[BAB]

Specs/ 70 GTO / 10 DN 37 amp alt.-NAPA / Echlin-NAPA external voltager regulator.

OK...my generator light was staying on after the key was off so upon some testing I fired my external voltage regulator (dumb mistake) and replaced it with a NAPA premium mechanical regulator and still had my dash light on with the key on. I then went through the ign switch (which turned out OK) and then took my alternator apart to discover some bad diodes (1 with broken wire and another diode with no contintuity). I ordered a rebuild kit off the internet to rebuild my orginal alt at my own leisure and ordered a NAPA premium 37 am alt. to use in the meantime as well as for parts later (actually a pretty good piece). Since I replaced my alt. and regulator I resolved the light staying on after the key is off but now have my generator light come on intermittently below 1000 RPM and get a buzzing from the VR. I took the first NAPA VR back to for an exchange and have the same issue. When I check my DC voltage at battery, alternator, and terminal 3 they all match with 13.5 to 14.7 volts above 1000 RPM's however below 1000 RPM the light and buzzing returns and my DC voltage in the same check points goes to 16 volts! Why does my light and buzzing come back if the voltage is high vs. low and how do I troubleshoot?

Thanks for any help,

[BAB]

Update:

1. I removed both factory (copper) ground straps and cleaned the ends, mounting
points and bolts.
2. I cleaned the battery post
3. I removed the neg. battery cable and cleaned both ends and mounting point on
engine.
4. I removed the VR and dremel brushed the 3 mounting points to the firewall and
remounted.
5. Restarted the car and issue was gone with 14.2-14.5 volts at idle and during
revving.
6. I thought I had it licked so I shut the car off and returned for a drive. Issue is back and anything around 900 RPM's returns my light and buzzing along with 16+ volts at idle (at battery and #3 terminal).
7. Still looking for some sound advice.

Thanks,

[BAB]

OK...since the orginal e-mail I have tried 2 other voltage regulators from NAPA and swapped out another alternator with the same issue. At this point I think it is safe to rule out the alternator or VR. Now I am really at a loss? Any advice guys?

[Old Goat 67]

See your other post.

[BAB]

OK...I ran negative jumper wire from VR to neg battery post and the result was no change. I than did the same thing from the back of the alternator with no change. When I measured the voltage again at idle it was within range even though the light was still on and the VR was buzzing. I then revved it up to ensure the alt. set point had kicked in and when I did that the light and buzzing continues as normal but the voltage hovers around 16 volts.

[BAB]

Did some more voltage testing at idle and this is what my readings were. Anything above 900-1000RPM's and the light goes off and all readings are normal:

Battery: 16.65
Alternator Battery Post: 16.77
Alternator "R" terminal (black/white wire): 8.38
Alternator "F" terminal (blue) roughly 10.5 (jumps up down alot)

Regulator "4" Brown: 10.60-10.70
Regulator "3" (Black / Red) 16.76
Regulator "2" (Black / White) 8.38
Regulator "F" (Blue) roughly 10.5 (jumps up down alot)

[BAB]

Good news is problem has been discovered! Bad news is it took a "solid state" regulator from the Parts Place to resolve the issue since 2- NAPA mechanical regulators (echlin VR142) both did the same thing? I really don't like the fact I don't have orginal style parts or the troubleshooting 2 bad VR has caused but for now it's good. I'll go back to NAPA and trade out again (if they believe me) to find a mechanical regulator that actually works. Thanks for everyone's help since I received an eductation.

P.S. The solid state holds the voltage VERY consistent at all RPM's & idle (14.33 volts)