Sending unit Resistance

48Sed

Does anyone know what the Empty and Full resistance is for a 46-47  gas tank sending unit?

Geoff

Are these not a bi-metal unit?

bob ward

I don't know the values, (typically 50 to 100 ohm for most systems) but if your high resistance is too high you can fool it by using a resistor of the right value in parallel with the sender.

For a top read on how your fuel gauge system works (this is all Prince of Darkness stuff but the principles are the same) go to mgaguru.com

Park_W

These units (through 1950) are not a resistor type.  They use a bimettalic strip, one in the gauge and one in the sender.  They work together to display the fuel level, and are designed to be pretty immune to voltage fluctuations (within reasonable limits).  Fords used this same type gauge (and same provider, King-Seely) until the fifties, when they and Hudson changed to a resistor type unit in the tank.  Success with replacing the original type sender with a resistor type has been, shall we say, mixed.  In spite of the claims of some providers, it's pretty tricky to get accurate readings on the gauge, especially if you'd like to have reasonably accurate readings throughout the range.  Typically it requires many attempts to bend the float arm just right.  I'm in the middle of this process at the moment, on my '47, and am still playing with the float arm setting.

Geoff

Park, perhaps if you fitted a 5 volt regulator  you may have better results.   This seemed to be the major change in  '51, using a 90 ohm resistance unit in the tank.   The first fuel gauges used by Hudson used a double coil gauge and a 180 ohm tank unit, then in '34 they went to the  twin bi-metal system, both of which didn't matter what the input voltage was.  Then in '51, as you are most likely aware, they used the 5 volt regulator.

Park_W

Geoff, right now I'm fighting the battle of getting the gauge to read correctly with 1/4 tank of fuel, with the system supplied by a steady 7.2v. from an external power supply.  I'll worry later over stability of the reading with voltage fluctuations.  If it's nearly correct while being driven, I don't care about its reading a bit low at idle.  (The car has a '51 generator and regulator, so does provide steady voltage when driving)..

Park_W

Well, at last the job's finished.  Finally got the righ bend in the float arm, so it reads correctly at 1/4 tank and 3/4 tank, with engine at moderate driving speeds.