Alternator help

[hudlow]

I've got a little probelm with the electrical system on this old Jeep truck (pictured left) that is beginning to get me riled up.

First, I know my alternator is good. It's been tested several times. I've tried 2 different Voltage regulators and get the same results.

Here's what's up...My battery is losing it's charge overnight. The truck will not crank in the a.m. after I park it for the evening.

There are two wires coming off the back of the alternator. One is the big wire that charges the battery. The other is a smaller wire that goes to the voltage regulator.

1.) I have figured out that if I unhook the smaller of the two wires from the alternator when I park it for the evening the battery will not die overnight.

2.) If I do not hook this wire back up when I crank the truck the next day the alternator does not charge the battery and also the ammeter does not work.

I know this smaller wire reads to ground but for the life of me I can't find the short.

It's driving me nuttier.

I have figured out a work-a-round. I've bought a relay that I'll put in line with the smaller wire that I'll run through a set of N/O contacts and energize the coil when the truck is running. Then the contacts will close and the smaller voltage regulator wire will charge the battery and the ammeter will work. When the ignition is turned off the contacts will open back up and stop the battery drain.

I'd rather fix the problem instead of putting this relay in.

Does anyone have any ideas?

I thought about putting 110v. to the wire just to see where the smoke came from and find my short that way.....but I was real mad and slightly drunk at the time I'm not going to do that nor do I advocate anyone else do it, although.....

Any suggestions or condolences will be appreciated.

hud

 

[DieselPower]

For starters do you have a multi-meter?

 

[hudlow]

For starters do you have a multi-meter?

Yes.

hud

 

[randy41]

this aint gonna help you but my son had an old crown vic and he had to disconnect the negative terminal after driving. we tried to find the cause to no avail. he sold it for a little cash and an electric guitar.

 

[hudlow]

this aint gonna help you but my son had an old crown vic and he had to disconnect the negative terminal after driving. we tried to find the cause to no avail. he sold it for a little cash and an electric guitar.

For an old Les Paul or Strat I might let this Jeep go......

hud

 

[Jimbrown]

Wild guess but. Alternators have to have diodes somewhere in the line to rectify the AC to DC. If one of those diodes is going bad it will allow the curent to flow back into the alternator. So the alternator may check good and produce current but a bad diode will short to ground.

 

[hudlow]

Wild guess but. Alternators have to have diodes somewhere in the line to rectify the AC to DC. If one of those diodes is going bad it will allow the curent to flow back into the alternator. So the alternator may check good and produce current but a bad diode will short to ground.

Thanks for the guess and it was a good one.

I've had 3 different alternators on this truck and I'm hoping my luck isn't bad enough that the diodes were bad in all 3.

I guess to be sure I could physically remove the alternator from its mounts and see if I read voltage from the alternator casing to ground?????

Thanks,

hud

 

[BillyP]

Wild guess but. Alternators have to have diodes somewhere in the line to rectify the AC to DC. If one of those diodes is going bad it will allow the curent to flow back into the alternator. So the alternator may check good and produce current but a bad diode will short to ground.

I ran into that very problem on a 71 Ford LTD. As soon as you turned the key off, the alternator light would come on. Start it up and the light would go out. Bad diode.

 

[gator]

Had a problem like that on a 73 Ford F100 P/U. Ended up being the old points type voltage regulator had a couple of contacts stuck closed. Father in law mentioned to check if idiot lights on dash and gauges still register after key shut off. Sure enough did and after replacing voltage regulator no more dead battery.

 

[czechsonofagun]

There are multimeters capable of meassuring the current. I got mine from sears and it has the claw to clamp on the wire to see how much runs in it. I would get one of those and check where the amps are going over night.

Maybe a big strippers party?