I have a strange problem with my 1992 Daihatsu Applause Executive. Essentially, when I turn on my lights (and the dashlights come on) they flicker like crazy. The indicators flash, the lights dull in and out, and the tacho jumps around. The speed appears to be correct. When I turn the lights off, the tacho is fine, and the indicators come on correctly when I turn them on. The problem exists only on the dashlights. The outside indicators work correctly in any case, as do the headlights.
The really weird thing is, it only seems to happen when either I have higher revs (say, above 2500rpm) or the car is moving. However, the moving may just come back to the fact the revs are up.
I disconnected the dash lights, but left the headlights on and the problem with the tacho jumping around seemed to disappear, which suggests to me the problem must be specifically related to the dash light circuit.
Any suggestions on what it could be, and how I might fix it?