A different problem, most probably a dash wiring malfunction:
Variant: 1990 4x4 FFR.
Problem/symptom: the three clocks to the right of the Speedo clock/odometer combo (i.e., fuel gauge, engine coolant temp, battery voltage) worked for a second or two when starting the engine... but then:
1. all three clocks' needles fell to the left as the gauges stopped working - they just lost power, they died, they kicked the bucket and started 'pining for the fjords'..
2. the square red "low oil" warning light comes on in the colourful array of idiot lights under the gauges (the lights you can minimise with the little tin lid). It looked exactly like the handbrake light. When I noticed it as I was driving I thought this was a broken fanbelt.
3. a square orange warning light comes on with the symbol of a carby butterfly throttle (i think its that). Because the headlights and wipers were on this is warning array is looking like a lovely Xmas Tree collection. In the Defender handbook this orange warning light is logically "number 18" but has no function or meaning apparently. But its orange and at least I know that bulb works.
4. i checked the oil on the dipstick: its on the lower dot...
5. The next morning drained the oil, changed filter, added the fresh oil and then restarted the engine.
6. The red "low oil" warning light did not reappear. Its off. The mystery orange warning light did not re-appear. Its off. All the gauges worked correctly and stayed working. No more problems. An oil change fixed the electrics LOL.
I think I have a dash wiring fault. The wire that powers the "low oil" warning bulb is probably touching/powering the mystery orange bulb as well.