I have a 85 gmc and I've tested the alternator
battery and starter. All are good. When I drive and
come to a stop light the interior lights and
headlights dim but when I speed back up all lights
are bright again. Any ideas where to start?
Some "flairing" of the lights in relationship to engine speed is normal on a non-computer controlled vehicle. If it's excessive there's a problem. Such as a bad alternator drive belt or serpentine belt tensioner, if equipped. HTH. -Jim
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