The battery is grounded to the engine, the engine should have two ground straps one on each side going from lower rear valve cover to the firewall.
The body has one ground strap going from the center right body to subframe mount area to the subframe.
I can't remember if there is a strap on the drivers side.
The dimmer switch can get corroded inside too, on the contacts.
On our farm some of the pickups get wet in that area when an irrigator get's in and out with muddy wet boots etc.
And moisture can accelerate the corrosion of the dimmer switch.
I have also seen the terminals melt where they plug into the dimmer switch. The corrosion causes the connector to heat up.
We are now having major problems with the headlight switches on later 80's pickups. They get dust inside on the contacts, heat up and melt.
You can see smoke coming out of the switch! Not good.
The new switches have most of the metal taken out of them and the function is no longer a sliding type switch but more like points on a distributor. The problem is that type switch while less prone to wear problems, is much more susceptable to dust fouling.
A couple of specs of dust can prevent contact.
Add that the contacts are covered in grease, (headlight switch) to prevent oxidation, and you have a head start on a fire!
The tail light sockets melt on the push in bulb type too.
Check my web page for First Gen Camaro suspension info:
David's Motorsports page
First Gen Suspension Page
67 RS 327
69 Camaro Vintage Racer
65 Lola T-70 Chev 350
Can Am Vintage Racer
[This message has been edited by davidpozzi (edited 05-09-2001).]