Electrical Issue

[bovey]

Hey guys,

Short version. I'm looking for all the grounds on my '71 GMC.

Long version of this request is below.

Trying to figure out a charging/electrical issue. Originally traced it to the Alternator that had a faulty regular (Single wire conversion) and had it rebuilt. FYI - I witnessed the repaired Alt on a test stand and everything worked correctly.

Anyway, I hooked everything back up tonight and everything seemed fine until I shut the truck off and it would not start. It stated like a champ the moment I put jumper cables on it.

So, there is a chance the battery is toast as it is around 7ish years old.

But I want to check all the grounds. But where all all the grounds, it's been 20 years since I had this truck apart and I can't remember. Obviously, there is one on the engine, but is there any in the cab for the wiring harness?

Should mention that I'm running a Big Stuff 3 in combination with the original wiring harness and a single wire Powermaster Alt.

NOTE: When my shop rebuilt my brand new Powermaster Alternator (only had 7000 miles) - the could not believe how cheap some of the part where in it - given the regulator from Powermaster, they were amazed it ever charged at all.

Thanks in advance,
Bovey

[El Jay]

Here ya go.

http://67-72chevytrucks.com/vboard/s...=ground+straps

[cdowns]

each and every item that is driven by electrical needs a ground path not just 4 or 5 cables

[bovey]

Thanks for the link El Jay. When I searched I was always using grounds, never singular...

Back at it tonight.

[bovey]

Okay. Annoyed.

Grounds are solid.

Battery is fresh.

Alt. is rebuilt and checked. (Single wire conversion)

YET, the system is not charging. I'm only getting 12.2 volts on the battery. Yes, I have reved the engine over 2 grand to make sure it turns on.

So, this leads me to believe the alt is not charging again.

Am I missing something?

Cheers,
Bovey

[mr48chev]

Well you answered my questions one and two correctly. What is it charging at the stud on the alternator? Hooking the ground lead on the alternator frame or close to the alternator and the + lead to the stud would eliminate all of the wiring from the equation and tell you what you are getting at the alternator. It's hard to think that you might have a 1.5 or so voltage drop and a bit improbable but stranger things have happened. You may also have a bad lead or connection in the wiring between the alternator and the battery. Anything else you worked on that might affect the circuit while you were having the alternator worked on? All the right wires hooked to the junction stud on the inner fender by the battery?

[bovey]

The system is very simple. I use the main lead of the alt and run it directly to the battery.

The negative battery terminal runs straight to the head and the ground strap from the engine block to the frame is only 5" away.

I have check resistance in all the wires and it checks out along with a ground check.

Not running the battery reads about 12.5-12.6V. At Idle the battery reads 12.2 and the +terminal on the alt also reads 12.2.

Can't think of anything else I've changed. And the charging wiring route is all visible and basically it's own closed system with exception what runs off the battery and the + terminal on the fender.

Again, thanks for the tips. I'm gonna take another stab at it tomorrow for a bit and try to trace this out.

[bovey]

Hold on. Just thought of one other odd thing.

The guages.

They read fine with the truck is out of gear, but screw up once I start moving.

Here's the odd thing. There in not one wire attached to the tranny.

Very odd.

G-night.

[68 Stepside]

I had a somewhat similar problem a number of years ago. If I moved my shifter around, the gauges would go crazy, the radio would shut off briefly and the headlights would flicker. I fixed it with a good heavy ground wire from the cab to the frame.

[bovey]

Problem Solved.

But it does have a strange twist.

Turns out I was missing a small harness that tells the internal regulator to turn on. I've attached a photo of it - I'll make it sexy later.

Wire 1) The wire with the peanut bulb goes to the "L" terminal of the Alt. and must attached to an ignition source. This peanut light will be changed over to my idiot light soon.

Wire 2) This wire attaches to the large alt post the goes to the battery and runs to the "S" terminal.

When you turn the ignition on - the light will be on (wire 1) - and the internal alt regulator is on. When you start the engine the charge from the alt post going to the battery (wire 2) will turn off the light. This tells you the system is charging.

So, if that light ever turns on while the engine is running - the system is either over charging or under charging - hence an idiot light.

And here's the strange twist. I've never had this hooked up this way and I drove this truck on a non-stop 7000 mile -22 day Canada/USA road trip in July. How on earth was the system charging? I doubt the battery carried us all the way.

Puzzled, but it works now.

Thanks everyone for their suggestions and help.
Bovey

[VetteVet]

The idiot light is a 10 ohm light and might not be enough. I would go here and wire it like they did and you can still use the light. The brown wire from the firewall plug is the idiot light wire that used to go to the external voltage regulator so you can use it to wire the resistor into and run it to the L terminal. The S terminal wire is the sensing wire for the alternator and you will have better results if you wire it to the old regulator red wire or to the red wire splice in the harness. It is called remote sensing and will compensate for voltage drop in the other circuits.

You should hang out in the electrical forum. We have this issue at least once a week.

http://temp.corvetteforum.net/c3/zma...ternator01.htm

[69sixpackbee]

You need to get rid of that single wire unit!
Read this:
http://www.madelectrical.com/electri...evymain1.shtml

Long ago I s**t-canned my 'ol 10SI and went with a 12SI, 94Amp unit. I upgraded ALL of my wiring so that I could step up to a CS130 if need be.
Glad I did!

Bud