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Discussion Starter · #1 ·
I have a '39 Pontiac with V.D.O. gauges....the fuel gage has been all over the place.....I just changed the sending unit (I checked the old one, and it was NOT steady at all upon taking ohm readings).
Bought a new (VDO) sending unit...checked it first, and it was "spot on" as far as reading 10 ohms empty & 180 ohms full, so I know the sending unit is good.
Installed the unit, and....as long as I'm going straight down the road, or even real mild turns, it reads fine...but when I make a fairly sharp turn, it wanders around for a bit, then settles back to about where it should be.
It almost acts like it "should" have baffles in the tank to keep the fuel from sloshing around.....maybe it does...for all I know!
Anyone have ANY ideas, they'd be greatly appreciated!!
 

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You are experiencing the result of what's called "free surface effect". As long as there are no baffles in that tank to keep the fuel from moving side to side the fuel gauge will do what you are seeing.

My 36 Chevy does the same thing.
 

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Occasionally, the addition of a 10uf 25-50 volt electrolytic capacitor across the sending wire and ground will help stabilize this. It provides a slight time delay to the sensing input by bleeding stored voltage back into the sensing input, stabilizing the circuit from sensing to quickly when fuel in the tank is sloshing due to acceleration, turns, braking or bumps.


A 10uf 25-50 volt electrolytic capacitor usually cost no more than a few cents each. If you can’t find one, send me a stamp and mail one back to you.
 

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Discussion Starter · #4 ·
THANX to all for your replies.....I will toss these around & try to decide what I wanna do...if anything!!
 
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