Hi everyone, its been a while since iv'e posted here. Today i went to start my dad's 89 vette. When it cranked it cranked a bit slow but its because it had been sitting for a month.

After it started i noticed a humming noise coming from the engine but it was really low this noise that i didn't take notice of it as i thought it was my ears playing tricks on me.

So i left it idling and went to do something in the other garage, after 5 minutes i go back and again there was a faint humming noise, i looked at the engine bay but i couldn't find were it was coming from. Then i went to turn it off and saw that the dash was really dim, so i checked the voltage and found it was 9.6v! So i turned the engine off. Then tried to restart it and the starter just clicked without turning. I hooked up the battery charger and left it for an hour.
After that i started the engine but the voltage was 11.1v and it was getting low 10.7, 10.5 etc after 2-5mins.

I checked the battery voltage with a multimeter and it was almost the same as the gauge on the dash.

How can i check the alternator without removing it from the car to see if its charging or not?
Could the humming be related? Maybe something in the alternator broke?

Quote:

Hi bogus!

Thanks for the reply, tonight i will let the charger charge the battery and check it tomorrow morning, if its dead which probably it is i will remove it and take it to a good electrical shop to see if it can be repaired.

99% of the time, an alternator can be rebuilt. The only problem is if the windings on the armature get torn up some way.

Brushes, diodes, regulators... all replaceable, same with bearings.

I would agree with Andy. You can check it at home, but an electric shop will test it free. The C4s are notorious for eating up alternators.

http://easyautodiagnostics.com/altern ... or_diagnostic_tests_1.php

Also, charge the battery fully before the engine is started and ran with the replacement alternator. A alternator is not designed to charge a battery, only to maintain it while running.

Joel

Joel is right... But to put a finer point on his comment, the alternator is designed to recharge a battery after losing 1% during start-up... then running the car... that's it...

The battery is outside the the loop, so to speak, of regular operations.

Hi guys an update about the no charging issue.

I took the alternator to an auto electrician and he replace the rectifier and both bearings, i installed the alt back all was well for just 10 miles as the battery light came on and the voltage dropped to 11v. Checked the alternator again with the multimeter and with the engine running i was just seeing .6v. I removed the alternator again and took it to the same elctrician and later that day he called me to tell me that the regulator needed replacing. So he replaced it and i installed it back and for now everything is ok.

Glad it is back up and running!