Fire under the dash...

[mmwb]

I’ve a 76 M880/W200. While plowing this morning, I had a small fire under the dash. A bit exciting for a minute, but got the lots done. There is a black 6 ga wire from the alternator to the firewall and a similar sized red one from the starter relay to the firewall. To the best I can determine, they meet at the ammeter, which I bypassed some time ago (ironically to avoid a fire). The black one shorted and burned through at the firewall under the dash. Am I right in assuming I can just splice, solder, and seal these under the hood?

[KRB64]

What caused the short? Did the firewall wear through the insulation and short it out there?

If so, then fixing that and adding a rubber grommet should be OK I'd think - but I'm no sparky. Was the alternator still charging? The fact that you were not dead in the water indicates that everything must be OK still.

At least you were proactive in trying to eliminate a potential problem by bypassing the ammeter. Lets see what those with better electrical knowledge have to say.

[712edf]

They can be spliced together elsewhere, just do note that other wires feed off of them under the dash in I'm not mistaken.

Bucky

[mmwb]

Thanks for the replies. Looking at the schematic, I don't see where other wires come off of them. It looks to me like the wire coming out of the firewall from the alternator had been broken down to a few strands. There is a lot of juice running through that circuit and I believe it may have just heated by resistance through the few remaining strands to where they melted.

The problem it caused was that I lost my charge to the batteries. After a temporary splice it was fine for a few hours of plowing last night.

I like having both an ammeter and voltmeter and may install a couple of high end ones, in which case I'll have to take them back through the firewall to the dash...

[n1265]

There is a black 6 ga wire from the alternator to the firewall and a similar sized red one from the starter relay to the firewall. To the best I can determine, they meet at the ammeter

This is correct and you can splice it together at the firewall, 712edf is also correct in saying that the black wire has others that splice off of it.
( or is suppose to if it has not been re wired ) It is called a
"welded factory splice " and is under the dash about 6" from the ammeter. It feeds the light switch, fuse panel, and a link to the ignition switch connector.


I ran a whole new wire from the alt to the splice, drilled a hole threw the firewall with a rubber gromet to get away from the old firewall connector.

[mmwb]

Thanks for the replies guys. I did run a piece of 6 gauge through a grommet and spliced everything back to together. I then put an after market ammeter and a voltmeter on. Its nice to know what is happening with the electrical system...

[n1265]

Good reading right here....


http://www.madelectrical.com/electri...-gauges2.shtml

[KRB64]

Definately. About as good and detailed instructions as you can get. I've had that earmarkked for a while but have yet to bypass any of mine.

[n1265]

Good reading right here....


http://www.madelectrical.com/electri...-gauges2.shtml

Here is the link for the Complete article, not just the fix ( second page as listed above ) also it should be noted that the factory wire is 10ga. instead of 6ga.



http://www.madelectrical.com/electri...p-gauges.shtml

[QuantumJo]

Nice article! I'll be doing this when the Adventurer comes apart. Thanks for the link.