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Old 09-12-2019, 07:08 AM   #26
Kevin in NJ
Senior Member
 
Join Date: May 2010
Location: South East NJ
Posts: 3,398
Default Re: Stupid Question #2: how does an iron frame act as a ground on our cars

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Current is carried on the outer edge of the material. That is why larger power lines are hollow to reduce weight. In the end it is just surface area. This is something you get to do the math when you get physics or engineering courses.

With the A it is not the iron that is a problem. It is in understanding the ground paths as they are complicated. When we restore the car we do a lot to cover what would be the ground paths.

So from the engine to the frame you travel from the driveline up through the springs (spring bolts to be exact) to the frame as one major path. You also have the often not installed engine shields. Of course you have to be sure that the various bolts have bit though the paint to make a path.

So in restoring my car. I tinned the area where the pos strap attached to the frame and then put tape on the area so no paint is put there. I made grounding contact paths from the frame through the fender brackets into the headlamp bar and put tape in the sockets for the headlamps before paint.

If you used a thicker paint on some areas then you need to be extra certain the lock washers cut through or maybe cut through the paint first. A little extra care goes a long way to a more reliable car.
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