Charging trouble on my '76

[Chris'sZ]

I got in today for a ride and she barely turned over and started. Volt meter showed 12-13 but rapidly fell. I shut her off and waited about an hour and then tried again but to no avail...wouldn't even try to turn over. Battery and alternator have recently checked out to be o.k. Any Ideas would be appreciated...

Chris

[76Datsun280z]

Obviously, the battery isn't charged up enough to give it enough cranking amps to start it. When was the last time it was started it? If was real recent that it was running and charging fine, it sounds as if you have a short that's draining the battery possibly while it was sitting. If it's been sitting a while and hasn't been ran for say a month or so, it could just be that the battery is just low and needs to be charged.

[Chris'sZ]

Thanks Car Guy...

I've put about 200 miles on her in the past week, with out any problems...???

Thanks for your in put.

Chris

[SteveJ]

I got in today for a ride and she barely turned over and started. Volt meter showed 12-13 but rapidly fell. I shut her off and waited about an hour and then tried again but to no avail...wouldn't even try to turn over. Battery and alternator have recently checked out to be o.k. Any Ideas would be appreciated...

Chris

Here is one way to diagnose the problem:

1. Check the voltage on the battery with a voltmeter (not the guage in the car). If it is above 12 volts, inspect your fusible links.

2. If the voltage from step 1 was low, charge the battery fully and try to start the car. If you have the same symptoms, it's the battery.

3. If the car starts and runs, measure the voltage with a voltmeter (not the guage in the car) across the battery terminals and on the cables running to the battery while the car is running. They should be approximately the same and in the 14 to 14.5 volt range. If the voltage is lower on the terminals than on the cables, you have a corrosion issue (Of course, clean the terminals and cables.). If the voltage is low on both, there is an issue with the charging system.

4. The early Z cars have adjustable voltage regulators, but your Z does not. Refer to a factory service manual for checking the function of your voltage regulator. If the regulator passes the FSM tests, it is possibly the alternator. I have seen a parts place "test" an alternator and say it is good when I knew it wasn't, so I always take those "tests" with a grain of salt.

Note: Conventional wisdom says that if you have a problem with the alternator or regulator that you replace both. I have replaced the voltage regulator without replacing the alternator with no ill effects. However, later I upgraded to an internally regulated alternator a few years later.

Steve