I was going to say alternator (more specifically, the voltage regulator in the alternator).
I went through about four alternators in a three year period in my 110 (300 Tdi) before I got the one that is in there now (going on two years with this one).
When it was bad, the dash lights (well, all the lights) went dim to bright as it was under charging and over-charging. This was when I started carrying a fire extinguisher in my right hand while driving...
There is not much else I can think of that would cause the lights to change like that...
Try a volt meter on the battery while idiling in the drive. You should have 14.5 volts while the engine is running; no more (AND IT SHOULD BE ROCK-SOLID). With the engine off, there should be 11.5-12.5 volts (no less than 11.5). If the voltage does not check out, you may have a shorted plate in the battery as another thing to check. Swap in another battery and repeat the test and see if you have the same problems. Also, check the battery immediately after driving, and again after it sits all night. The voltage should not have dropped. If so, the battery needs to be replaced anyway.
Honestly, it still sounds to me to be the voltage regulator...
Owner: James Leach Global Expedition Services.
1995 110 Regular