70 C20 no power!! HELP!!

[DEESTER157]

So I’ve got a 70 Model C20 that did not have an ignition or starter when I purchased it. Bought everything for the ignition and wired it up, bolted the starter on and wired it up, then hooked up a good battery and.....nothing! No headlights, dash lights, or any power at all inside the cab or anywhere. I have no idea why. On my starter I’ve got the hot wire that goes to my positive battery terminal hooked to my big post on the starter, yellow wire going to the R side(small post), and purple going to the S side(small post). Should there be anything else hooked to the big post besides my positive wire that goes straight to the battery? It’s like I have no power to my harness. What else could my problem be? If everything is hooked up right then is it possible that the positive wire is bad and I’m not getting juice down to the starter? I don’t see any other wires that could be hooked to the big post on my starter. Please let me know what y’all think. Thanks

[kwmech]

12v wire should come from the battery to the right fender electrical block. From there it winds around the core support to the firewall junction block after it ties in with the charge wire from the alt. Get a test light

[VetteVet]

here's a diagram of the stock wiring in the engine compartment showing the battery to starter to alternator connections. It also shows the wiring to the rest of the engine compartment components.






Here's the wiring to the alternator and regulator to show the charging system.



The small wire labeled "fusible link" carries all the battery power to the charging system and the cab power for the lights and key switch and the fuse panel. You must have that to get juice to the truck components and it protects them from shorts and possible fires and damage.

[DEESTER157]

Ok well that makes sense. I knew I had to be missing something. I’ll have to look at it this evening and see what I got. In the wire with the fusible link, what fuse should I put in there? Thanks

[DEESTER157]

Also on the harness that goes down to my starter, I have purple and yellow witch shows on the diagram but I also have a light green and dark green feeding down to my starter and I do not see this on the diagram. Any idea what these are for? Thanks

[LockDoc]

Originally Posted by DEESTER157

Ok well that makes sense. I knew I had to be missing something. I’ll have to look at it this evening and see what I got. In the wire with the fusible link, what fuse should I put in there? Thanks

There isn't a fuse in the fusible link. Here is an explanation of a fusible link....

"A fusible link acts much like a fuse, only it’s designed to handle a different type of potentially hazardous scenario. These links are actually strands of wire wrapped in a fireproof covering, and are thinner than the wiring harnesses they’re connected to. They are placed in-line between delicate harnesses and large sources of electrical current in your car—between the battery and alternator, for example. These links must transmit high-voltage electricity, but also protect the rest of the electrical system from dangerous spikes that could cause a fire. If there’s a surge, the link actually melts, as its resistance to heat is lower than that of the circuits it’s protecting. This cuts off power while protecting the engine bay from a conflagration, thanks to its fireproof wrapping."

You should be able to get one at an auto parts store. You will need to provide the parts guy the application you are using it on to make sure you get the correct one. Many times on these old trucks the fusible link will have been replaced with a regular wire. NOT a good idea.....

LockDoc

[DEESTER157]

Thanks for the diagrams and replies guys and thanks for the fuseable link def Lock! That makes perfect sense. Ill have to pick one up on my way home today. I think that solves that problem. Does anybody have any idea what the light green and dark green wires are that go down to my starter are? Thanks

[demian5]

Originally Posted by DEESTER157

Thanks for the diagrams and replies guys and thanks for the fuseable link def Lock! That makes perfect sense. Ill have to pick one up on my way home today. I think that solves that problem. Does anybody have any idea what the light green and dark green wires are that go down to my starter are? Thanks

One is the signal wire from the ignition switch to activate the starter, the other comes up to the coil to power the ignition I believe.

[A1971Blazer]

Originally Posted by DEESTER157

Thanks for the diagrams and replies guys and thanks for the fuseable link def Lock! That makes perfect sense. Ill have to pick one up on my way home today. I think that solves that problem. Does anybody have any idea what the light green and dark green wires are that go down to my starter are? Thanks

if they're the factory wires...the light green and dark green are for the backup lights....they shouldn't be attached to the starter...anywhere...

[DEESTER157]

Well the purple is the ignition switch and yellow is to the coil. In this same wire loom going down to my starter i have a light green and dark green. They come out exactly where my purple and yellow do for my starter so im confused about what they are. Any thoughts? I may have to take a picture.

