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My 70 is not charging and I need help to figure out the problem. Here's the symptoms:

I drove the car for the first time this season on Thursday. Had a 2 amp battery tender on it for about two weeks prior. The battery is an Optima with 880 CCA and is 2 years old. It had gone dead and been recharged twice over the winter. Things seemed fine on Thursday, started up great, guage showed over 12 volts at all times, with about 13 1/2 at hiway speed. Then after letting it sit for 24 hours it went completely dead. No lights were left on or anything else that might have drained it, (not even a clock in this car). After a jump start the guage shows only 10 volts at idle and will climb to 12 at 2500+ rpm. I drove it like this to the local cruise night but had to get a jump to get it home. Then at home I ran my tester from post to post on the battery and get only 8 volts. The alternator, (2 years old with 3k miles on it), was really hot to touch after only a 5 minute drive home. The alternator belt is OK and not slipping. This is a mainly stock system. Only mod is a small-body HEI in the OEM distributor.

I'm an idiot when it comes to electrical stuff. Can someone tell me how to identify the source of my problem? Did I fry the battery? Is the alternator shot because it was getting hot? Is the regulator the problem, (since it drained over night with no known draw)? Teach me, please!

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Bob Von Kaenel
70 SS 53k orig miles
 

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"Teach me, please!"
OK, it's lunch time anyway.

"Things seemed fine on Thursday, started up great, guage showed over 12 volts at all times, with about 13 1/2 at hiway speed."

Voltage is way too low. 12 volts is the battery voltage. Using the old "water pipe" theory, voltage is pressure, amperage is amount of flow, and ohms (resistance) is drag or restriction. In order to charge any battery, the charging voltage must be higher than the battery to "push in" the amount that has been taken out. Too little voltage, it won't go in. Too high, it damages the battery. What you need is around 13.5 - 14.5 volts at idle. Otherwise you are not charging the battery.

"After a jump start the guage shows only 10 volts at idle and will climb to 12 at 2500+ rpm. I drove it like this to the local cruise night but had to get a jump to get it home."

Battery is not being charged. With the car running at idle, measure the large red wire (B+) on the back of the alternator. Measure it to a good ground. You need a reading around 13.5 - 14.5 volts.

"Then at home I ran my tester from post to post on the battery and get only 8 volts."

I'm assuming this is with the car off. Battery is obviously low, not being charged. Car batteries don't like to drained down and charged back up many times. It may be OK after the real problem is fixed but may not be.

"Did I fry the battery? Is the alternator shot because it was getting hot? Is the regulator the problem, (since it drained over night with no known draw)?"

Take the measurement off the back of the alternator with the car idling. That gives you a starting point. Suspect it will be low. Have someone like AutoZone check the alternator for you. If they say it's good (assuming they did a good job, hard to tell about some places) swap the regulator out and see if the alternator voltage come up. Be sure to disconnect the battery when installing or removing any item.

Once the alternator output is corrected, get the battery charged up with a charger, and keep an eye on the battery and see if it stays up to 12 volts over a few days. I don't trust these chain stores with their battery checks.
 

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Discussion Starter #3
Thanks John! Good info.
 

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One thing that would make me think bad thoughts about the alternator is the fact it was getting hot. If it's not charging, it's not doing any work so it shouldn't get hot. Disconnect the big red wire from the back of the alternator and see if it sparks when removed. This is car off with battery connected. I'd wonder if it has a shorted diode. That would explain the battery drain and the alternator not working at the same time.

John, I wouldn't think you'd see even 13.5 volts at idle with a mechanical external regulator. It just seems to me these things don't work at idle. I just threw an internally regulated alternator (67A one) on my car and get 14.2V at the battery all the time, with any rpm, and with all normal loads. Much better than before.

Peter
 

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<BLOCKQUOTE>quote:</font><HR>Originally posted by Peter F.:
John, I wouldn't think you'd see even 13.5 volts at idle with a mechanical external regulator. It just seems to me these things don't work at idle. I just threw an internally regulated alternator (67A one) on my car and get 14.2V at the battery all the time, with any rpm, and with all normal loads. Much better than before.

Peter
<HR></BLOCKQUOTE>
Just a starting number Peter. Below that I wouldn't expect it to do anything. I run about 14.7 off my 64 with the external Wells unit installed. No plans to switch to an internal. It's a numbers matching case.
 
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