I was trying to pull the clock. I must have shorted over to the power for the light with the metal bracket that holds the clock in. That would connect the light failure with the attempt to fix the clock. The clock is also the first light downstream from the dimmer. I guess that's yet another reason to disconnect the battery when fiddling with the electrics.

BTW Franklin, NC huh? My in-laws have a summer home in Highlands. Beautiful area and must be a great place to drive a spider.

[JFreeman]

BTW Franklin, NC huh? My in-laws have a summer home in Highlands. Beautiful area and must be a great place to drive a spider.

Yep, we moved up here about 5 years ago from Athens GA. We had a small weekend cabin for few years, but we sold that and built a bigger house at the time of the move. The family loves being here full time. The transition years were sort of bad for my Fiat hobby. It seemed we always had projects around the new house that took all of my time. I'm slowly but steadily getting back into it now. And you're right, the roads around here scream to be driven on!

James