replace the alternator?

[bajaherbie]

last night i drove the 73 for the first time in the dark.... just from the driveway to my shop building though! as soon as i turned on the lights the car would die, turn them off, start car and repeat.... today i checked with a voltmeter the battery terminals with the car running, 11.8 volts. a bit of internet search says it should be 13-14 volts. does my alternator need to be replaced? 50 or 65 amp?                 thanks for the help, 'herbie

[Paul G]

At idle rev the engine up a little and watch the battery voltage, what does it do? Should be close to 14 volts. Again at idle, check the voltage output from the alternator stud on the back of the alternator, rev engine, what does it do? Should be 14 volts. To verify alternator output, disconect the battery neg terminal with the engine idling in park, dont blow your self up! Engine should stay running on alternator power alone. If it does not, the alternator or regulator could be bad.

Check the battery terminals for clean and tightness. Check the neg cable at the block and the small wire conection to the body. Your alternator belt could be loose, idle speed too low, battery weak or dying.