Splochy Instrument Panel Lights

A couple nights ago I noticed that my instrument panels lights were not correctly lit. The number on the MPH gauge were ok but the 60-140 km/h were not illuminated. A middle portion of the needle was also out. The end of the need on RPM gauge was not lit either... among other splochiness of the lights.

Something similar like this happened five months ago when I took it to a dealership who said my alternator had an intermittent problem. So I had the component replaced. A difference between this time and last is that, last time, the gear light had also come on and my car ended up dying at a red light.

Thinking it’s the same problem (after hearing refurbished alts had a 20% failure rate) I started the car and disconnected the battery. It continued to run with the A/C, radio, and headlights on. However it idled erratically between 400 and 1000 rpms. When I revved the engine up to >1500 rpms, the check engine light flickered on and off. Next I had the free electrical alternator test performed at Advanced Auto Parts; they reported the alternator as being fine.

Any ideas on what the problem could be ? thanks for any help !!!

btw its 1993 318i

A] PLEASE DON"T DISCONNECT THE BATTERY with the engine running ! ! ! you lucjed out if the alternators diodes are still ok.........the alt. needs the load and polarity of the battery to function AND protect itself. unlike a generator, it needs B+ to perform. running one open circuit like you did can POP the diodes instantly.
B] the most common problem with the VALEO alt. that's probably on you car is the Voltage Regulator, I've rarely needed to replace the entire alt.
C] the dash lamp problem is probably just burnt out bulbs which require pulling the cluster to replace.

I agree, it seems that you need to unscrew the cluster and replace the bulb; not too expensive.