What's going on here???! Problem started last weekend and maybe a result of my checking ignition trouble codes and then leaving ignition on for 4 +/- hours. Car started right up but here's what happened:

Turn key to ignition and only 2 dash lights come on: overdrive arrow is bright and, if parking brake set, parking brake bulb is barely visible red glow. The overdrive button on shift lever switches arrow off/on and lowering parking brake lever shuts off faint glow.

Turn key to start: engine starts and runs just fine. Clock runs, but fuel/ temperature guages don't move and with car in gear and moving, speedometer doesn't budge. If engine runs for awhile without guages working, alternator light will come on.

Turn headlight switch on and off a few times with ignition on: overdrive arrow does not light and other ignition bulbs light up same as ever. If you do it while engine is running, engine stumbles a split second and then runs just fine and guages start working. If you do it while car is driven guages and speedo suddenly work.

Car has 215K and only other electrical problem was blipping speedo needle that was mostly cured by replacing capacitors on speedo circuit board. Had to drive car 700 miles since Sunday to wife's family reunion and expected smoke to come out from under the dash and then problem would be obvious but it never happened. Battery never ran down but am wearing out headlight switch getting dash lights working. Last time must have have turned them on/off 20 times. Rarely, you can insert key turn in ignition and dash lights burn but mostly have to work headlight switch vigorously to get them to come on.

Swapped alternator voltage regulator Sat night but no change. Then thought it was ignition switch problem with its terminal 15 but that also feeds main fuel pump relay and if terminal 15 was bad car should not start. Also thought switching head lights on/off caused terminal(s?) or electrical connection to arc closed so dash worked but why does motor stumble when lights switched on and off with motor running. Also wondering if there's bad diode(s) on dash cluster circuit board but why would that cause motor stumble.

Have 89 Wiring Diagram Green Book but hope someone has solved this one before.

Steve L in Charlotte, NC 84 240 w/350+k (waiting for parts), and this 89