alternator won't charge

[earthman]

Here i go again. Common Delco 3-wire alt in the Model A, original 4 banger.
Has been tested 3 times on the testers at auto parts stores and passes every time. Installed on the car with good ground,13 volts in the battery, battery wire to battery (B), energizer wire connected to battery (field term 2), even idiot light hooked up.
Start the motor and rev it up, the idiot light does not go off, the ammeter does not show charge. The ammeter shows discarge when the fan or lights are on. I have insurance, a 30 day temp tag and i want to go race some VW bugs! Makes no sense, any help appreciated.

 

[Lightning]

Using a multimeter, check the out put at the alt., with it all hooked up and engine running - then check the out put at the regulator. If it's working on the test stands, it's got to be in the regulator.

 

[CR55]

Does the battery get low on volts when you run the car with the idiot light on? May be just a bad connection with the light....CR

 

[fuzz]

Connect the battery wire from the alternator to the main feed at the fuse box not to the battery. Regulator needs to read a draw from all circuits when you turn on fan and other accesories. It can't do that if the battery wire is hooked directly to the battery. Disconnect the idiot light wire at the alternator then read the ammeter. If it now shows charge you have a short in the idiot light circuit.

 

[Grumpyoldman]

Did you try to remove the filed and idiot light wires on the alternator and just hook a short piece of wire one end to the sensing terminal (#2) and the other to the battery terminal on the alternator. This is how they make a 3 wire into a 1 wire alternator.(without the idiot light wire hooked up) you can hook it up this way just to see if it'll charge.

 

[fuzz]

Here's some good info about hot rod wiring...
http://www.madelectrical.com/electrical-tech.shtml

 

[earthman]

Thanks Cr,Fuzz and Lightening. I should have stated that it has an internal regulator. The ammeter and idiot light are telling the truth,the motor dies if i pull the ground cable off the battery.

 

[earthman]

Yep, tried it that way Grump. Thanks

 

[dogpatch1]

e-man check continuity/resistance accross the amp gauge? ive had them where the needle moves to discharge but only because a few windings inside were still making enough contact to move the gauge but not enough to let full charge go thru. dp1

 

[Grumpyoldman]

Try running a new wire from your battery to the battery post on the alt. and then hook it up as a 1 wire and see if it charges...

Do you have the charging system running thru a fuse box? It could be a blown fuse or a bad relay for the charging system...

 

[Lightning]

Well, it may seem stupid - BUT - if the engine dies when ya pull the neg. off of the bat. and ya say it checks out on a test machine, do you have a good ground from the engine to the frame ? I say start it up and test it with a multimeter yourself, and check all the + side of the guages for continuity from + to + and + to -, it sounds like ya got a short or broken wire in the + side of your charging circut or a bad ground.

 

[dogpatch1]

or do you have a loaner alt you could sub out just to check...

heres a pic of how i wire em dp1

 

[Sniper]

A quick test should get it narrowed down, so you will know where to start looking. With everything still installed, and hooked up, take a look at the back of the alt. Should see a small "D" shaped hole around the outer edge, it will line up with the regulator. Start the engine, and with a small screwdriver or ice pick type tool resting on the case in the "D" hole, slide it in to touch the back of the regulator. If the alt is good, it will go to full charge, about 16 volts, you only need to do this for 3 or 4 seconds. All you did was bypass the regulator. If that worked, the regulator is bad, if there was no change, the the alt is bad. I'm guessing a diode in the bridge or trio. Removing the battery cable (or a bad ground) when running can produce a voltage spike and wipeout diodes in a flash. First step narrow it down. 2nd step, depends on what you find in step one. Sniper

 

[earthman]

It is awesome to have you all take the time to help. I appreciate you big time.
Here is how it stands now. A multimeter shows it putting out 13-14 Volts if the #1 terminal (idiot light) is connected to a positive source!!! Too weird, haven't checked yet to see if the #2 field term works as an idiot light. The cheap chinese ammeter never shows a charge,only varying amounts of discharge depending what is turned on.(note to self pay more and get better quality gauges). Now today the A sputtered, backfired and quit on a shakedown trip around the block and the problem seems to be a worn out distributer. Probably why they stopped driving it when they parked it many years ago in Hermisillo Mexico. So the distributer goes to the front burner and i will have to comeback to the alternater. Thanks again for
your help.

 

[Grumpyoldman]

Hey Earthman,

How did you make out on the distributer? Is it fixed?

 

[earthman]

Well thanks for asking Grump.The electronic ignition is on its way,will be here
soon.Could have put bushings in the distributer for a few bucks but this electronic kit will make it run better than it did when it was new.