Stator terminal voltage without the alternator running?

[burntorange84]

Forgive me if this is obvious.

My battery is being drained on my '84. I pulled the charger off the battery, and felt the electric choke assembly; it's warm and the car hasn't run in over a week. Hmmm, check it and it has 6+ volts; check the alternator and it's outputting 7 volts at the S terminal, with the engine off and no key in the ignition.

I changed the voltage regulator a few months back, but the choke has been working properly until the last couple of times i drove it. It would drop down from high idle pretty quickly, but it has been over 105 degrees for weeks....until i found this problem.

What can cause this? I haven't started her up to see if she's charging yet.

-j

[KevinK]

I believe the purpose of the white star wire is to provide power while the alternator is spinning.i would unplug the voltage regulator and see if the power turns off.

[burntorange84]

It is to provide~6-7 volts to the electric choke, only when running.

I had pulled the wire to the choke this morning. I unplugged the voltage regulator this evening and the output on the choke wire is now 12 volts (battery voltage), and not running , and it was 6-7 this morning? The battery may be going out, it was 12.8 this morning. Plugged the voltage regulator back in and grounded the case, still now 12 volts?

-j

[BMW Rider]

You should only have power at the stator terminal when the alternator is spinning and producing current. The stator terminal is connected to the junction of the three winding sets in the alternator, the other ends of the windings connect to the diode pairs to convert the alternating current produced to a direct current. The only way you could have power at the stator terminal without the alternator spinning would be due to one or more shorted diodes allowing a backflow of current through the alternator. Probably it's just one diode which is the problem, this will also reduce the output of the alternator, but it would still likely produce enough current to appear to be still working, at least under light demand.

Short version, you need a new alternator.

[burntorange84]

Thanks for the tips guys.

I wouldn’t mind upgrading to 3G, but I think I’ll pull the alternator and replace the diode rectifier. Time is my problem, but I’ll look for the upgrade next time I go to the pick and pull yard. When I upgrade to an electric fuel pump, I’ll do the swap.

-j

[massacre]

You should only have power at the stator terminal when the alternator is spinning and producing current. The stator terminal is connected to the junction of the three winding sets in the alternator, the other ends of the windings connect to the diode pairs to convert the alternating current produced to a direct current. The only way you could have power at the stator terminal without the alternator spinning would be due to one or more shorted diodes allowing a backflow of current through the alternator. Probably it's just one diode which is the problem, this will also reduce the output of the alternator, but it would still likely produce enough current to appear to be still working, at least under light demand.

Short version, you need a new alternator.

Great post thanks

[KevinK]

You should only have power at the stator terminal when the alternator is spinning and producing current. The stator terminal is connected to the junction of the three winding sets in the alternator, the other ends of the windings connect to the diode pairs to convert the alternating current produced to a direct current. The only way you could have power at the stator terminal without the alternator spinning would be due to one or more shorted diodes allowing a backflow of current through the alternator. Probably it's just one diode which is the problem, this will also reduce the output of the alternator, but it would still likely produce enough current to appear to be still working, at least under light demand..
Short version, you need a new alternator.

Kind of where I was leading to. Ruling out the voltage regulator. Only leaves 1 thing left. Thanks for the technical explanation. They are repairable

[liv2roc]

what carb you running? I'm running a edelbrock and it says do not connect the chock to the alternator, connect to a keyed 12 volt source.

[gr79]

what carb you running? I'm running a edelbrock and it says do not connect the chock to the alternator, connect to a keyed 12 volt source.

Spliced a small 5a fuse and holder to the alt/ele choke wire for fire safety.
http://vb.foureyedpride.com/showthre...Electric-Choke
http://vb.foureyedpride.com/showthre...Charging-issue

Eventually got rid of the whole deal. Always doubt if was open all the way or even was working.
Have a manual op choke now that works. When engine sort of bogs on warm up drive, time to adjust choke setting.
Learned to warm up engine before driving and if needed, coax cold warm up driveability via gas pedal and choke setting.
Alternative choke knob loc is way easier to use than on or under dash.

[at_the_junkyard]

For what its worth to the discussion I wired up a 6 VDC automotive relay to the stator wire on my 3G alternator to control a 12VDC source for the choke cap on my edelbrock carb. (Edelbrock does state it needs the full 12 volts for proper operation) The 6 volt auto relays are a bit of a rare animal but you can get them.

Wiring it this way with the relay will only power the choke coil when the alternator is spinning (motor running) and not when you leave the key on for a while. Not a big deal if you start your car right away all the time I suppose.

[burntorange84]

what carb you running? I'm running a edelbrock and it says do not connect the chock to the alternator, connect to a keyed 12 volt source.

Still sporting the stock 4180.......well it does have a few mods. It needs the lower voltage at the choke.

Spliced a small 5a fuse and holder to the alt/ele choke wire for fire safety.
http://vb.foureyedpride.com/showthre...Electric-Choke
http://vb.foureyedpride.com/showthre...Charging-issue

Thanks gr79. I think that might be a good idea to wire in a fuse.

-j

[graphicdesigner80]

Good luck getting it sorted out. Hit me up next time you make a junkyard run.