Wiring help

[Renegade68]

Hi all, this is my new member post. I have recently acquired a 1968 D100 Custom LWB, 318, 3 on the tree, and 8 3/4 with 3.23s. Let me say it sure feels good owning a Sweptline! The truck sat for a little while and was robbed of some parts. The main thing being both battery cables. I was hoping that some one on here has some pictures or could take some of where the positive cable runs to and the where the ground cable is bolted to. Also I need to see what the wiring from the starter relay to the starter itself looks like as well. I am looking forward to learning a lot about these beautiful trucks and helping anyone I can. I am a mechanic at a local GM dealership but honestly I am a Dodge guy at heart. Any help, info, or photos would be greatly appreciated, Thank you!

[dodgeboykim]

Positive battery cable to stater relay on splash shield and another cable from relay lug to starter lug. smaller wire from small terminal on starter to terminal on starter relay. Wire to start circuit. Relay should be grounded to body. The 2 small wires on relay should be self explaining as to where they go. Ans one heavy wire (black i think) lead from battery terminal on starter relay goes to firewall and into dash. Hope that correct.

Battery ground to engine block. Make sure a heavy gauge wire from block to body at firewall (and one from battery post area to rad support if you want)

[Wildergarten]

Only things I'd add to what dodgeboykim said is to use star washers on electrical connections and at least a #4 AWG wire grounding the body from the firewall to the block. Getting a good bite from metal to metal helps break oxides that would otherwise impede the current. On my truck, I added a second ground from the battery lug to the frame. Unless you are running a winch or such, that could probably be #10 AWG. I might bond the truck bed to the frame as well. That connection is often a source of electrical troubles.

Welcome to the forum!

[dodgeboykim]

Only things I'd add to what dodgeboykim said is to use star washers on electrical connections and at least a #4 AWG wire grounding the body from the firewall to the block. Getting a good bite from metal to metal helps break oxides that would otherwise impede the current. On my truck, I added a second ground from the battery lug to the frame. Unless you are running a winch or such, that could probably be #10 AWG. I might bond the truck bed to the frame as well. That connection is often a source of electrical troubles.

Welcome to the forum!

You can never have too many grounds on an old vehicle.
And star washers are a good addition

[Wildergarten]

You can never have too many grounds on an old vehicle.

Actually, you can have too many in theory. With a high current device like a winch, if there is any resistance in the return path, one can induce a ground loop portential, which can cause havoc with some electronics.
https://en.wikipedia.org/wiki/Ground_lo ... tricity%29

[Renegade68]

Thanks for the info guys! The starter relay on mine is bolted to the driver inner fender I believe. Is that gonna be a problem?

[PwrWgnDrvr]

That's where the factory put them.

[dodgeboykim]

You can never have too many grounds on an old vehicle.

Actually, you can have too many in theory. With a high current device like a winch, if there is any resistance in the return path, one can induce a ground loop portential, which can cause havoc with some electronics.
https://en.wikipedia.org/wiki/Ground_lo ... tricity%29

Considering that most of the crowd here with Sweptlines don't really have extensive electronics that shouldn't really be an issue.
And an electric winch should have both Pos and Neg cables to battery.
When did Wikipedia become the final source for anything automotive related.

[Wildergarten]

Considering that most of the crowd here with Sweptlines don't really have extensive electronics that shouldn't really be an issue.

Maybe. I plan to use a short-wave set in mine in an area with pockets of poor reception (steep hills). So given that ground loops are easily avoided, it is best that people asking questions about grounding should be informed of them, don't you think?

And an electric winch should have both Pos and Neg cables to battery.

True indeed, possibly with a second battery and charged via an isolator and/or a marine battery switch, and... Interesting that this software doesn't have an emoji for dollar$.

When did Wikipedia become the final source for anything automotive related.

Nobody said that it was, or that definitive sources were desired or even possible.
Beyond simple functionality, "best" can get rather subjective as more considerations become involved.
Wikipedia is a handy search target and useful source of references. A good place to start.

[marklein]

Personally, I wouldn't use star washers on ground connections. They do no seal and will allow moisture to get to the connection. We see a massive amount of ground issues on newer vehicles and the biggest issue is surface prep and cable end prep. We see grounds put over undercoating, rusty metal, corroded cable ends. Clean is the most important thing. On my latest build, I am welding stainless bolts to my frame to use as ground points, the corrode less. Just clean your grounds well, use a flat washer, then cover with brush on electrical tape to seal them. Just my 02.

[PwrWgnDrvr]

They also make internal star washers - those would seal and still have the added "bite".

[sledgehammer]

Here are some pics from my ‘68. Little hard to see but this is where the ground from battery goes to engine block.

[sledgehammer]

More pics

[sledgehammer]

Closer view.

[sledgehammer]

I put a smaller starter on my slant 6.

[Renegade68]

Thank you so much for the pictures sledgehammer! I was confused about the starter relay but that makes perfect sense now.

[Wildergarten]

Thank you so much for the pictures sledgehammer! I was confused about the starter relay but that makes perfect sense now.

Looks like sledgehammer's truck has an automatic transmission. On a manual, the terminal on the upper left of the relay is grounded to the case. On an automatic it goes to the "neutral safety switch" on the transmission.

[64Powerwagon]

I grounded battery to block, block to frame, cab to frame and bed to frame. Sand to bare metal and use dielectric grease at all grounds and electrical connections.