cause of all lights going dim ?

[Hank70SS]

Well you can look in the factory assembly manual Bill, U63 Radio-Ground Straps. Two with an AM radio and a 3rd one with an FM radio. What you call the 'small' cable coming off the negative battery cable is 10g, same size as the pigtail coming off the positive battery cable. So if the positive pigtail can supply all the power needed the negative can supply the ground for that power. GM figured that was enough to carry the load for all lights and accessories. The starter is a different story and why the main cables go directly to the starter and engine.

I can show you 10 cars without those braided cables for everyone that has them. Those braided cables were never meant to be current carrying. Their electrical theory was a little messed up but they felt the braided cables would help suppress the electrical interference from the ignition. If they were meant to carry current one regular insulated wire would have been sufficient.

Like I said, if adding those grounds solves a problem then you have a problem with the chassis ground elsewhere.