Dave;

You have muliple issues...so let's slow down here and not lump every instrument light and indicator lamp into one circuit. Instrument lighting is supplied by Fuse 11 and is dimmed by the dimmer [Refer to: http://www.sw-em.com/1800E%20Wiring%20Diagram.jpg ]...and this has ZERO to do with the voltage stabiliser (which supplies the temp and fuel gauges ONLY).

Indicators on the other hand are powered by the individual loads, and seperate circuits they are monitoring.

Aside from the dimmed inst. lighting circuit lamps (where the rheostat decreases the voltage supplied), assure your lamps are getting the full voltage by checking connections and for good contact at the lamp sockets.

A two volt drop between FB and inst. lighting circuit, while dimmer control is at zero ohms means you are loosing it elswhere...use voltmeter to locate...once you locate, you'll likely have a good idea as to the remedy.

Bulbs can indeed dim after many hours of use, when the filament is cooked off and plates onto the glass. Inpect lamps for mirrorlike deposits on the inside of glass envelope...if this is present lamp needs to be replaced...light doesn't penetrate this layer.

Good Hunting!