The stock sender is 70ohm empty - 400ohm full and I can't find anything that fits that range. There's an adjustable autometer gauge but it says its range only adjusts up to 280ohm. Has anyone found anything?
I just realized there are two senders, one for each side of the tank and their values are averaged. If I were to connect them in parallel, this would put its resistance right in range; however, since the left side of the tank empties first, this won't work properly. At half tank, left side resistance will be 70ohm and right side 400 - which means a total resistance of about 60ohm - but a true half-tank resistance needs to be ~118ohm(235/2) to read properly. Series would be the correct way to wire them to get a true average, but obviously a 140-800ohm gauge isn't going to exist if I can't even find a 400ohm gauge. I'm probably going to have to build some type of averaging circuit for this anyways.
OK I think I may have come up with a solution. Run the two senders in series with a resistor in parallel. If I use a 300ohm resistor, this will net me a total resistance of ~95ohm empty and ~218ohm full. Any resistor will work as long as the total full-tank resistance is less than autometer's 280ohm limit, I choose a higher value resistor to get the most resolution. Guess I just needed to write this all down and let the ideas bounce around inside my head. Maybe this will help some other people looking to do the same.
Update for anyone that comes across this thread:
I have my gauge wired up like I said - it works, sort of. The first half tank only brings the gauge down to 3/4, the last half goes down to 0. Haven't decided if I'm going to mess with it any more.
I was looking at this unit when chasing problems on my gauge. Think I fixed mine but if it end up still being a problem, i'll be buying one. I confirmed with the manufacturer that it will work with BMW sender values.
http://www.aircraftspruce.com/catalo...iABEgKupvD_BwE
S.F.
A dual tank gauge is definitely a good idea, but I have 5 matching gauges in my dash behind the stock glass, this would look very out of place for me.
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