Charging issues - Chevelle Tech
Electrical & Wiring Troubleshooting electrical problems.

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post #1 of 10 (permalink) Old Jul 1st, 18, 2:29 PM Thread Starter
 
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Charging issues

I have a 1969 Chevelle SS. It has HEI ignition. I am having charging issues. Took the alternator in and had it checked and it check OK. Did several test. The worst it did was 13.4 volts and the highest was 15.2 volts. My cars gauge says 12 volts when running. if I turn on the head lights it goes down to 10 volts. When I check with multi tester at the battery with car turn off it reads 12.2 volts. It reads the same 12.2 volts when running?? What would cause the alternator to read 13.4 plus when on tester and seemingly charging correctly and not showing that it is charging when hooked up in car?? I am really confused here.

Last edited by davewho1; Jul 2nd, 18 at 12:38 AM. Reason: title sp.
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post #2 of 10 (permalink) Old Jul 1st, 18, 2:41 PM
rkd
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Ron
 
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Re: Charging issuse

I have a 66 with a separate regulator, if your 69 has a separate regulator, that may be the issue. They are cheap to buy and easy to change. Also make sure the terminals where the wires plug into the regulator are clean and make good contact. If you have an internally regulated alt, the rest of this also applies.

Check each and every battery connection, ie, the pos and neg at the posts, and the connections at the car for both pos and neg. Clean and tighten. Make sure the actual cables are solidly connected to the molded lead posts. I have experience in this....

Make sure the connections at the horn relay and dist block are clean and tight. Those on my 66 are prone to getting rusty and have to be fixed now and again.

Make sure you have a good body to engine ground ie, ground strap. Typically the braided wire at the firewall.

You did not say if the car was having starting issues. Let us know.

66 Malibu Coupe, home rebuilt 350. Took me 39 years to get her!
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post #3 of 10 (permalink) Old Jul 1st, 18, 3:18 PM Thread Starter
 
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Re: Charging issuse

e

Thanks for the reply. I went and got a new alternator and above is the results. So I got and alternator for a 69. In 69 they had the external regulator. My car does not have a regulator. So now I think I have the wrong alternator. But I was thinking that the two different alternators had different style plugs? I do not have a one wire alternator. It has the battery 8/10 gauge wire going to the battery connection. Then a two wire plug that is more square then long and flat. Is there a difference in plugs on alternators?
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post #4 of 10 (permalink) Old Jul 1st, 18, 4:01 PM
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Re: Charging issuse

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Originally Posted by Cper View Post
e

Thanks for the reply. I went and got a new alternator and above is the results. So I got and alternator for a 69. In 69 they had the external regulator. My car does not have a regulator. So now I think I have the wrong alternator. But I was thinking that the two different alternators had different style plugs? I do not have a one wire alternator. It has the battery 8/10 gauge wire going to the battery connection. Then a two wire plug that is more square then long and flat. Is there a difference in plugs on alternators?
On the two wire connector, on an externally regulated model, the plug exits out the back and are in a II configuration while the internally regulated ones are in a -- configuration.

In this article is shows a picture of the two wire connector location and how they are different (the one on the left is internally regulated while the right one requires the external regulator):

Alternators for GM Cars Charging Ahead - Hot Rod Network



Who knows but someone might have changed the plug end designed for an external regulator to plug into the alternator and then swapped in an internally regulated model plug housing. If they did so, they also needed to have jumpered the old external regulator plug so the alternator gets the proper signals for it to actually work.

Jim
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post #5 of 10 (permalink) Old Jul 1st, 18, 7:46 PM Thread Starter
 
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Re: Charging issuse

Thanks again Jim for the reply. I feel a little on the stupid side here. I looked a little harder at the Chevelle after the plug differences and found that it dies have a external regulator. So I will just take it off and replace it as I know there not to expensive. Would a bad regulator cause the low voltage only 12.2 or .3 at the battery when car is running? I was told that it should be around 13 or a little higher when running and reveed up
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post #6 of 10 (permalink) Old Jul 1st, 18, 7:50 PM Thread Starter
 
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Re: Charging issuse

One other question for you fellas? Should I run a separate ground wire from the small screw on the alternator that say ground on it to a good ground too? I just can't ever remember seeing that done before. Quess it's there for a reason but just want to make sure it would be ok.
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post #7 of 10 (permalink) Old Jul 1st, 18, 8:19 PM
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Re: Charging issuse

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Originally Posted by Cper View Post
Thanks again Jim for the reply. I feel a little on the stupid side here. I looked a little harder at the Chevelle after the plug differences and found that it dies have a external regulator. So I will just take it off and replace it as I know there not to expensive. Would a bad regulator cause the low voltage only 12.2 or .3 at the battery when car is running? I was told that it should be around 13 or a little higher when running and reveed up
Sometimes I can be looking right at something and not see it right away. It happens.

