The joys of wiring....1965 c10 harness blues

[lha1992]

Hi all, well been working on my 65 c10. Yanked the original 283 an powerglide outta it with the help of member dillon rock on here. The truck is a original 283 powerglide custom cab BBW with all the gauge instruments in the cluster.

So I was doing some wiring an was planing on rebuilding my engine harness with new wires going to the starter an coil an because I'm getting rid of points. Well heres the thing the truck never would start on its own from the key so you'd have to jump it from the positive side on the battery to the s-terminal on the starter with speaker wire. I figure maybe the harness or the neutral safety switch which I have another mystery about that coming up too.

Anyways theirs 4 wires coming outta the big plug on the end. Purple is to the s-terminal, green to my thermostat gauge sender, that weird colored cloth wrapped one is the resistor wire I imagine which goes to the r-terminal on the starter which then in the background you see the yellow wire that comes to the coil from the starter BUT what is the black one???????

I'm dumbfounded as to what it is an kept looking at the wiring diagrams for awhile. Either I'm clueless an not realizing it but WHAT IS THE BLACK WIRE?

[lha1992]

Another mystery I have right now is the truck has a weird wire coming off the neutral safety switch going to the wires where the horn relay is on the core support. I'll take pictures for that.

[Lugnutz65]

This is from the FSM with my added color. Maybe it is the dark blue and not black. I hope it helps.

[lha1992]

Originally Posted by Lugnutz65

This is from the FSM with my added color. Maybe it is the dark blue and not black. I hope it helps.

Thank you for the help! That's the thing though my truck is an original all gauges cluster truck not warning lights. So why would their be a oil sender wire there at all? The date codes on the truck all point to the time of when the truck was built an everything.

[Lugnutz65]

Let me dig out my FSM and have a look.

[lha1992]

Originally Posted by Lugnutz65

Let me dig out my FSM and have a look.

Thanks brother! I'm quite lost as to what it could be at all. Been looking an trying to figure it out an nothing.

[ray_mcavoy]

That black wire is part of the factory ammeter ("BATT" gauge) wiring. It should go to the large BAT stud on the starter solenoid.

If you look up the wiring diagrams in the FSM, they don't show the optional factory gauge wiring for the 10-30 series trucks. You have to refer to the diagrams for the larger medium/heavy duty trucks instead.

GM put 4 amp inline fuses in the ammeter wiring on the later year 67-72 trucks. I highly recommend adding them to the 64-66 ammeter wiring. They'll save the ammeter and it's wiring from burning up if a poor connection develops on one end of the shunt wire and forces too much current to go through the ammeter itself.

[Lugnutz65]

These pics are from the wiring section of the 1965 FSM supplement. I compared these diagrams to the 1963 FSM and they look the same. All of the V8 wiring diagrams have a black wire (B) going to the middle post on the starter solenoid. Yes, the same post that has the POS+ battery cable. That means the black wire is HOT at all times. The other page shows the black wire (B) terminates on the AMMETER.

I'm trying to help but need to give a disclaimer. I am not an electrical guy so please check this info out with someone else before you fry your instrument panel because I gave bad info.

Here are the pics. from the FSM. The bottom of the page doesn't say C10 but ALL the V8 diagrams show the same wiring for the BLACK (B) wire.

[Lugnutz65]

Rats, Ray beat me to the answer! But ooooooonly because I was taking, editing and uploading pictures!

[lha1992]

Thanks guys for all the help! I really had no clue that that was for the ammeter. I looked at the wiring diagrams for the 10-30 trucks an nothing but as you said it wasnt to be found in the light duty trucks manual.

So with this do I need a big end hook to loop onto the BAT terminal on the starter?

An per suggestions from ray I will do the inline 4amp fuses on the black wire.

[lha1992]

You guys are the best thanks!!!!! :-)

[Lugnutz65]

Originally Posted by lha1992

So with this do I need a big end hook to loop onto the BAT terminal on the starter?

An per suggestions from ray I will do the inline 4amp fuses on the black wire.

That's what I would do. Ring connector on the starter end of the wire and an inline fuse.

