<E30>OBC Range indicator fixed

[Michiel van Wessem <jmvw@xxxxxxxxx>]

Hello,

A little while ago I was wondering why my OBC completely seemed to ignore
the fuel tank level and hence couldn't compute range. On the E30 Network
message board (see <http://www.bmwe30.net/> ), Chris Kuegler wrote the
following reply:

>(...) for adjusting the OBC, I have developed the following method: 
>Remove the cap at the front of your OBC. The cap is at the lower left of
the front panel. 
>Lift the fuel sender in the tank up, until the light in the fuel gauge
goes on. If you have found exactly this point, adjust the OBC between 5.0
and 6.0 L. 
>Thats it. 
>BTW: the fuel sender should read out approx. 70 Ohm full and 4 Ohm empty.

I tried it and to my surprise, it worked! I'm stubborn, so instead of
lifting the fuel tank sender, I drained the tank into a clean bucket by
shorting the fuel pump relay. As soon as I touched the adjusting pot on the
OBC, it jumped to 5.0 l. The contact must have become dirty. 

When I put the fuel back in the tank, the OBC registered it! I went to a
gas station and I filled up the tank. It indicated 47 l.

I think that for precision, the OBC uses both the signal from the fuel tank
sender and the fuel rate from the Motronics unit to calculate the amount of
fuel left. When the signal from the fuel tank sender doesn't make sense, it
discards it.

Thanks, Chris!

Michiel ('87 325es <http://www.vramp.net/~jmvw/cars/BMW/> )

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