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Message: <blockquote data-quote="Don C" data-source="post: 401327" data-attributes="member: 762">Whenever you activate one bulb and another one in a different circuit comes on the culprit is usually a bad ground and the activated bulb is seeking a ground through the other bulb.Grounds (actually lack of) are the most common reason for multiple electrical issues in these 50-year olds. Make sure the battery ground cable is run correctly from the battery to bottom screw on the voltage regulator (this provides the chassis ground) and then on to a bolt on the engine block and that all connections are to clean bare metal. Using internal star lock washers between the connector and the grounding panel really help. I would also run another ground wire from the back of the engine block to the firewall to help with grounds through old, rusted connections between the various body panels. I have positive and negative test leads that are about 25 feet long 16-gauge wire that have a large alligator clip on one end that can clamp onto the battery terminals and the other end are normal sized alligator clips. This makes it easy to run a temporary ground to a bulb that has been infected with a gremlin. If the bulb then works properly, I know it's a ground issue. I can also run a temporary hot lead to a problem bulb, and if that lights up the bulb, I know that it's a positive voltage supply problem. I also have an insulated probe that can pierce wire insulation or make contact with connectors through the back of the bulb socket. If I do use it to pierce the wire insulation, I put a dot of liquid tape over the hole to keep moisture out of the wire.Digital volt meters don't always tell the whole story, because they don't place a load on circuits and can show battery voltage, but when there is a high resistance connection in the circuit the resultant voltage is reduced when a load is placed on it.</blockquote>

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