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Old 01-31-2014, 12:25 AM   #1
burningsquirrels
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Introduction and electrical questions on 67 c20

Hey guys, first post. Long time member as occasional troll since 2006. I am helping a buddy of mine work on his C20. It has a 327 with a 4 speed. Everything on the truck was original and in good running shape, except for one of the heads that had a couple bad valve seats. Non factory stuff included just an edelbrock carb and a newer exhaust system off the manifolds. It also had a newer alternator that had two blade prongs, a battery wire post, and a ground post (more on this in a bit)

We replaced the cylinder heads with a pair of camel hump heads I had sitting around for a while, and he gave it a ten foot paint job and a new tailgate. When we buttoned it up, I buttoned the starter up and put in a spin-on oil filter adapter and replaced the cooling system. He wired up the points distributor, coil, alternator, fuel system.

Well, long story short, we were cranking but had no spark. We were troubleshooting this when we realized that both of us realized another problem that the alternator wasn't hooked up. I asked him where the harness was for it, he dug around in the fender and whoops, it shorted on the fender. Disconnected the battery, replaced the wires (a foot worth), checked fuses (looked normal), it seemed alright. We weren't sure which went to what on the distributor at the time, so we lay the wires on the side and kept crankin'.

Eventually we found that the coil was bad, so we dropped in a coil in cap HEI and it fired up on the first try like we never had it apart. Runs and drives great with the new heads and distributor. Problem that remains now is the charging system.

We're not sure about the two plugs in the middle that go to the alternator, they are arranged like this: "--" in line, as opposed to side by side like this "||". I believe this is internally regulated. I didn't see the voltage regulator, I believe after looking around here it's behind the passenger side headlight on the core support? (Truck is not here with me today, will be tomorrow).

We did some tests to try and figure out what the plugs are supposed to do. This worked fine and charged the battery before, but we don't want to just jam the plugs on and hope it works. One plug has a purple wire (which I believe goes to the ignition switch and terminal 1) and the other has a white wire (which I believe goes to terminal 2).

Is there some way we can verify which goes to which before plugging them in? With the engine on, the only place we get voltage is the normal 12.6 volts off the big red hot post, instead of the usual 13-14+ volts I was expecting. Are the terminals (1 or 2) on the alternator supposed to put out some current to tell the alternator what to do? Is either purple or white wires supposed to put out current? Is purple on 1 and white on 2 correct? Is not having these two plugged up keeping the dash from powering up? I'm afraid that we may have shorted them when the four wires got jacked. Lastly, could there be a voltage regulator still hooked up that I didn't find? The fuses check out OK. The instrument panel does not light up.

Was hoping to try and sort this out by asking the few questions above? I head back tomorrow to take a second look in the afternoon and would appreciate a hand at getting a list of things to check.... Thanks!
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Old 01-31-2014, 12:37 AM   #2
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Re: Introduction and electrical questions on 67 c20

I was going to welcome you to the forum, but you've been a member longer than me!
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Old 01-31-2014, 01:23 AM   #3
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Re: Introduction and electrical questions on 67 c20

On my 67 C20, the voltage regulator is on the drivers side mounted to the core support next to the radiator. As far as your alternator, no frickin clue. According to the wiring diagram in my manual, there should be a 12Red, 16white, 16dark blue, 12black, and 18black going into the alternator. The only purple I see is the one (20gauge) that runs to the front turn signals and the one (12gauge) in the engine harness that goes to the starter.
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Old 01-31-2014, 01:32 AM   #4
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Re: Introduction and electrical questions on 67 c20

Here's the wiring diagram. Hope it helps.
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Old 01-31-2014, 02:17 AM   #5
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Re: Introduction and electrical questions on 67 c20

Like Willie, since I can't welcome you to the site, how about Welcome to your first post!

Anyway, I moved this to the Electrical section to help you get some specialized help. I'm sure someone with past experience with this problem or electrical know-how will be along to offer you some insight. Good luck!
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Old 01-31-2014, 01:58 PM   #6
burningsquirrels
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Re: Introduction and electrical questions on 67 c20

Thanks for the welcome and input, guys. I was looking to work on the truck today but it's delayed with some errands. I hope to put up some pics of the truck soon and the wiring stuff.

Thanks for the wiring diagram! That is going to help a bunch.
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Old 02-02-2014, 09:35 AM   #7
95gATL
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Re: Introduction and electrical questions on 67 c20

To add to the 1967's issues.....

The instrument cluster is not working (except for oil pressure). hence no fuel, temp, or amp gauges. They were working prior to all this. Could this be caused by the Voltage Regulator?
OR is there an instrument cluster voltage regulator behind the dash?

I plan on getting a new voltage regulator today and installing it ---hope that the battery will at least charge.
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