When I put on my brakes with the truck in drive the alternater drops from 14 to 12 do you know what the problem is
My car has an automatic transmission.
This may be a result of the decrease in engine RPM which results in the alternator producing slightly less than the normal output of 13.8 to 14.2. When stepping on the brakes, this also produces a slight drain on the system due to the brake lights being activated. If the engine dies when pressing on the brakes, this may be a different issue altogether. I would suggest having an expert from YourMechanic come to your location to diagnose your charging system.
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