Test for bad alternator??


Buick = $$$
Jul 2, 2009
My alternator is a 140 amp and about a year old. Sometimes I notice the head lights at night dim back and forth so just curiouse to know how to check it? What should the voltage be when running?
one way to check it with the volt meter is check battery voltage make sure its fully charged 12.5v with car off now turn the car on and the volts should read higher high 13v to 14+ volts that means ur alternator is charging the system now if the 12.5 remains the same or a bit lower wen u turn on the car ur alternator is no good thats just a basic way to check i just did it last week mine turned out to b good another way is to just remove it and take it in to a auto parts and have them test hope that helps
when you say turn the car "on", do you mean turn key to last position before ignition start? I also just started having starting issues. I'll post that next.
sorry should of been clear when on i mean fire her up to see if alternator is charging hope that helps
Most good alternator, starter repair shops can check, usually at no cost.

These cars are known to have bad ground issues & you might be having ground issues.

Did you replace the inadequate #10 gauge wire alt to batt with a #4 gauge wire?