SI Board draining batter

[steelynorm]

took my car to local independent.
they believe that my drain is coming from my SI board.
Does this sound reasonable..

[jeffnhiscars]

I can't think of what's in the SI board that pulls power

[AndrewBird]

The SI board is a common power draw. There are batteries on it that go bad and can cause an excessive drain.

[jeffnhiscars]

How does a dead battery drain power ?

[Jean]

Look at the etm for your car, and see if the cluster / is board gets constant power even when ignition is off .

If it does , then it's possible , and you can then check it by seeing what fuse is in line with cluster ..

[steelynorm]

etm?

What's an ETM?
Fuse 21 has been pulled and has the excessive amp draw.
Tachometer dome lights etc

Jean i noticed u were local,
Which shops do u trust locally?

[Gregs///M]

Yes, the SI board will cause a current draw. The dead batteries will switch all the transistors on and off very rapidly, which will cause excess draw. Think of of flicking your head lights on and off, eventually they will drain the battery.

Also the SI board can power the oil inspection and inspection lights even when the car is off.

Keep in mind replacing the batteries on the SI board rarely fixes this problem, there are about 4 capacitors, and 20 transistors and voltage regulators that must also be replaced. Feel free to contact us if you want it refurbished, we specialize in refurbishing the SI board for all vintage BMW.

[Stanley Rockafella]

My tach and mpg meter died. I replaced my SI board with one that was rebuilt unit(new batteries). Now tach and mpg guage are back to normal.

Seriously considering replacing the batteries on the faulty board to have as a backup/sell as rebuilt. The original batteries were dated 1988. New ones are from 2006 so hopefully I shouldn't have problems for another 20 years of so :D