The regulator works with the alternator and if the regulator senses that the vehicle needs more power and the regulator does not have the alternator put out more power, then you can have low voltage issues and/or high voltage issues.

When I bought my 68, it still had the original alternator and external regulator on it and the first time I took it out at night I commented to myself, boy the lights are really bright for this old of a car and once I measured the voltage at the battery I found out why the headlights were so bright. I measured darn near 16.5V which explained why the bulbs were so bright and probably why the aftermarket radio was fried.

The external regulator also needs to have the proper signals sent to it before it can get the alternator to react properly so while you can throw new parts at the problem, there may be issues with the car that even with new parts will not get things to work right.

Recently there was some discussion about how the original regulators have the headlights going bright and dim so on my 68 I did some tests and never saw this issue but I did document things and the highest voltage I have had was right around 14.1V or so. The battery voltage before the testing was right about 12.6V. Even if I had a voltage of 13.6V across the battery while it was running I would be happy as from what I have read and seen, you need a minimum of 1V over the batteries nominal voltage so the battery gets replenished and keeps up with the electrical demands such as the headlights being on, the heater fan on,and so on and probably you don't want nothing much higher than 14.5V

As far as a dedicated ground from the alternator case to the battery, engine block, or the body of the car, sometimes this has to be done due to the coating on an alternator to where the coating prevents it from seeing a ground from it being bolted to the engine.

Jim

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post #8 of 10 (permalink) Old Jul 1st, 18, 9:40 PM Thread Starter
 
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Re: Charging issuse

Ok, so when I check voltage at the battery with car not running and running it reads the same. 12.2. Would a bad regulator cause this? The cars volt gauge shows the same 12 when running and then if I turn on headlights it drops to like 10 on the cars gauge.
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post #9 of 10 (permalink) Old Jul 1st, 18, 10:23 PM
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Re: Charging issuse

I'm thinking bad grounds with high resistance is dropping your voltage. Add a few supplemental temporary grounds and see if that helps.

Rick

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post #10 of 10 (permalink) Old Jul 1st, 18, 11:18 PM
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Re: Charging issuse

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Originally Posted by Cper View Post
Ok, so when I check voltage at the battery with car not running and running it reads the same. 12.2. Would a bad regulator cause this? The cars volt gauge shows the same 12 when running and then if I turn on headlights it drops to like 10 on the cars gauge.
If things were right, with the car off you would read the 12.2V across the battery posts but once running it needs to be above that and at least 13.2V across the battery terminals.

Here's how it is on my 68 when I did some testing a while back:

https://www.youtube.com/edit?o=U&video_id=eaFXqWSf5o4

You could have a regulator issue and/or a signal issue going to the voltage regulator, and/or even a ground issue. The external regulator needs battery voltage on one of the 4 terminals while a second terminal is wired to the GEN light in the dash. The other two remaining wires on the 4 wire connector go from the regulator to the alternator.

On my 68, on the battery terminal of the regulator, it contains a fusible link that can burn out or if it has a poor connection, then the alternator is not allowed to work right but just this one portion or connection of the regulator also has to work in conjunction with the signal from the GEN light in the dash.

A question I have, is when you go to start the car but just turn the key to the RUN position without starting the motor, does the GEN light in the dash glow and come on ?. If not, and if the bulb is burnt out it could prevent the alternator and regulator from working properly.

I will say, stick with using your meter under the hood on the battery. Using the indash gauge and how it reads is connected to a lot more wiring and connections than just under the hood with your test meter and you can get strange results sometimes using the gauge inside the car. Depending too on what meter you are using and how accurate the one in the car is, they may or may not match with the readings between the two.

Jim
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