[ray_mcavoy]

Originally Posted by Lugnutz65

That's what I would do. Ring connector on the starter end of the wire and an inline fuse.

I agree.

In addition to placing a 4A inline fuse in this black wire, I'd also recommend adding a second 4A inline fuse to the other leg of the ammeter wiring. One fuse is enough to protect against an overload due to a bad shunt connection (as I mentioned earlier) but a fuse in both wires will give full protection in case either side gets shorted to ground.

The other leg of the ammeter wiring is the black wire with a white stripe. It connects to the junction block on the horn relay (with a bunch of red wires) as shown in the diagram Lugnutz65 posted above. Locate the fuse close to the horn relay end of that wire.

[lha1992]

Originally Posted by ray_mcavoy

I agree.

In addition to placing a 4A inline fuse in this black wire, I'd also recommend adding a second 4A inline fuse to the other leg of the ammeter wiring. One fuse is enough to protect against an overload due to a bad shunt connection (as I mentioned earlier) but a fuse in both wires will give full protection in case either side gets shorted to ground.

The other leg of the ammeter wiring is the black wire with a white stripe. It connects to the junction block on the horn relay (with a bunch of red wires) as shown in the diagram Lugnutz65 posted above. Locate the fuse close to the horn relay end of that wire.

So you are saying place one on the wire that's listed B/W that goes to the horn relay from the ammeter?

My truck has had pretty bad hack jobs of PO's working on the wiring such as they put a volt meter in wired from some boxthing on the fire wall thatsn tied into the BAT terminal on the alternator that also feeds one of the spot lights. I'll get more pictures up in just a bit of it all.

[TJ's Chevy]

Ah the joys of wiring! Least some people here know how to do this stuff! LOL! When it comes to wiring for me..

[ray_mcavoy]

Originally Posted by lha1992

So you are saying place one on the wire that's listed B/W that goes to the horn relay from the ammeter?

Yes, that's the wire. I forgot to mention that the diagrams use the abbreviation "B/W" for black with white stripe but it looks like you figured that out

Originally Posted by lha1992

My truck has had pretty bad hack jobs of PO's working on the wiring such as they put a volt meter in wired from some boxthing on the fire wall thatsn tied into the BAT terminal on the alternator that also feeds one of the spot lights. I'll get more pictures up in just a bit of it all.

The fact that they added a volt meter is probably a good indication that the factory ammeter quit working. It could be as simple as that black wire no longer being connected to the starter solenoid BAT stud. But while you're working on the wiring, it would be a good idea to take a close look at the rest of the ammeter wiring (including the wires under the dash) just to make sure it's all in good condition and still connected as shown on the diagrams Lugnutz65 posted.

[Dillon Rock]

Heck man I should've given ya the wiring harness diagrams from my stash. I also have a new wiring harness sitting under the bench in the garage for the cab. All complete as far as I know. All I did was snag a fuse block clip for my radio spot and that's all I did to it. I'll let ya have it for nothing. No need for it on my part.

[1963c-10]

Originally Posted by lha1992

Thank you for the help! That's the thing though my truck is an original all gauges cluster truck not warning lights. So why would their be a oil sender wire there at all? The date codes on the truck all point to the time of when the truck was built an everything.

The oil gauges were plumbed in, no wires....the warning lights had wires for the oil warning light.

[kieth]

Wiring you either love it or hate it, I enjoy it, One thing we found as we added the wiring harness from a 91 suburban to my 66 gmc as we rebuilt it, was that GM had not changed the color codes from 66 to 91, all the old color codes still went to the same thing and new devices had new wires with new color codes. Sure made wiring the gauge cluster a lot easier to adapt to the newer wiring harness......Kieth

[1963c-10]

Now that's good info Keith....never knew that. Thanks..

[lha1992]

Originally Posted by T.J. MCCAULEY

Ah the joys of wiring! Least some people here know how to do this stuff! LOL! When it comes to wiring for me..

Hahaha wiring its fun but can be a challenge an can make you pull your hair out haha. All I say study those wiring diagrams. I work on vintage stereo equipment anyways with restoring those old things so doing this I kinda am use to it but still your working on a bigger scale an you don't wanna mess up something then go boom lol.

