Guages or brain box?

[6670charger]

Developed a problem with my gauges recently after removing them to change a light bulb, and not sure if this is a main computer or gauge problem. The car is a '93 518i/manual. After re-installing the gauge cluster, I find that the gauges all go wild when I turn the lights on. I hear a low humming sound, the tach needle goes psychotic, the other gauges flatline and the digital display at the bottom dims to nothing. The go back to normal when I turn the lights off, save for the speedometer which requires that I shut off and re-start the car. The odd thing is that if I drive the car for a while and then turn the lights on, everything is fine.

Everything behind the dash is plugged in correctly and firmly. My assumption right now is that this is some sort issue in the cluster. The light bulb I installed still doesn't work, although it was a used one so it could be bad. Could that be causing some sort of continuity problem in the gauges? I'll check that out tonight as I'm getting to the point where I've nearly reached NASCAR pit crew proficiency with removing/re-installing the steering wheel/air bag and gauge cluster.

[6670charger]

Turned out to be the large center light bulb in the dash. Must have had a short in it. Changed it during lunch today and now everything seems to work fine.