Need electrical advice

Texas Tom

Texas Tom

Senior Member
Hope you guys can give me some advice regarding an electrical issue with my '31 coupe.

This morning the 12V battery was a tad low, so I charged it.

This afternoon the car started and ran fine. But the horn works only when the engine is running, and the lights never work. Also, the needle on the amp meter on the dash doesn't "flip" to the right when I first start the engine and rev it. The needle is just barely right of center and won't move (it just quivers a bit).

Does all/any of this point to a bad alternator?

Thanks for any advice you can offer.
 
if you have a multi meter check the voltage output of the alt while running and also the batt when the car is not running. Sounds like it's not charging.
 
Sounds like a bad alternator to me, but I guess is could be a bad connection. One quicky test is to put the blade of a screwdriver next to the bearing on the toward-firewall end. If it's working, with the motor running, the blade should be magnetically pulled against the alternator. If you have a multimeter, there should be a few volts OVER 12V between the main output connection post and ground. Be sure you're set to DC volts.

Why mess around? Take it out and take it to an auto electric shop. Be sure to tell the nice man whether you are positive or negative ground.

Steve
 
One wire alternators usually do not charge on start up and need some good revs to start charging. Does it charge later while you are running? If so, it is probably normal. Once it starts charging, it will charge even at idle. Should put out over 13-14 v. As for the lights, they should work off the battery even if the alternator is not charging. You may have a wiring problem there.
 
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