Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Fuel gauge sender/rack

Yes, both senders use the same wire gauge!

The resistance increases by 0.265 ohms per mm of float drop.

With a double loop configuration this means the resistivity of hte wire is
0.133 ohms per mm

This is
copper awg 26
or more likely
aluminium awg 24


I agree that the length of the sender is not optimal for the size of the tank.
However it is a red herring as far as improving the accuracy of the gauge.

As a brief recap:
As the float moves down the sender, the resistance of the sender increases and consequentialy the fuel gauge reading falls.

At some position (around half full) the resistance is sufficient to show empty reglardless of whether there is any more wire track left in the sender.

This position of showing empty must be the same for both senders as they both use the same wire gauge.

Fitting the longer sender is like replacing your 25 hour digital clock with a 26 hour digital clock and expecting it to be better at telling the time.

In order for the extra length of the longer sender to be usable, one must first solve the underlying calibration problems.

I did this, but then found other problems with the electronics of the car which were contributing to the fuel gauge's erratic behaviour.

It has taken a long time testing, programming and re-testing(with many further red herrings), but i am looking forward to finally having a working solution fitted to my car ready for grindelwald.

The optimal solution will be a 280mm sender with the other associated problems ironed out. However a 280mm sender by itself has absolutely no effect at all.

I do know that my old 250 mm gauge would show 0% with 5 gallons remaining in the tank and my new 280 mm gauge will show 0% with 2 gallons remaining in the tank.

Dolph

Assuming your maths is correct - ie the short one is 72 Ohms, with the long one at 75 ohm, if you put a 1k8 resistor across the long sender then it should give you 72 ohms at the bottom - not 75. If this is the problem then the longer sender will give 72 ohms at the bottom of its longer travel the same as the shorter one.

Man Alive!

I'm very interested where the upper and lower display resistance values were obtained. Was it by testing your own cars system or from a manufacturers data sheet?