Shortly after starting the car, the alternator gauge drops to less than 12 volts and the idiot light comes on, then a minute later it's back up to almost 14 volts?
I have a new battery and I have tested both the battery (running & not running) as well as the alternator output while running. The battery tests out perfect but the alternator only shows about 13.4-13.6 volts after the motor has been running for a few minutes. Connections are tight and everything seems to work fine but the fluctuating gauge is what I can't figure out.
Thanks for any help.
07-20-2011 07:45 PM
07-20-2011 07:50 PM
Worn brushes in the alternator, or intermittent regulator, more likely the first.
07-21-2011 01:41 AM
I just bought myself a new regulator with brushes for my... eh, Volvo... And the way to see if the brushes are gone in that car is: all control-lamps in the instrument are on all the time!
07-21-2011 03:41 AM
loose belt maybe?
07-22-2011 10:05 PM
charging not charging
Belt tension is good, yes it is an internal regulator. I drove the car a bit farther distance this evening and the gauge fell to around 10volts and never came back. Just the last couple times I drove it, the gauge would fluctuate, tonight though, once it dropped down, it never came back up. I think you guys that mentioned the brushes may be correct. I'm going to take it in and have it tested and see what they tell me.
07-23-2011 07:12 AM
I vote for a bad, or going bad, voltage reg.
07-23-2011 08:29 AM
Tractor does it
I have a bosch alternator on my Case 580, I installed new brushes,very easy, but sometimes the battery would be dead. The diesel only uses a fuel solenoid so it will run a long time on a good battery if the lights are off. Sometimes i would get a charge the sometimes nothing, I took the alt into a repair shop and sometimes it charged and sometimes it didn't during the 2 minute test. The tech said there was a loose connection inside . $ 300 for a new alt. I just carry jumper cables and can go several days with no problem. I have a GM one wire to install as soon as I get Time.