Originally Posted by ray_mcavoy

Yes, that's the wire. I forgot to mention that the diagrams use the abbreviation "B/W" for black with white stripe but it looks like you figured that out



The fact that they added a volt meter is probably a good indication that the factory ammeter quit working. It could be as simple as that black wire no longer being connected to the starter solenoid BAT stud. But while you're working on the wiring, it would be a good idea to take a close look at the rest of the ammeter wiring (including the wires under the dash) just to make sure it's all in good condition and still connected as shown on the diagrams Lugnutz65 posted.

Thanks for all the help ray! I am going to go ahead an check the rest of the ammeter wiring to be safe before hooking the gauge backup an sending power through all the wiring. You have a point maybe that's why they added it but idk the truck was setup to pullna trailer cross country apparently cause whoever owned it in the past traveled a lot which I'll post why they mighta added that meter in a bit.

Originally Posted by Dillon Rock

Heck man I should've given ya the wiring harness diagrams from my stash. I also have a new wiring harness sitting under the bench in the garage for the cab. All complete as far as I know. All I did was snag a fuse block clip for my radio spot and that's all I did to it. I'll let ya have it for nothing. No need for it on my part.

Thanks man!!! Its cool about the wiring diagrams I can use them when you get back. But that harness will for sure come in handy I can tell ya that!!! I owe you big time man thanks!!!

Originally Posted by 1963c-10

The oil gauges were plumbed in, no wires....the warning lights had wires for the oil warning light.

Exactly that's what my truck is is the oil gauge was plumbed in an how could it have a oil warning light which then with the help of the guys who posted above helped me find out the black wire was for the ammeter.

Originally Posted by kieth

Wiring you either love it or hate it, I enjoy it, One thing we found as we added the wiring harness from a 91 suburban to my 66 gmc as we rebuilt it, was that GM had not changed the color codes from 66 to 91, all the old color codes still went to the same thing and new devices had new wires with new color codes. Sure made wiring the gauge cluster a lot easier to adapt to the newer wiring harness......Kieth

Thanks for the info kieth!!! I'll deff check out the 73-87 trucks if I need anything extra.

[lha1992]

Well guys here's my next question an its a odd one I don't understand what the heck the previous owners were thinking? Unless I'm overlooking something yet again but anyways in the picture below you'll see the mess underneath my dash but look closely at the neutral safety switch an you'll see a brown wire hooked up.


An here's the mess.


Now that brown wire goes all the way through the firewall to some hookup on the horn relay! As you'll see below the brown wire hooked to the horn relay. And I'm not talking about the brown wire hooked directly to the horn I'm talking about the brown wire hooked to the center connection on the relay itself.



Here's a better picture where you can see the brown wire i'm talking about. (Not the brown wire hooked to the horn but the one on the horn relay)


Sooooo you guys what do you think that wire is running at all???

[ray_mcavoy]

Originally Posted by lha1992

Well guys here's my next question an its a odd one I don't understand what the heck the previous owners were thinking? Unless I'm overlooking something yet again but anyways in the picture below you'll see the mess underneath my dash but look closely at the neutral safety switch an you'll see a brown wire hooked up.

Now that brown wire goes all the way through the firewall to some hookup on the horn relay! As you'll see below the brown wire hooked to the horn relay.

The auto trans neutral safety switch also contains a set of contacts for reverse lights. They were an option on these trucks (and became standard equipment in '66). The 2 screw terminals on the horn relay are a BATT+ power distribution point.

It looks like someone added reverse lights to your truck and used the brown wire connected to the distribution point on the horn relay as their power source.

The factory installed reverse light wiring used a dark green power feed wire connected to the fuse box. Did they at least put an inline fuse in that brown wire?

Originally Posted by lha1992

An here's the mess.

Yikes! That does look like a mess!

Originally Posted by Dillon Rock

... I also have a new wiring harness sitting under the bench in the garage for the cab. All complete as far as I know. All I did was snag a fuse block clip for my radio spot and that's all I did to it. I'll let ya have it for nothing.

Looks like you're all set with a good harness to replace that mess though