Alternator Wiring

I'm not sure if the alternator is bad, or if I have the wiring wrong. Shouldn't there be a large wire coming from the big lug on the back of the alt., to the solenoid? That's what would bring the juice back to the battery and keep the engine running, even when there is no battery.

As it stands now, that's the way I have it wired, and the Jeep will shut off if I remove the battery cable. I have tried revving the engine (self-exciting), before removing the battery cable, but there's no change in the outcome...

I even tried the test light directly on that large lug, and there is no power coming out.

My only other thought is that the voltage regulator could be bad. Would this stop the alternator from charging?

TIA!

EDIT: I know there are reports of people getting shocked and/or killed by removing the battery terminals with the engine running. I do not condone, nor endorse this activity. YMMV

 

Tim what kind of alternator do you have? Is it a true one wire? Or do you have a plug for some wires to plug into. If you have a plug, then you will may need to send some voltage to the alternator to excite it.

Have you checked the voltage with a volt ohm meter?

I just changed out the old 6 vlot generator with a 12 volt alternator. Hooked it up and she worked great. Then I blew out all my new 12 volt bulbs when I tried it out at night. Boy they were ever bright :>) Going to take my alternator back to the parts store to see if it has a bad internal regulator.



I have converted several jeeps and old tractors with rebuild alternators and this is the first time I have turned my lights into flash bulbs.

 

This is not a one-wire. It still has the external voltage regulator that bolts to the fender.

I just noticed last night that the back of the alt actually has 2 threaded lugs. I didn't check the other one, to see if it has power coming out... Maybe it does, that that's where the wire running to the solenoid should be attached.

 

Tim
I don't consider myself an expert on wiring alternators. However I would suspect one of those wires from the plug needs to be energized to excite your alternator.

A good place to get 12 volts is from the + side of your coil or on the accessory side of your ignition switch. (The downside of hooking it up to your coil, is that your alternator might put out some voltage and not allow your motor to stop when you turn off your key.) It works ok on my jeep. Sometimes it works and sometimes it doesn’t. You could also probably find a wire under the hood that is hot only when the switch is on. You can find this with a test light.

A quick simple test to see if your alternator is putting out is to hold a screwdriver against the back of it when the motor is running. It should be magnetize and hold your screwdriver against the alternator. Do this with one of those wires on the plug energized, and then test again when it is not. See if this does not turn on the alternator.

 

Tim, is it a Motorola alt ?
if it is, looking at the rear of the alt, with mounting tabs in 12 o'clock/6 o'clock position, the output terminal is the top right terminal, the other large terminal is the regulator terminal, middle of alt, under output terminal (these are threaded studs); the bottom two should be flat blades, with the vertical terminal being the ground and the horizontal the field terminal.
Note: the regulator terminal is to be used for field excitation only and not as a source for lights or accessories per the FSM

 

it also looks to me that the excitation wire might be a gray wire coming from volt regulator.
if you have re-wired of course, that's different

 

Thanks Jim and Cliff.

This is a Motorola alt. I think I might just have the wiring a little off... I'm going to work with it a little more tonight.

If I don't come up with something, I'll post some pictures.

 

Cool - will do...

Thanks Billy!

 

Sorry Billy. Just a little more head-scratching and I had it figured out...

The alternator was just bored. I had to excite it via the gray wire that Jim mentioned above.

Thanks for the help guys!!!

 

Glad you got it working.

 

Sorry Billy!

I appreciate the effort though!