[sarah]

I just finished rebuiling the engine on my 66 and am working out all the little kinks. But my battery won't recharge. The battery and the altenator are new. maybe its wired wrong or i just dont know and the book is confusing

[pyro1730]

welcome to the site. congrats on the rebuild. Unfortunately I don't really know what to do about the battery. It's possible you could have a bad or miss-connected wire. Does the car start off of a jump? Another thing to check would be to see if all the wires are connected to the alternator properly. Also there may be a short somewhere in the circuit. I'm sure someone on this site will be able to help you out more. Good luck

[BRENSTANG03]

welcome to the site,try the wires that connect to the starter?

[jim293]

Sarah welcome to AFM. Good luck with the problem.

[stlwagon]

Welcome. Let's look in here.

[MIL1ION]

Sarah, just take the battery to a parts house and have them test it.

batteries can develop shorts inside themselves and they can also sulfate and become useless.

[rodbender]

While your at it check your voltage regulator too.

[sirtwig]

Try this trick, start the car and let it run. While running, remove one of the battery cables. IF the car is still running with the battery disconnected then you know the altenator is working. If it dies then start looking at the alt and wiring.

[MIL1ION]

That's a good way to destroy an alternator. It will ruin the diodes

You can achieve the same thing by revving up the engine with all the cables connected .

I say the battery is pooched

[sirtwig]

Have not harmed one Alt yet doing this, especially if you remove only the Neg cable.

[MIL1ION]

One should never remove a battery cable from the battery with the engine running.

Mechanics used to do that with GENERATOR systems (DC) to excite the generator to start charging.
Alternators make AC current and rectify it to DC

Why take the chance when it can be tested without risk ?

[MIL1ION]

the battery is a constant load for the alternator... to slow down the reaction of the alternator... when you pull the cable off... the current has no place to go so the voltage builds up before the voltage regulator can control it...

the diodes in most alternators are rated at 25 amps at 100 volts PIV.... (peak inverse voltage..). when you go over that voltage... the diodes are damaged.. electronics are cooked... the alternator will usually have a much shorter life...

with a test light... test the output wire on the back of the alternator for voltage... then test the large red wire that plugs into the side of the alternator.. those are wired through different fusable links on the top of the starter solenoid...

[mwillis]

Take the battery to a parts store to have it load tested.
To test the alternator and regulator: Test the voltage of the battery with the engine NOT running. Should be less than 13V, about 12.7V for a charged battery. Then, start the engine. Check the voltage at the battery. It should be about 14V.
Mike

[Veronica]

Hello. It could be that the battrey is no good, but, it could also easily be as you suspect, and the alternator isn't wired up correctly. A common culprit is the ground wire, but, it could be other things also. Here's how the alternator should be wired up.
The Care and Feeding of Ponies: Alternator and charging system