Mystery electrical short

R

rundmt123

Member
So my 29 pickup has been out of commission for a few years after my son threw a gear through the transmission housing. Finally getting it back together. Was hoping to start it today. I have an aftermarket fuse block on the starter. When I went to start it I blew a fuse and now have blown several more. Can’t figure out why. I’ve checked the wiring and everything seems fine. I haven’t put on the main wiring harness so just the terminal box to generator harness and the instrument panel harness. Hoping for suggestions on what I’ve missed that could be causing me to draw too much current and blow fuses?
 
Disconnect the wire from the generator and see if it stops blowing the fuse, maybe the cutout is stuck closed.
 
Tap the top of the generator cutout a couple times with a small hammer or large wrench. The cutout's points sometimes stick, creating a short (or open?) and draining the battery. Was there a spark at a battery terminal post when the second battery cable touched it? If so, that will tell you there is a short somewhere in whatever wiring is in place. Remove one of the battery cables and then just brush touch it to its post. 'Got a spark, ya' got a short. If tapping the cutout doesn't clear up the problem, start disconnecting one wire at a time until you find the offending party. A frayed wire or wire flag touching metal can cause a short and blow out fuses.
Marshall
 
By the way, some of those fuse blocks that mount to the starter switch were very poorly made years ago. The connections were not properly soldered, leading to ignition misfires during power demands and blown fuses for no reason. I have removed a half dozen of those clunkers from Model A's over the years, whose owners were experiencing the symptoms I just mentioned. By-pass the fuse block and see what happens. If the wires feel hot to the touch and/or the battery cables spark when touched to their terminal posts, there is still a problem somewhere in the wiring.
M.
 
Hello, on some of the repro terminal blocks ,the one that mounts to firewall , the long screws can back out and touch metal, ,best to make sure they are seated and apply some rtv over them.
 
Thanks for all the suggestions. So far I cannot find it. Eliminated the cutout as
The issue. Took off the terminal block and eliminated it. Pulled off the dash and no issue I can find there. Really puzzled. At the point of rebuilding the entire electrical system from scratch.
 
Contrary to often repeated "cutout points are stuck" type comments, this is a very rare problem. I have repaired and adjusted hundreds of model A cutouts and restored hundreds of model A generators. I've seen ONE cutout with stuck points, and that one had extremely worn and eroded points. People often cast blame on the lowly cutout and think beating on it will solve the problem. Original Ford cutouts were very high quality and often just need cleaning, dressing of the points and adjustment to go another 20 years. When something does go wrong. Its usually the tiny shunt winding wire that breaks or shorts out.

If you'd like to learn more about servicing cutouts, check out my video.

https://youtu.be/rnuukBeJ6Zs?is=x9pfJhJ_PqCKwkDQ

Steve
 

Attachments

  • 20260315_130128_copy_908x515.jpg
    20260315_130128_copy_908x515.jpg
    27.3 KB · Views: 8
Check the fuse block, if the fuse doesn't blow before engaging the starter, there's possibly something wrong right there.
 
You must log in or register to reply here.
Back
Top