Terminal block electrical short...

[1955cj5]

I remembered having read this some time ago. Thanks Tom Endy!

https://www.santaanitaas.org/wp-con...Hidden-Electrical-Fault-Terminal-Block-TE.pdf

Once I realized that this was the problem, repair i.e. insulating the studs was easy. Getting the box fastened back on the firewall, not so easy, but with help, we managed....

I had added a 30 amp fuse to the feed line some time ago. Glad I did.

The fuse would randomly blow....replace the fuse and all good for a while, then the fuse would blow again...

This time I noticed that the fuse would blow at the moment I pressed on the starter push rod and the starter engaged...the ammeter would momentarily peg to the left, and of course the fuse would blow.

Everything would work, headlights, taillights and horn, before engaging the starter, so somehow this must be related to the starter. Maybe not....

After much testing with a multi-meter and disconnecting things one at a time trying to isolate the problem, I had just about given up for the night, and began to replace the terminal box cover. It was just dark enough that when I put a little pressure on the terminal box stud, I could see the fuse blow...

So this is where Tom Endy's article surfaced...

I took the box off and sure enough the screws were exposed on the back side, and one was just the tiniest bit loose.....and there was a mark on the firewall where it had been making contact.

I insulated the heads of the screws with liquid electrical tape...green was all I had....then added electrical tape both to the box and the firewall.

Problem solved....

I could not find the "Hong Kong" marking on the box, but there were a few letters molded in next to the stud. FPRC. That box has been on there since at least 1962. It has a "Ford" script on the cover.

And the 10 amp fuse is in there just for troubleshooting...I normally run a 30 amp, but had blown them all by now!

 

[Gene F]

Re: Terminal box electrical short...

Those head on those studs looks awfully close. I wonder if a plastic washer on each of the four mounting screws, between the box and firewall might be appropriate?

 

[1955cj5]

Re: Terminal box electrical short...

I forgot to get a picture of the heads of the studs(slotted screws) before I insulated them, but there is an adequate gap as long as the screws are tight.

A little more clearance sure wouldn't hurt though.

I'd probably glue or somehow attach the washers to the box, as fiddling with the screws while holding the box from opposite sides of the firewall was was quite enough frustration....

 

[rotorwrench]

Re: Terminal box electrical short...

It could be in the ignition circuit or the charging circuit. A person should start looking for problems after the first fuse blows. The starter can't be fused due to the large amount of amperage it draws. The accessory fuse protects every thing else so it has to be narrowed down one step at a time to find the short.

 

[1955cj5]

Re: Terminal box electrical short...

It could be in the ignition circuit or the charging circuit. A person should start looking for problems after the first fuse blows. The starter can't be fused due to the large amount of amperage it draws. The accessory fuse protects every thing else so it has to be narrowed down one step at a time to find the short.

With the ignition key off the fuse still blew.....I even disconnected the red wire between the coil to my aftermarket ignition switch.

It had to be downstream of the ammeter to register on the ammeter when the short occurred.

I had disconnected the headlight harness and the generator.

And so it had to be between the ammeter and the terminal box, or in the terminal box.

I was beginning to think it was behind the instrument panel, maybe in the dash light wiring or socket.

I was fixated on the fuse blowing when the starter energized. For the life of me I could not figure out how those two events were related....I even took the starter switch off and took it apart...it looked normal.

 

[rotorwrench]

I had an instrument panel light wire short out on my 29. It didn't have a fuse back then so it burned up the little short pig tail from the light and the ammeter.

 

[Kurt in NJ]

Use a piece of gasket paper or piece of plastic from jug