[demian5]

Check the nut on the black junction box on the passenger fender and clean it first. Make sure you get power there.

[VetteVet]

Originally Posted by DEESTER157

Well the purple is the ignition switch and yellow is to the coil. In this same wire loom going down to my starter i have a light green and dark green. They come out exactly where my purple and yellow do for my starter so im confused about what they are. Any thoughts? I may have to take a picture.

As stated the light green and dark green wires are used for the backup light lights circuit, but they are shown in the diagram and do not go to the starter.

We have had discussions in a thread about using the starter solenoid to actuate a relay for the fuel pump(electrical), also to provide ignition power during starting when an oil pressure switch is used, to kill ignition power in the case of an accident or in case of low oil pressure. I have developed an idea for a theft deterrent using the R terminal on the starter which requires additional wiring, but in a stock configuration there are no other wires than the purple and yellow going to the starter solenoid.
It is incumbent on you to trace out these wires and see where they go. Possibly they are for an alarm system.

[DEESTER157]

Ok i see the green wires in the diagram going to the backup light switch so i know where those go now. Any idea where this switch is at under the hood so i can hook these up? Thanks

[VetteVet]

Originally Posted by DEESTER157

Ok i see the green wires in the diagram going to the backup light switch so i know where those go now. Any idea where this switch is at under the hood so i can hook these up? Thanks

The back up light wires originate at the fuse panel and they are reall just one wire.The dark green wire from the fuse panel goes to the NSS on the steering column(automatic trans) and to a switch on the standard trans and thence to the rear lights. After it leaves the switch it turns to light green.

[DEESTER157]

Ok, well they are kinda one wire (two wires but plastic coating is attached together side to side). Someone switched my truck over to a 700r4 so that would explain why these are not hooked to anything. Did these go to a switch that was actually on the manual trans or a switch under the hood. Im assuming they both go to this switch.

[VetteVet]

Originally Posted by DEESTER157

Ok, well they are kinda one wire (two wires but plastic coating is attached together side to side). Someone switched my truck over to a 700r4 so that would explain why these are not hooked to anything. Did these go to a switch that was actually on the manual trans or a switch under the hood. Im assuming they both go to this switch.

Referring to my previous post this is the neutral start switch. It is mounted on the steering column of trucks with automatic transmissions It shares the backup light wires with the purple starter solenoid wires and it connects the green backup light wires when the shift selector is put into reverse. You will need the plug that connects the two wires to the Neutral start switch.
The backup lights operate off this switch and are not dependent on which automatic transmission you have in the truck.

If you had a truck with a standard shift transmission the switch would be mounted on the transmission and the green wires would go there.

here is a picture of the column switch. I had a picture of the NSS with the wires attached but I haven't found it yet.





OK here you go.

[DEESTER157]

Ok thanks for the picks! I plan on going back to a manual trans so I’ll keep the wires like they are for now so I can hook them up to my manual trans when installed. I’ll just have to deal with no backup lights for now. I’ve still got the original column and all installed. Well now that I know that, does anyone know what gauge of fusible link wire I need to go from the battery to the electrical block on passenger fender? Thanks

[VetteVet]

Originally Posted by DEESTER157

Ok thanks for the picks! I plan on going back to a manual trans so I’ll keep the wires like they are for now so I can hook them up to my manual trans when installed. I’ll just have to deal with no backup lights for now. I’ve still got the original column and all installed. Well now that I know that, does anyone know what gauge of fusible link wire I need to go from the battery to the electrical block on passenger fender? Thanks

Just for your info: The starter wire terminal on the outside of the solenoid becomes hot when you engage the starter, so if you have the light green wire on there, and the rest of the backup light harness and bulbs are in good order, your backups should come on while you are cranking the engine.

Some of the standard shift models also had a column mounted switch but I don't remember which ones.

[A1971Blazer]

Not sure about these....but many manuals have the safety switch mounted to the clutch bracket....thereby preventing a start up unless the clutch pedal is depressed...

[DEESTER157]

Ok, I’ll have to look and see if i have a switch on the column. I’ve also still got the clutch pedal and stuff installed so I’ll have to look and see if it may be mounted there. Would this be inside the cab on the clutch bracket/pedal? Thanks