The Stovebolt Site Forums The Shop Area The Electrical Bay Ground question

This question arose at the A & W Thurs evening. A nicely restored '41 Chev pickup cruised by. Its tail and brake lites were clearly malfunctioning. We mentioned it to the driver who responded that the work had been done by a high-end restoration shop and he can't imagine what the problem could be. Underneath are fresh wood cargo box mounts that suggest that the problem (which the owner seems reluctant to acknowledge) is that the lites are not grounded (are wired to the box which is isolated)

What is the correct setup? Wire individual lamps to the frame or run a strap from box to frame and if so, where does a strap normally get installed? If the latter, is a strap available from suppliers or would you just rig up a battery strap?

sandra

A good ground strap to the frame is never a bad idea. But,
originally from the factory the box would be grounded at
numerous points thru the fender to the running boards and
aprons via their bolts to the frame. The current draw is very
small for the single or dual tail/brake lights of the day so
it didn't require much of a path to complete the circuit.

If the restoration shop was SUPER careful when assembling the
truck it is possible, that it was kept insulated by the layers
of paint, primers, gaskets, fender welting from establishing
a good ground. Tightening the bolts SHOULD have cut into the
bare metal enough to establish a ground but it is also
possible that it didn't.
Bottom line is.....ground straps are a guarantee that
there is a complete ground return.
dg

Sandra,

An excellent question.

Many of my restored Suburban's lights behave as you describe (especially the three rear lamps). We stripped and painted all sheet metal. The epoxy primer and urethane finish-coat is probably resulting in very poor grounds.

I have excellent original ground straps (and a few additional ground straps) and they all have excellent/clean connection-points.

I have been neglectful in fixing this dangerous situation. The annual inspection/inspector lets me get by with the very dim and sometimes erratic rear lights/lamps.

I plan to use a small diameter metal-brush drill bit to clean out sheet metal screw holes. After I get bare metal, I'll use a conductive anti-oxidant grease to allow conductivity but prevent rust.

Some holes are not accessible to a drill. I'll probably run an unsightly ground lead to a screw on those lamps/lights.

I'll test the quality of grounds with a continuity tester.

I'll do the wire drill-bit/brush in screw holes before I install sheet metal on the two trucks we are restoring.

It has fender welting around both fenders and continuing to the running board ends

However it also has a rear bumper & the brackets are of course bolted directly to the frame, so perhaps those brackets would make a good ground(?)

If you want to check the quality of existing grounds to lamps. Use a long electrical lead between the battery ground and the lamp (connect the lead to lamp attachment screw, if it is accessible). See if the lamp becomes brighter (I'd do it at night).

Tail lites/mounting brackets are familiar style sold by Jim Carter (and others) for restorations of the 1941/46 era

What is "lamp attachment screw" please?

The attachment screw/post on a lamp/light - the ground would be made from the sheet metal (or frame) to that screw/post.