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Old 02-09-2018, 03:28 AM   #7
hatzie
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Join Date: Oct 2008
Location: Wentworth, NH
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Re: update on 1979 K10. Everything dead but the lights

You're getting closer. It takes patience to troubleshoot wiring. If you don't have patience wiring will teach it to you. If you're getting extremely frustrated step back for a few minutes or hours to compose yourself. If it was easy everyone would do it.

The battery is just fine. It reads 12.43v cold and you've load tested it.

You have a solid ground and power connection to the starter now through the 2ga battery cables. You didn't before you fixed your ground. When you fix the rest of the problem it'll crank easier and charge well.

The starter should crank when you bypass the truck wiring with a remote starter switch across the BAT and S terminals on the solenoid.

If the cab power is completely dropping out when you turn the key to CRANK and staying off when you release it back to the ON position it's usually the battery cables or the three major distribution points...

You've verified the 2ga cable connections.

The last two major distribution points are the firewall J-Stud pair and the ignition switch.

Your ignition switch is new... I wouldn't completely rule it out but I'd check elsewhere first. I would take a gander at the plugs on the Ignition switch and make sure they're firmly seated in the sockets on the switch. Easy to check but probably not the issue.

In 1979 the J-Stud should have a fusible link feeding the ignition switch feed wire through the firewall bulkhead plug. This feeder wire is marked Circuit 2E in the wiring diagrams. If the wiring is original the alternator BAT wire is attached to the J-studs through the same fusible link as the RED Circuit 2E wire. Both studs should measure out to within .03v of full battery voltage all the time... the feeder wire that runs down to the starter BAT stud isn't switched.

NOTE: If the power weren't dropping completely out when you turn the key to CRANK and staying off when you release it back to ON I'd check the connections to and from the Neutral Safety switch or the clutch interlock switch and or the adjustment of whichever switch you have...
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1976 Chevy K20, 6.5L, NV4500/NP208 SOLD
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2000 GMC C2500, TD6.5L, NV4500
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RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials...Please include at least the year and model in your threads. It'll be easier to answer your questions.
And please let us know if and how your repairs were successful.

Last edited by hatzie; 02-09-2018 at 03:35 AM.
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