[funkybird]

The tail lights, front parking lights and side marker lights have failed on my 73 Firebird. Headlights still OK so Im hoping the switch is OK. I thought I'd check the ground before I start tracing the circuits and ripping the loom apart, but the tail light wires seem to disappear back into the loom without grounding. Has anyone been here before and knows where is the ground point for this circuit?

["QUICK-SILVER"]

Headlight part of the switch is different than parking lights. One switch but two different sets of contacts and two different power supplies. So check for two hot wires going to the headlight switch first. Parking lights power is the tail light fuse.
If you've got parking light power going in to the headlight switch, check for power coming out with switch on. Check at switch, bulbs, or body connectors.

It's possible to have lost both front and rear grounds. Front parking lights usually share the same ground points as the headlights. That's what has me thinking lost power instead of lost ground.

Just in case, rear ground should be bolted down in the trunk before you get to the flat/ribbon wire body connector. I've seen them bolted to the trunk floor just in front of the tail light panel. So shouldn't be any need to un-wrap harness. Ground wire shoud be visible sticking out of harness.

[funkybird]

thanks buddy. Top diagnosis - the switch is faulty. I will order one up from our host. Removing it was weird. I had the whole dash in pieces before figuring the switch has a release clip with access from below... Doh!