Battery Drain - Alternator Issue?

[Vortech]

Ok, I replaced my 3 wire alternator and external voltage regulator with a internally regulated alternator. I installed temporary jumpers at the old voltage regulator, tied in 3 of the original 4 wires at the alternator, new alternator doesn't seem to have a ground location that the old alternator had. Now, my battery drains dead with ignition off. I tested by removing the positive terminal and placing a test light between the positive terminal and power lead cable. There was a light on until I disconnected the 2 prong wire from the alternator. Is the new alternator bad? Or did I foul up the wiring? Battery voltage is good and battery does charge.

[tincan1966]

I think maybe you have too many wires jumped.

With your jumper wires in place, do both wires(red and white) on the plug in at the alternator have 12v+ ? The white should only have power with the key on, and should be a bit below 12V+ if it has a "gen" light.
Using a volt meter is a better way of testing. A test light can light up with anything between 6 and 12 volts.
In the FAQ section there are several threads about wiring alternators. There are discrepancies as to which way is best, but they all seem to work.

The easiest is to run the red wire from the two wire plug to the "BAT" term on alternator. The white wire should go to the voltage regulator wire plug in. Seperate the wire harness from the alt to the regulator. With the key "on" find the wire that has 12V+(again, may be slightly less, since OEM uses the dash indicator bulb as a resistor) I beleive this is a brown wire. Splice the white wire to it.
Next take the original wire that was connected to the BAT on old alternator and connect it to new alternator. To clean things up, you can remove the unused wires between alt and regulator and remove regulator.
Some think there needs to be another wire run from alternator to battery, but we've found that to be unnecessary since the BAT wire runs from the alternator to the horn relay junction then straight to the battery.

Hope this helps you out.

[1963c-10]

Look at Sharps40's thread he did a great write up on the conversion.

[Vortech]

Ok, tincan66, tested the 2 prong plug at the alternator, red wire was hot at the alternator when ignition was turned on, white wire was zero, must be voltage sensing line. Still do not understand why alternator draws battery dead when it is hooked up. Must be a bad alternator??

[tincan1966]

If you have nothing on the white wire at the alternator, with the key "on" then it is not connected properly.

[Vortech]

according to all of the write ups, #1 on the alternator is voltage sensing , #2 is hot wire. I bought a standard GM plug from Oreily's. Should I switch these so #1 is hot and #2 is sensing?

[63ChevC10]

This is the one I used to convert mine. Maybe it'll help you out some.

http://67-72chevytrucks.com/vboard/s...d.php?t=119379

[tincan1966]

Originally Posted by 63ChevC10

This is the one I used to convert mine. Maybe it'll help you out some.

http://67-72chevytrucks.com/vboard/s...d.php?t=119379

That explains it about as easy as you can get, and will work great.

[Rich 5150 69]

When done wiring it all up you can test your alternator real easy....in my
opinion best and easiest way to test the diode block while the alternator is still on the engine is to do an AC ripple test with a digital multimeter. Just start up the car, turn on the headlights to remove surface charge off the battery. This will force the alternator to switch on. Next set the meter to AC Volts. With the engine running put the positive lead of the meter to the "BAT" terminal on the alternator and hold it there. Then place the negative meter lead onto the negative post on the battery. If you get a meter reading of more than 1.5 Volts AC (1 1/2 Volts AC) the diode block in the alternator is bad and needs replaced. Its a real simple test that only takes a few seconds to perform. Hope this helps!

[Vortech]

Well, Did the AC ripple test, .07 volts. Diode should be good. Going to un-bundle the wires next to see if there are issues hidden within. Still losing voltage. when hooked up to alternator.

[Vortech]

OK, Rewired according to the thread above, still voltage draw when connected to alternator. Very frustrating. Debating whether to replace already replaced alternator.

[tincan1966]

It is possible that there is another issue somewhere else. Depending on how it is wired, and there's several ways of doing it, It could be something like a stuck horn relay- that sems to be relatively common with these trucks, too since the relay is exposed to the elements on the radiator support. Try leaving the alternator plugged in and unplug the relay. it would be worth a shot.

these things are really hard to help with without being able to be "hands on" for testing.

[Vortech]

I'll give that a try 1st. Appreciate all of the help and advise

[Rich 5150 69]

Vortec, when you bought this aternator, is this new...? I`m begining to wonder if this is a one wire alternator...? I`m just grasping at straws here....!

[Vortech]

I bought the alternator at a swap meet from a vendor. Was new in box. Note, 2 prong plug on top was capped off leaving only the battery termination. I removed the cap and bought a GM 2 wire plug. Would this make a difference?

[Rich 5150 69]

Do a google search on GM one alternator wiring schematics, I am suspect you have a one wire aternator, which will wire up a little differant..

[tincan1966]

I would Google the part number on the box and see whatit tells you. If there was a cap over the plug in, I would think it could be a one wire, also. In that case, all you need is the wire from the "Bat" on alternator to the junction on the horn relay or go directly from the alt to the battery.

[Vortech]

Ok, problem solved. Disconnected all wiring associated with a 3 wire set up. Wired as a 1 wire system works great. Thanks to everyone who helped out. This forum is great.

[Rich 5150 69]

Cool Vortec, no wonder they had the terminals capped off...keep an eye on battery as far as overcharging, although should not be a problem, I`m just a three wire guy.....if you hadn`t read it, take a moment and read about the one wire units. http://www.madelectrical.com