Turn signals don’t work when headlights are on

RedFish said

Grounds in general; Once the negative side of a circuit reaches the chassis, in this case core support, it still needs to reach the negative battery terminal. For many, a single factory jumper between firewall and engine then through engine block to neg' battery cable served forward lighting and everything else that is chassis grounded.
The most common mention of improved negative path is adding a jumper wire from instrument panel to dash.
Neg = neglected?

Click to expand...

A good way to improve battery--to--body ground is (V8) on the rear of the driver side head are the same holes that are on the front of the pass. side head. Use a short bolt and use an "eye to eye" starter cable about a foot long and bolt to the firewall or the master cylinder mounting stud

The great thing about Mopars is that once you DO get the battery solid to the body, then the body is pretty much welded. So if you get a good clean connection at the "other end" you have it.

(^^This statement may not apply for EFI etc with EMI sensitive circuits that is another matter)