The Stovebolt Site Forums The Shop Area The Electrical Bay why a jumper on a junction block?

Hello. I just noticed something weird under the hood on my truck. If you're standing in front of the truck and looking at the firewall, just to the left of the voltage regulator is a ceramic junction block. Coming off one side is a wire going to the starter motor, and coming off the other side is a wire going to the coil. I assume the "function of this junction" is to always provide power to the starter, but provide power to the coil only when the key is on (I could be wrong).

Here's the weird part. Somebody in the last 20 years has jumpered together both sides or terminals of the junction block. I haven't yet removed the jumper to see what happens.

Q1: If my assumption in the first paragraph is correct, why would you want power to the starter but not to the coil? Maybe for the obvious reason of wanting to turn over the engine but not start it, such as when doing a compression test? But you could remove the coil wire to the distributor for that. Just curious.

Q2: What would be accomplished (or harmed) by installing this jumper? I'm curious what this person (probably my now-deceased step-father), was trying to accomplish. Seems like I may have continuous power to the coil, which, I think, would burn up the points???

Thanks.

This block is probably a bypass/ballast resistor. You can't see the coils in that back. Anyway someone has bypassed the bypass. The reason lies in if you have a 12V or 6V battery, an internally resisted coil or not (ink stamped on case), a foot start or electric solenoid..........don't disconnect the jumper until we can figure out what you have.
Also you need to describe EXACTLY where the wire to starter goes. What terminal?
Also you need to describe what wires are coming into the ceramic block.

It could be just a junction block. A place to terminate wires. A pic or two would help.
A 1951, 216 should not have had a ballast resistor, so that is curious.

Hello there, Bartamos. I went and looked, and I slightly misrepresented the routing of these wires.

Coming out of the firewall are a small wire from the ignition switch to the right-hand side of the ceramic block, and a large wire from the back of the combo-gauge on the dash that displays Gasoline level, Battery charge, Oil pressure, and Temperature, to the lug on the starter that the positive battery cable connects to, with the little cardboard insulator (the switch that gets depressed when you stomp on the starter pedal). This thick wire is a red herring, because it has nothing to do with the junction block, now that I think about it. But the small and large wires coming out of the firewall get bundled together, so my brain misled me, and I misled you.

The left side of the ceramic block has a small wire that goes directly to the coil. So it seems the only wiring on this block is a wire in from the ignition switch and a wire out to the coil. And the latter-day jumper. I’d post a picture, but I think we’re not supposed to embed pics in posts, and I don't have a hosting site.

Hope this helps. And thanks for your help.

We have a NEW picture posting feature. If you click edit, look way down at left bottom for a blue hypertext "attachment manager". You will need to resize your pics to 300MB, or less, first. Then follow the manager prompts. No more hosting. Don't necessarily need a picture now, Just FYI for the future.

Please answer:
1. Do you have a 12V or 6V battery? 12V conversion done on this truck? or still a 6V system.
2. Is your coil internally resisted or externally resisted? Ink marked on case.
3. Does your starter switch/button on top of starter.... have a side terminal as well has a big lug? If it has a side terminal, is there a wire connected to it?
4. Do you have an ammeter hooked up?
5. Do you have non electric temp and oil pressure? (mechanical)
6. How many wires on positive terminal of coil?
7. I don't remember, does the motor run? Run good? Starts good?

I think I have a final answer figured out but want to be sure, after the above questions are answered.

Picture attached.

Ah, you tricked me and added more questions.

1. Battery is 6 volt.
2. The coil has a white dot (looks like manually painted-on white-out), beside the negative terminal.
3. Starter switch is on top of starter, no side terminal.
4. Ammeter? No, not to my knowledge.
5. Mechanical temp and oil pressure? I think so. E.g., oil pressure uses like a capillary tube or similar.
6. Number of wires on positive terminal of coil = 1.
7. Motor runs, starts fine. Recently adjusted idle and reconnected a vacuum hose that had been open to air for years, so she runs relatively very well. Timing's next!


Thanks.

Yes I was typing. I'm slow.

Someone has added a ballast resistor which is not necessary on a 6V system. Then they realized it and bypassed it. You can leave it jumped or connect the wires to the same post and leave the other post vacant or butt splice them together and remove the block. Why they did it is unknown. The ballast is for a 12V system. You are good to go.

P.S. Time to rewire and get rid of those old fraying wires!!

So, this thing that I've been referring to as a junction block (based on my interpretation of the Factory Assembly Manual), is really a ballast resistor? Interesting. I'll have to look that up. Thanks for your help!

Yes, my wiring is a hazard. Half the time when I'm working I touch the horn wire with a tool and she honks at me.

I think that big gauge wire from starter is supposed to go to ammeter and branch out, but check the schematic.
You need to address the wires ASAP. You can have some bad things happen if a short occurs. Not many, if any, fuses on that truck. Previous owners/relatives could do things that cause more unsafe conditions.