Some great information above. I need to subscribe to the thread!
Regarding grounds for 1984: The engine electronics are grounded to the passenger side cam cover. That wasn't mentioned yet.
Regarding Warning Light flash. This happened to me today. I don't know why yet. I got an occasional downward blip of Amp gauge. Also, an ocassional few flashes of warning lights. Happened with significant throttle / load. Am wondering if its an intermittent alternator failure or a failing brake fluid level sensor. Don't know. Still running strong. Coincidence with your customer's issue.
On 84 thru 86 the warning lights are triggered by loss of alternator as battery power fades. They will all flash repeatedly until battery finally depletes and car dies. Its a wiring change that was made after 83. I've had an intermittent failing alternator cause this. Slight hammer tap would settle the alternator, but it would repeat after a week or so. Replacing alternator with factory rebuilt Bosch which completely solved situation on 86. But this situation today with my 84 seemed different. Battery was still very strong, got the amp meter blip, then a couple flashes, then recovery. Sorry, no definitive answer. Might also be some sort of short, as this 84 electrical system has suffered abuse.
Had some other various pictures to reinforce other posts:
Here's an 84 fuse panel.
See the site mentioned for ref.
Here's the back of it. Melted wires can happen.
These are the hot leads on the 84 panel, they aren't under a clear cover (minor difference from notes above)
I always replace all these, plus clean the heck out of them. Like Stan says, they corrode because of moisture from above.
