totally stumped electrically...HELP

[BobB66SS]

I'm only getting about 11V on the Autometer gauge in my Chevelle and can't find the #$%&! cause.

Last weekend it seemed to be fine, reading about 14V at cruising speed and around 12 at idle, then I noticed it was only reading about 11 just before I got back home. Since then it showed 14V briefly when running in the garage, then dipped to 11 and hasn't budged since. Changes in engine speed have no effect on gauge reading, as if it's only reading static battery voltage. Battery reads 12V at key off. I figured I had a ground issue.

I have a one-wire alternator run by a March serpentine set-up. Since the alternator, bracket, and heads are all aluminum I've run a separate ground from the alternator to the chassis. Checked that for continuity and it's good. The block is cast iron and the motor mounts are all steel, no rubber. Have even run an add'l ground from motor to chassis, didn't help. Am getting voltage from the battery thru the alternator lead, as evidenced by the arcing when I mistakenly touched the lead against the head. Swapped the alternator for a new one, no change in readout.

Can't seem to get the alternator to excite (or at least read that it is) no matter what RPM the motor runs at. With the motor running the gauge reads about 11V. Turn on the parking lights and it drops to 10.5, add headlights and it drops to 10 so the gauge appears to be working.

Any suggestions on what else to look for or steps to take at this point? My background is mechanical engrg so talk slowly...

Thanks in advance.

[PRRC]

Sounds to me that its just not charging.Take a volt meter reading at the battery when its running it should be 13.8 to 14.2 if your system is working correctly.
Tim.

[6'9"Witha69]

Also check voltage at the distribution block. What did you do to the wires for the old external regulator?

[BobB66SS]

I don't get this thing. 11.75V at both the battery and distribution block when running. It's not charging, but why now?

The car's had a one-wire alternator on it for about 3 yrs. The only thing I changed was the bracketry mounting it to the heads. It's always run right at 14 when driving, around 12 at idle until this bracket change.

I didn't do the intial install from external to internal regulated; in fact the external regulator is still attached to the firewall but the leads are truncated. But again it's run as expected with that same configuration until this serpentine addition.

Suggestions??? Could it be the battery? It's a now 4-yr old Optima red top I installed new. It'll charge up to 12 on a trickle charger.

[MuscleRodz]

You may have the internal regulator failing.

Mike

[BobB66SS]

On 2 different brand new alternators? What would cause that? The second one never showed anything near 14V when first running, so could it fail instantaneously?

[6'9"Witha69]

Where are you getting the 1 wires from? A local guy? What cores does he use? What are the ratings of these alts?

[MuscleRodz]

On 2 different brand new alternators? What would cause that? The second one never showed anything near 14V when first running, so could it fail instantaneously?If from Autozone, then I could see it bad out of the box. If more than 1 alt has done this. I would check the charge wire for corrosion and double check your conversion wiring

Mike

[BobB66SS]

The first one was a 90A from Billet Specialties, the second is a 105A Powermaster from Summit. At this point all I figure I can do is to run new wires from the dist. block to the alternator and see if that solves the issue. Any other suggestions??

[BobB66SS]

Before I run new wire from the dist. block to the alternator, and before I tear open the old harness (which is really tucked away to hide it) to trace the old wire, is that the correct routing (dist. block direct to alternator)? Any reason not to run a new lead? I also assume I can ditch the old unused external regulator and truncate the leads running to it, yes?

Sorry for what probably seem like simplistic questions, just not a big wiring fan and don't want to make an ASSumption that would screw me.

Thanks.

[PRRC]

Hey, Bob lets back up a little. what kind of bracket set up did it have on it when it was working? Maybe a steel set up? and maybe you changed to billet set up? It could be as simple as a ground issue. try running a 10 guage wire from the alt direct to battery ground and see if it charges.just as a quick check.
Tim

[BobB66SS]

You're correct on the old vs. new setup. I had assumed it was a ground issue but nothing I've tried in that regard has helped. I ran a separate ground from alternator to chassis, and also tried a new motor to chassis ground, neither of which made any difference.

I'll try one direct to the battery ground as you suggest. Barring that working, what else would you suggest based on the other things I've tried?

Thanks.

[infotom]

Hey Bob, did the alternator location change? not enough wrap on the pulley causing slipping ? or belt configuration causing alternator to spin in reverse?

[BobB66SS]

Nope, same position as before. Driver's side high mount, outboard of the head. Same rotation as before (never heard of reverse rotation alternator, just w/p, which this system does have). Here's what it looks like from the March site. Belt tension seems good, thought that might be it too but no sign of that.

[MuscleRodz]

Have you had the battery load checked to see if it has a dead cell? I have kinda the same issue with my daily driver truck.

Mike

[BobB66SS]

This thing keeps getting weirder, though I think I have a bead on it now.

Ran a lead from the alternator to the battery ground, no change. Had the battery checked, it's fine. So I took both the old and new alt's to a local parts chain, both tested no good. Just to be sure, they tested one of their own new ones off the shelf, also bad. So they deduced their machine was not working. Went to the next local chain, they couldn't figure out what part number to put into the tester for a one-wire (I think we can all relate to the capabilities of most counter folks at the major chains). So I finally took them to a local mom and pop parts store and they knew exactly what to do to test them. Turns out both really are bad (as apparently was the one at the first chain, good call Rodz), and they tested one of theirs to be sure. Soooo...one goes back to Summit for a swap, the other might get rebuilt just to have around. I'll also run a new feed directly from the battery to the alternator just in case. We'll see if that solves it. Stupid hobby...