full fuel tank shows half empty on gauge

filled tank of series 2a 109 and found it shows only half full on gauge.

if unplug sender unit wire it goes full tank off the gauge.

took top off sender and there a wound wire and slider prongs and all seems ok but goes from 0 empty to 100ohms full.

is there another sender unit that goes 0 to 200 or more.

dash gauge is older one without voltage reg on back.

or can i mod the sender adding resistors to it?

Sometimes you just have to bend the sender so it sits at the right point.

Already tried that and ended up taking complete sender unit out but still only got 0 to 100 ohms on full sweep.

Need sender with more total overall resistance But Iis there one?

Surely if it is just the resistance that is causing the problem you could just put a resistor is series with the circuit so you get a higher reading but then wouldn't that effect the zero reading? I still need to connect mine on my land rover (fix it)

Im not sure if one exists with a higher resistance as one of my friends had the same problem and he looked everywhere for one.... maybe one exists. Although he got around it by adding more earths to the sender unit.

did read somewhere about adding a resistor but yes that would cock up the zero - empty reading so win one end lose the other.

have tried extra earth to lots places and a long one to battery but no change.

hoped there would be other sender unit ..................

next step i think is strip and rewind internal unit to get more linear resistane .

if no good ill be after a replacement sender....

Check your grounds. If you move sender manual how does the gauge read?

with sender out the tank and using full movemet of float travel means gauge goes from empty to half a tank.

grounds checked and double checked with multimeter to ensure no resistance found ie good earth.

will get some resistors and try find what gives a full tank on the gauge and see.

i think youd need a new sender ,greater resistance will only make guage read lower

jamesmartin said:

i think youd need a new sender ,greater resistance will only make guage read lower

Click to expand...

wot he sed ^^^^^^^^^

fsd normally equals 12volts.

thought about new sender but could not find one when i looked to replace this.

if anyones used a new plastic topped one then please send a link or poibt the way.

cannot go through pain of bleeding perkins fuel system when run dry...

will this not fit
https://www.google.co.uk/url?sa=t&r...y4HwCw&usg=AFQjCNFrifeEq4Oc3rwYQMHOEOWZ_KfepA

Looks ok from bolt pattern

Need checl what resistance gauage wants to see then call see if the sender falls in that range.

Be weekend before get to it as have filler neck to swap and gearbox oil to check

Post back finding later

Are you sure you're figuring this right? I'm pretty sure my guage reads (over)full when shorted to earth and empty when disconnected.

I had in the past managed to rig up a non-standard (ford) head unit to a wrong sender (Land Rover) as I couldn't find a proper one for my bus. With some simultaneous equations and a bit of head scratching I worked out how to mod it with 2 resistors to give pretty much perfect full and empty readings.

D