Brand new alternator, Lights dim at idle, brighten on acceleration

10-24-2015, 07:44 PM
I just installed a new Bosche 125 Amp alternator about a week ago.

Puts out 13.9 to 14.0 at the battery with everything running at idle. When you rev the engine the head lights brighten for a moment then settle down to what might be considered normal. Battery holds at 12.6 volts over night and cranks no problem.

Only reason I replaced the alternator is because it is original and has traveled 280,000 kms already. Bearings were getting a little rough, although it seemed to be charging almost the same as the new one. (13.6 versus 14.0 for the new one).

Battery is 8 years old and has a 108 month 'life' to it, so should be replaced before winter sets in.

Could there be a problem with that screw on the back of the alternator referenced in a few posts, or is it possible that the battery is trying to say, 'I'm getting tired!'

11-10-2015, 08:45 AM
Answered my own question.

Battery died in the driveway on Sunday. Wouldn't take a charge. 113 months. Not bad for a 108 month battery.

Bought another at Wally World yesterday; - no flickering lights and a constant 14.5 volts at the terminals with the engine running.

Could be my imagination but when I replaced the alternator about a month ago I noticed that fuel economy increased. Maybe a hotter spark at the coil packs?


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