Fuel gauge

[FLIGHT]

Hi
had to free up the float rheostat recently, after fitting a more modern spedometer/gauge to my 1956 moggy
I was surprised to see that full earth return is apparent when the float is fully extended down--i.e.--in an empty tank, which in turn causes the fuel gauge to read full tank !
Having rebuilt the panel completely i am reluctant to remove the speedo/fuel gauge to see if reversing the connections on the gauge make it read correctly,however, i cant in theory see how this would correct the situation, although i might be mistaken.
I would have thought all would be correct had the float increasedthe earth return in sympathy with the increasing amount of fuel in the tank---but i stand to be corrected !
Can anyone provide any helpfull information ?
Regards -- Flight

[bmcecosse]

I suspect the sender is just not compatible with the new gauge.

[FLIGHT]

Thanks for the reply---i presume the fuel sender on the type post 1963 is different to the earlier type in that it might be reversed in operation i.e.--earth feed increases to the fuel guage as more fuel is added--can anyone confirm this ?
rgds -- flight

[bmcecosse]

The later sender is certainly designed to work with a 'hot wire' gauge - so polarity doesn't matter. the early gauge I think IS polarity sensitive - since it simply reacts to current flow. Try swapping the connections on the gauge.

[FLIGHT]

Hi ! Thanks for your reply -- thinking it through, the fuel gauge is working as it should--responding to a full earth to give a full tank reading--but in desperation i suppose i should try a reverse connection which theoreticaly would push the guage hard over to empty---however--i have struggled to replace the whole instrument and glove boxes-----so the whole lot would have to be removed---!!--trying to avoid that but---may have no choice !
Appreciate your contribution, bmcecosse, --thank you !---Flight

[mike.perry]

Later fuel gauges work through a voltage stabilizer giving a 10V output. Earlier gauges were 12V, no stabilizer