Where there's smoke... Options

[flipb]

Why, oh, why, can't anything be simple??

I've been planning to pull off my instument panel to fix my odometer and replace the bulbs for night-time IP lighting.

The bulbs came today from PP and I ran out, eager to do something relatively simple. Unscrewed the IP and tilted it out. I admit, I was intimidated by the number of wires and decided to see if I could replace the IP lights (at least on the Tach) with everything still hanging out of the dash. There's one bulb near the top of the tach that was easy to pull. I took the bulb out of the socket and replaced it with a new one.

Turned the ignition to On, tried the lights, and the new bulb didn't light. Figured I didn't have it seated correctly in the holder, fidgeted and tried again. No light. I put the old bulb back into the holder and tried the lights...

Low hissing sound and LOTS of smoke from behind the IP. I'm guessing that by pulling on the IP, I shorted some wire back there? Can't tell the exact source of the smoke.

I don't have a lot of experience with electrical. What's my next move?

[VaccaRabite]

Pull out everything that is in the way of you getting you head and hands in there. Find the burned wire and fix it. put it all back together.

Zach

[flipb]

Culprit was a green/white wire that goes into the Speedometer.

The last 8" or so of wire have burnt up crispy bubbled sheathing. There were two spots where it had melted against a brown/ground wire.

If I just wrap the wire in electrical tape, will someone someday reflect on me as a DAPO?

[flipb]

And for the several times I've probably forgotten to say it - Thanks Zach and everyone else who's been pitching in with "snappy answers to stupid questions" with Flip. (Anybody remember what that's from??)

You guys rock.

Great couple days (today and tomorrow) in the Mid-Atlantic to get in a few last topless drives. Drove to work (downtown DC) for the first time in my teener today, then took a buddy to the airport via a roundabout tour of the GW Parkway and Arlington.

[jmill]

You have to understand one thing. No matter what you do or how good or bad you do it, once you sell your car you will forever be known as the DAPO.

[flipb]

I like illustrating things.

Here's the culprit wire.
(IMG:http://lh4.ggpht.com/_adaRwINBOu4/St-DCse2jBI/AAAAAAAAAqQ/ERyh29SiUVo/s800/IMGP0083.JPG)

Another shot - the wire comes out of this bundle - the bad wire is to the lower-left. Is that electrical tape something that a DAPO did?
(IMG:http://lh5.ggpht.com/_adaRwINBOu4/St-DzNNtpzI/AAAAAAAAAqs/i6qULM5PI3I/s800/IMGP0091.JPG)

[KaptKaos]

Might be easier if you remove the steering wheel, no?

[Spoke]

First thing to do when noodling around behind the instrument panel or fuse panel is disconnect the NEG lead to the battery. Usually the action of moving wires is when an accident happens. Once the desired instruments are visible, then re-connect the battery NEG terminal and check operation.

I used to pull the instrument panel out but found it's a lot easier to first pull out the tach, then reach around and back of the speedo and disconnect the speedo cable and pull the speedo out.

[flipb]

Might be easier if you remove the steering wheel, no?

I'm sure it would be. But this started out as just replacing a couple IP bulbs. Wasn't planning on getting complicated.

(Now I know... plan for anything to get complicated!)

[agentblr]

I think the green and white wire is the high beam indicator lamp,better check the whole circuit...

[flipb]

I think the green and white wire is the high beam indicator lamp,better check the whole circuit...

Interesting.

There are two green & white wires. Both come out of the bundle in my second picture. The one that goes to the right goes to the tach, and I presume is for the high beam indicator - which does not work. This one is white with green bands every couple inches.

The one that comes out to the left goes to the Speedo. It's white with a lengthwise green stripe/spiral. That's the one that's fried. Does it command the parking lights indicator? My parking light indicator stays on whenever any lights are on (parking, low beams, high beams, doesn't matter).

Does this help point to potential root cause?

[VaccaRabite]

Interesting.

There are two green & white wires. Both come out of the bundle in my second picture. The one that goes to the right goes to the tach, and I presume is for the high beam indicator - which does not work. This one is white with green bands every couple inches.

Check the wire diagram on your haynes manual. It will tell you exactly what wire it is.

Then cut all out all the burned section, use a butt connector to put in the new length of wire, and heat shrink rap the butt connector and an inch or two of wire to either side. Then use some non-black electrical tape and a sharpie marker to make a flag near the terminal that states what the wire is for future reference.

This is the non-DAPO (and also the "I don't want a flaming car") way to fix the issue.

And, yeah. Check the circuit.

Zach

[Gint]

And for the several times I've probably forgotten to say it - Thanks Zach and everyone else who's been pitching in with "snappy answers to stupid questions" with Flip. (Anybody remember what that's from??)

Yes. And that's a little scary...

Sorry I can't help as I'm no wiring genius.

[ahdoman]

KaptKaos is right - take off the steering wheel and the job is a lot easier! If you do that you can remove the speedo cable and the whole instrument console can sit face down on your steering column (put something for padding between the column and gauges). Then you can see everything and you won't be randomly pulling on wires. Also take Spokes advice and disconnect the negotive battery terminal. If you are replacing the bulbs with LEDs then you will not get any light unless your dimmer on the interior lights is turned all the way up. LEDs don't dim without other electronics.

[SLITS]

It's white w/ green trace. On a '74 it goes from headlight switch (term 57) to Parking Light Indicator Light.

[bandjoey]

U Electrical Mechanics can chime in on this:
Was told the LEd in the Alternator light position will cause the alt not to charge.

[neil30076]

U Electrical Mechanics can chime in on this:
Was told the LEd in the Alternator light position will cause the alt not to charge.

Correct, an LED is a low current light emitting device, and will not allow the required current to flow for the exciter circuit of the alternator, the alternator light must be a regular old fashioned bulb, 2 Watt, IIRC.

[rick 918-S]

U Electrical Mechanics can chime in on this:
Was told the LEd in the Alternator light position will cause the alt not to charge.

Correct, an LED is a low current light emitting device, and will not allow the required current to flow for the exciter circuit of the alternator, the alternator light must be a regular old fashioned bulb, 2 Watt, IIRC.

(IMG:style_emoticons/default/agree.gif) Ask Eric Shay what that cost him? (IMG:style_emoticons/default/unsure.gif)

[SLITS]

U Electrical Mechanics can chime in on this:
Was told the LEd in the Alternator light position will cause the alt not to charge.

Correct, an LED is a low current light emitting device, and will not allow the required current to flow for the exciter circuit of the alternator, the alternator light must be a regular old fashioned bulb, 2 Watt, IIRC.

(IMG:style_emoticons/default/agree.gif) Ask Eric Shay what that cost him? (IMG:style_emoticons/default/unsure.gif)

Heh heh heh .... go for it Salmon Boy. (IMG:style_emoticons/default/poke.gif) Rice is flavorless.

[flipb]

FWIW, I'm not using LEDs. Just replacing the IP lights with incandescent bulbs that are not older than I am, like the ones in there before.