I have a 69Z28 that has a charging problem. When I put on my head lights my amp gauge goes South on me. I have replace the altenator and external regulator and I still have the same problem. Yesterday the bat went completly dead on me and I pulled it out and had it checked out. It had a short so I thought I had found the cause of the charging problem. I put in a new bat and I still get a neg reading when I turn on my lights.
Any ideas would be a big help to me.
Schoon

Did you fully charge the new battery before you installed it? Have you checked all the cable and hot and ground connections to make sure they're clean and shiny?

You should check the connectors at the regulator, battery, and alternator and make sure that they are secured to the wire without any corrosion.

It's a pretty simple circuit. You should be able to use a volt meter and measure the voltage at the output of the alternator and trace it to the regulator input to check the alt and wiring. Then check the reg output. If it's lower (same as battery), then the reg may be bad.

One other thing - if your battery was shorted and you ran the new alt/reg, it's possible that you burned out one or the other if you ran it that way too long.

I would do some further testing of the system. Disconnect the hot lead from the battery and put a volt meter between the lead and the positive terminal. The hot lead on the tester should go to the battery cable and the negative lead of the tester should go to the hot lead (positive) post on the battery. You should see a minimal draw, maybe two volts or so. If you see a higher draw like 10 to 12 you have a short or something on somewhere. First start with the diode on the alternator. Disconnect the alternator leads and see if the voltage draw drops. If not reconnect the alternator and start popping fuses out one at a time and see if the draw stops. When you find one that lowers the voltage draw then you know you have an issue with that circuit.

I had similar problem a couple of years ago. Turned out the main wire to alternator was mostly broken.

You should use a volt meter on battery to check with engine running. You should see right around 14 volts, even with lights on. The amp gauge is too difficult to get accurate reading.

Check circuits for shorts, as others suggest.

Hi,
Good point, I didn't have a full charge when I put it in. I will try again tomorrow.
Also, please do me a favor, start up your Z and turn your lights on. Does your gauge read neg at all. Does the gauge read positive if you rev the engine with the lights on?
Thanks in advance
Schoon

If the car is all stock and no add on electrical accessories the amp gauge should never read neg with the engine running at anything faster than idle. When the amp gauge reads neg with the engine running, it means the electrical load is greater than the alternator output and the battery is not charging, you are just running off the battery. Original Z28s had a larger than normal deep groove alternator pulley and the charging system was marginal at best at idle with the lights on. When mine was all original it would sometimes read neg at idle with lights on depending on the idle speed. it always read positive at anything above idle. To answer your question, if the car is 100% stock, yes it would read neg at idle sometimes with the lights on, never without and never at anything faster than idle. If you do not have the factory larger deep groove alternator pulley, then it should never read neg with the engine running.

Thanks that is good info. My car is not stock anymore and the pullies are made by March. I quess the problem I have is when I rev the engine the amp gauge does not move. Today I will put another bat in along with a new external regulator. If this doesn't work the only thing left is the altenator. If I need to replace the altenator and that doesn't fix the problem I stuck!

Thanks that is good info. My car is not stock anymore and the pullies are made by March. I quess the problem I have is when I rev the engine the amp gauge does not move.
The amp gauge is not supposed to move normally when you rev the engine. With the engine running and a fully charged battery, the gauge should read slightly pos, when the battery is real low it would read medium pos. With the engine not running and lights turned on it should read neg, and the more stuff you turn on the more neg it would read. The gauge only shows if power is going to ( charging) or from ( discharging ) the battery. Since the car isn't stock anymore, convert to a internally regulated alternator, see here. http://www.chevelles.com/techref/ftecref14.html
If you are still having discharge problem or low voltage it could be a crank to alt pulley ratio problem, see here. http://www.powermastermotorsports.com/power_pulleys.html
Also install a voltmeter, they are much better at monitoring the electrical system then the factory amp gauge, see here
http://www.autometer.com/tech_faq_answer.aspx?sid=1&qid=5

Thanks for all the info. The pully ratio sounds interesting.

Just to let you know I finally fixed my charging problem. It turns out that the Bat caused all my problems. Because of the short it had it blew out my altenator and regulator. Every diode in the altenator was blown.
Thanks again for your help.