How does a 76 C10 get its main power feed

[pound41]

Hello
My Dad's old truck 1976 c10 stepside 454. When I turn the key I get nothing.
The headlights don't come on with a good battery. I have several 71/72 Chevy blazers. They have a power lead coming off the positive cable that mounts to the junction box on the fender. From there it feeds the power to the truck. That would be where I would start if I had an issue like this with that truck. I see a junction box on the firewall of my dads truck. But there is not feed coming directly from the positive cable. So how do I start to trouble shoot and chase the problem. Any help is greatly appreciated.

[ray_mcavoy]

You're on the right track with that junction box on the firewall. That should be receiving power via a wire that comes from the BATT stud on the starter solenoid.

[bhc41051]

Here's a link to forum member hatzie's shop manuals http://67-72chevytrucks.com/vboard/s...d.php?t=545416

[Dead Parrot]

Assuming it is wired per factory specs, the headlights should work without the key. Start with the simple things first. Batt ground should go to the alternator bracket and a ground strap from the passenger side back valve cover bolt to the cab(the strap is often missing). Possible the batt cables are rotted on the inside.

There should be a batt terminal in the cab fuse box that is hot all the time. Once you get power there, testing should go pretty fast.

[hatzie]

The ground strap should run from one of the drilled and tapped accessory bracket holes in the RH cylinder head to the cab.

Look at the 1976 wiring diagrams. THE FOLLOWING IS 1976 SPECIFIC.
In 1976 main power feeds (Circuit-2) is run through a fusible link on the BAT stud of the starter to the J-studs on the firewall next to the brake booster. Other years may have two or three fusible links 1976 has one.
The Circuit-2 output runs from there to;
the V & BAT terminals of the alternator.
the Bulkhead plug on the firewall into the cab.

Inside the 1976 cab you will find a splice that routes power to several points inside the cab. See the wiring diagrams for where.

If the fusible link at the starter fails on a 1976 truck all power to the interior of the cab is shut off. You can check for power at the J-Studs on the firewall. If there's no power there you have a break between the J-Studs and the Starter BAT stud... Probably the fusible link. On a 1976 V8 the fusible link is 14 gauge attaching to a RED 10 gauge SXL power feed wire per the wiring diagrams.

Circuit-2 power distribution varies a lot over the 1973-1991 model years. The above only applies to 1976. You should consult your model year wiring diagrams.