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What is this under the tank R90/6
Posted: Sat Aug 30, 2025 9:10 pm
by focusrsh
Quick (and probably dumb) question . What is this black box with a red top under the tank of a 1974 R90/6.
Looks like something electric, but I don' want to start prying/pulling to take a look.
Re: What is this under the tank R90/6
Posted: Sat Aug 30, 2025 9:50 pm
by gsm_r100rt
Voltage Regulator. BMW Part # 12 32 1 244 409
Re: What is this under the tank R90/6
Posted: Sun Aug 31, 2025 4:00 am
by Rob Frankham
Yes, absolutely the voltage regulator... not the original but a BMW replacement part. The original would have been a metal can about 3 times as high as this unit and would be a mechanical regulator. This one is electronic and a little more efficient. The voltage regulator controls the output from the alternator and the charging of the battery by preventing line voltage from exceeding 14 volts when the engine is running. If you are experiencing charging problems with your bike, this might be the culprit although there are a number of other possible causes.
Rob
Re: What is this under the tank R90/6
Posted: Sun Aug 31, 2025 5:51 pm
by focusrsh
Thank you. I won't mess with it