Can anyone point to which of the many pins on the 1988 S4’s instrument cluster’s four connectors are the ones to which power and ground should be fixed in order to test the illumination lamps circuitry without having to reinstall the cluster? Testing individual bulbs is not the goal at this point. They’re all fine and make good connection with the panel. But the LED replacement write-ups I’ve seen don’t indicate the panel polarities on pre-1989 MYs, and I need to see whether the new bulbs’ polarity as installed is correct for the circuitry in the panel.

Any suggestions are most appreciated.

I may have an answer, so I’ll post this in case it helps anyone else.

There’s a great write-up on this exact topic in a 944 forum I found, and the photos look at first glance like my 1988 S4:

rennlist.com/forums/924-931-944-951-968-...led-replacement.html

It addresses both circuit panel polarities and power and ground pins. If it works for me I’ll post an update to let others in my situation know.