Electrical system NOT showing a charge?

spirockp · Dec 7, 2006

History: 66 Mustang V8 Coupe, hasn't been on the road in 11 years. I have had it for 4 years and I just got it on the road last weekend. I completely rewired the car using Painless. When turing on the key I show 12 volts. With the car running I also show 12 volts. After driving the car around the volts slowly drop down and I have to put a charger on the battery over night to charge again. I have had the new alternator tested and it is fine. I changed out the voltage regular and I purchased a new battery, because the battery I had was old and it needed to be replaced anyway. I have checked the wiring 3 times and yes everything electrical works perfectly. The wiring is complete from front to rear and I have no other issues.

So my question is how do I start testing next? What do I test? How do I test? Any ideas would really help.

Thanks.

Peter S.

67Dylan · Dec 7, 2006

It sounds like the battery is not charging. You should see well over 12v's when the car is running. I usually see between 13.8-14v's w/the car running. Have you had the alternator checked while in the car or out of the car?

spirockp · Dec 7, 2006

Correct, on my other car I also show 14 volts when running.

I had the alternator tested out of the car. That's my question, how do I test it in the car? It is not a one wire alternator.

2nd Mustang · Dec 7, 2006

Where are you checking for the voltage while it's running? If the alternator checks out good, you should be getting 13-14 VDC right at the positive battery terminal. If not, the charge isn't getting to the battery. Electrical gremlins suck.

spirockp · Dec 7, 2006

2nd Mustang, that's my question. Where do I test the voltage coming off the alternator? I have an electrical tester, just don't know where to start.

5.0ina66 · Dec 7, 2006

Put a voltmeter on the S terminal of the alt with the car idling, and hope for 13-14.5V. It really has to be closer to 14 though, my 66 Fury reads 13.4 and charges poorly.

spirockp · Dec 7, 2006

5.Oina66, I will test that tonite.

The next question is, what do I do if it is reading 14 volts and what do I do if it is not reading 14 volts? I'll also check the reading at the battery.

Thanks.

67Dylan · Dec 7, 2006

spirockp said:
5.Oina66, I will test that tonite.

The next question is, what do I do if it is reading 14 volts and what do I do if it is not reading 14 volts? I'll also check the reading at the battery.

Thanks.

You mentioned you have already changed the voltage regulator, are you sure it is installed correctly and everything tightened down? If you want to verify the charging system while the alty is in the car, you can take it to an autozone or checkers. They check it for free.

Check all your connections, positive and ground, ensure they are tight. Make sure the batt terminals are clean. That is about it. Betting it's the alty causing your problem.

2nd Mustang · Dec 7, 2006

I seem to remember that the voltage regulator's body itself needs to have a good body/frame ground too, if it's the original equiptment type.

Also, how old are both battery cables? They may look good on the outside and have continuity, but old cables sometimes do not have enough capacity internally to let the full charge get to the battery. Do the battery cables seem excessively hot while the engine is running?

66Runt · Dec 8, 2006

Start by making sure you have all the wires run correctly

Here is a link to a schematic:

http://hammar.dyndns.org/~djhamma/wiring/wiring1966.htm

Then make sure you have the proper voltage to the correct points at the right time.

I'd suggest doing a search on this site, going to the library and looking through a Mitchell manual, or picking up the factory manual.
It's an easy job to check the charging system. but it's more writing than I'm going to do.

Good luck,

spirockp · Dec 8, 2006

66Runt, that's a good site. I have seen that schematic in my Haynes manual and I noticed that it's alternator setup is different than Painless. I then looked again at Painless and they have 2 different ways of hooking up the alternator to the voltage regulator. I will be calling them soon to ask them why.

I'll keep you posted.

Thanks.

spirockp · Dec 8, 2006

OK I called up Painless and they said to test the alternator just jump the A and the F terminal on the regulator and see if it gives off a charge. Now remember I have mine wired as painless states, not like the orginal setup. They said if that works then wire it up like the orginal setup, which is Painless's alternate setup? Not sure why they have it in the book two different ways.

I'll let you know what I find out.

spirockp · Dec 11, 2006

Problem solved.....

Long story short is that my hot lead to the voltage regulator was bad. So I was not powering up the voltage regulator so it couldn't tell the alternator to charge. Once I gave it a good hot lead everything work fine.

Peter S.

By the way as only a test, you can by-pass your voltage regulator by connecting a hot lead (12Volts) to the F (or field) terminal to your alternator and it should give off a charge. However you can only have it that way for 5 seconds or so because your alternator will give off it's highest charge and burn itself out and other things as well. Mine showed 16 volts with that test.

66Runt · Dec 11, 2006

Great job

Thanks for taking the time to follow up. Hopefully this will help someone else in the future.

So what are you going to spend all your time on now that you won't have any more wiring problems to plague you?

spirockp · Dec 12, 2006

I will now be focusing on my rattling exhaust, and why my C4 trans is not going into 3rd gear.

Again, it has only been on the road for 2 weeks and I have about 30 miles on it. I'm bound to find items to play with.

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