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View Full Version : Melted some wires in the 40


CardinalFJ60
12-06-2010, 04:59 PM
So...on "take two" when I finally put the cleaned up gauges back together, hooked things back up...this happened.:( :mad: I included a pic of the back of the cluster. I'm a at a loss. Seemed simple enough to remove and replace. guess not. (sigh)

subzali
12-06-2010, 05:07 PM
Ouch. Does a fusible link not protect the ammeter wire?

RicardoJM
12-06-2010, 05:22 PM
That is a bummer. Is that the wire going to the ammeter? On my FJ40 (1971) the wire to the ammeter runs from the starter to the gauge cluster. The big red cable from the battery goes to the starter.

Ouch. Does a fusible link not protect the ammeter wire?

On my 1971 it does not have a fusible link. One of my early learning experiences was a valve adjustment at Jeff Z.'s place. Upon finishing the adjustment, he was looking over my rig and noticed that the sheathing on my wire was melted away exposing the innards. He quickly set me up with a replacement and explained to me the severe nature of the situation. Subsequent to that, I managed to touch a wrench to the hot post on my alternator and burned through the insulation on that wire again:o. I fixed it and now am much better about following step #1 - disconnect the battery.

CardinalFJ60
12-06-2010, 07:59 PM
it seems to be the wire that runs straight from the battery to the ammeter?? it started to do smoke and melt seconds after putting the neg. back on the battery after buttoning everything up.

yeah - I dunno. seemed weird to me that it arced at the middle of the old pc board, (on attempt #1). I'll take pics of that, too. something weird is going on. I mean, I pulled it just to replace the bulbs and oil press. gauge.
:confused::confused:

Uncle Ben
12-06-2010, 10:57 PM
I would be checking the ammeter for a short circuit!

RicardoJM
12-07-2010, 08:38 AM
it seems to be the wire that runs straight from the battery to the ammeter?? it started to do smoke and melt seconds after putting the neg. back on the battery after buttoning everything up.

I have not seen the wire run straight from the battery. As I think about the routing on my truck, it is the same as if it ran straight from the battery. If it will help, I believe that I have spare ammeter for you, don't know the condition as I never installed it.

For the wire to get hot like that, there has to be a connection to ground. I would recommend checking for continuity between the posts of the ammeter and ground. If that is not it, then the start taking a close look at the wires coming off each post.

Uncle Ben
12-07-2010, 08:59 AM
I have not seen the wire run straight from the battery. As I think about the routing on my truck, it is the same as if it ran straight from the battery. If it will help, I believe that I have spare ammeter for you, don't know the condition as I never installed it.

For the wire to get hot like that, there has to be a connection to ground. I would recommend checking for continuity between the posts of the ammeter and ground. If that is not it, then the start taking a close look at the wires coming off each post.

The reason I suspect a shorted ammeter is the wire is burnt from terminal to terminal. When wires get shorted to ground they will burn from the point of the short to the power source. I would be shocked if there is a pinched wire. (no pun intended) It is always a good idea to run power wires from a separate terminal (like the starter lug or battery terminal on the alternator) unless they are Fusable link protected. Batteries produce very flammable fumes and not a good idea to have a potential fire source (shorted primary wire) running across the vents to a terminal.

Rzeppa
12-08-2010, 06:34 PM
There is a short to ground somewhere between the melted wire and the ammeter. When the ammeter arced originally it allowed a large amount of current to flow through the entire length of the run, and it would likely have melted some insulation along that run somewhere in addition to what we see on top of the battery.

In instances like this, a visual inspection will usually show right away where the insulation has melted and the bare conductor is touching a grounded surface.

As Kevin suggested, also take a DMM and check to make sure there is infinite resistance between each ammeter post and the backing plate it is mounted to.

FWIW, if the ammeter were shorted from post to post, nothing bad would happen except the meter wouldn't work. They are supposed to have very low resistance from post to post. Most of the current runs through a very low impedance shunt, and a little bit gets routed through the windings of the meter itself.

If it were me, I would replace the entire length of that run with new wire. Pretty heavy gauge - probably 12 or 10 would be good.

TIMZTOY
12-08-2010, 07:28 PM
Short to ground ! Ohm between the + side of the gauge and any know good ground with gauges hooked up. (dont hook up the melted wire) your readings should be either OL "out of limit" or in the "M" range "million" if its like 2ohm its bad ! Replace it.