i was accelerating my '89 190e2.6 harder than usual on a very cold morning (after proper warmup of course), and suddenly i get this loud high-pitched sound from the instrument panel that sounded like a dentist's drill, so it freaks me out and i start to pull over, but the sound suddenly stops after about 5 seconds.

all instruments - tachometer, speedo, etc seemed fine and no warning lights had come up.

My ventilation fan makes a high-pitched sound also (needs lubrication) but it is quite different. So i guessed that the ventilation system went awry which somehow turned on the "fast defrost" for the windshield, so i turned off the fans altogether, but it was not the cause.

are there any electric motors behind the instrument cluster that can cause this?

can it be related to the speedometer/speedometer cable, and the subzero temperature? Could this have been caused by my sudden acceleration which could have caused moving components of the speedo cable to rub against other components?

it better not be the airbag ...