Conversions & Swaps LSX Engines in Non-LSX Vehicles
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Electrical Issue.

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Old Sep 23, 2010 | 11:48 PM
  #1  
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Default Electrical Issue.

Hey guys.

I'm very new to the world of LSX engines and love mine.

I'm running a 427 (GM LSX block), Big Stuff 3, T-56 Magnum and a Rick's Hot Rod Tank in a '71 GMC truck - very, very fun.

But.

I'm fighting with an Electrical issue.

The head lights were flickering and my Kicker Amp was cutting out, while the head unit was staying on. Also, this only happen while moving.

So, I had the new Powermaster Alt tested and ending up having it rebuilt.

I put everything back together tonight and it was fine, until I shut it off and the battery was dead. Ugh. It fired right with jumper cables. Sadly, I forgot to check the voltage before I shut it off in my garage.

So:

A) Battery toast? - it is 7ish years old.

B) I'm tracing grounds right now to make sure everything is tight.

C) Or there is a pile of stuff unhooked from the factory wiring harness - could something be screwing with me?

Any and all thoughts welcome - I want to hit the 1320 asap.

Cheers and thank you,
Bovey
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Old Sep 24, 2010 | 12:02 PM
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I would try replacing the battery and then check voltage at the alternator with it running.
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Old Sep 24, 2010 | 10:07 PM
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Yup.

Battery is fresh.

As mentioned, the alt. was rebuilt and I saw it checked, but only Amps, now that I think of it.

Grounds are in place, tight and checked.

Yet, I'm only getting 12.2 V on the battery. Ugh.

I can see every wire and have checked each one a number of times.

So, this leads me to believe the alt. is at fault. Am I missing anything?

Cheers,
Mark
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Old Sep 25, 2010 | 10:56 AM
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check the voltage out of the alt witch the vehicle idling, if the alt is working right it should be around 14 with everything inside the car off. are you running heavy enough gage from the alternator for charging? I run 2 10ga wires from the alt post to the battery terminal on the starter for charging. 10 gage wire is only rated for 30amps so if you have a 100 amp alt you should really run at least 2 of them or run 2 8ga as 8 ga is rated at 40amps it just makes it easier on your electrical system
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Old Sep 25, 2010 | 03:39 PM
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Originally Posted by bovey
Hey guys.

I'm very new to the world of LSX engines and love mine.

I'm running a 427 (GM LSX block), Big Stuff 3, T-56 Magnum and a Rick's Hot Rod Tank in a '71 GMC truck - very, very fun.

But.

I'm fighting with an Electrical issue.

The head lights were flickering and my Kicker Amp was cutting out, while the head unit was staying on. Also, this only happen while moving.

So, I had the new Powermaster Alt tested and ending up having it rebuilt.

I put everything back together tonight and it was fine, until I shut it off and the battery was dead. Ugh. It fired right with jumper cables. Sadly, I forgot to check the voltage before I shut it off in my garage.

So:

A) Battery toast? - it is 7ish years old.

B) I'm tracing grounds right now to make sure everything is tight.

C) Or there is a pile of stuff unhooked from the factory wiring harness - could something be screwing with me?

Any and all thoughts welcome - I want to hit the 1320 asap.

Cheers and thank you,
Bovey
what did you do with all the wiring that would have gone to the factory external voltage regulator in the '71 truck? There is a bunch of wiring I removed when I converted over to an internally regulated alternator. I think there was something you had to connect too, to ensure battery power is fed correctly into the fuse block.
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Old Sep 25, 2010 | 10:20 PM
  #6  
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Sorry - failed to mention that detail. getting 12.2V at idle on the battery posts and when I check the lead at the Alt.

Also, should mention the system worked fine when it was first installed.

As for your question about the wire size I am only running one wire - will have to check the gauge, but it is large. However, I did check the resistance in all the wires with a meter at every point back to the frame and everything was perfect.

As for the old wiring harness and regulator - it was disconnected, but it still in the truck. I have created a closed system for charging, however something could be causing interference. I'm going to go through the disconnect stuff tomorrow and check if I'm getting 12V at the fuse panel - thanks for the tip.

More later.

Thank you.
Bovey
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Old Sep 25, 2010 | 10:34 PM
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On other thing.

The gauges.

They read correctly when the truck is out of gear or still, but read wrong when moving.

This system is stand alone too, except for power at the fuse panel.

I'll be spending more confused time in the garage tomorrow. I'm gonna solve this yet. Grr.

G-night.
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Old Sep 26, 2010 | 06:46 PM
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Small update.

4G wire from Alt to Battery.

Started removing unused old wiring harness.

No change.

Back at it tomorrow night.

Cheers.
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Old Sep 27, 2010 | 08:13 AM
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check grounds
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Old Sep 27, 2010 | 10:20 AM
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Originally Posted by oange ss
check grounds
X2, make sure you have a good ground from the Battery to the chassis from the Chassis to the motor. A bad ground will give you a lot of issues too.
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Old Sep 28, 2010 | 09:25 AM
  #11  
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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
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Old Sep 28, 2010 | 09:31 AM
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The alternator naturally excites after 3000rpm approximately and will charge the battery, but if you are idleing around it won't unless you have the L terminal wired to a resistance source. I didn't even think about that because in the cars with pcms the pcm has a pinout for the exciter so I assumed you had that still attached lol. Well there you have it haha problem solved
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