Installing Low Fuel Warning Light in 242

[hrforever]

In the past I've been troubled by the inaccuracy of the original fuel gauge in my 242 and so now with the R Sport gauge I've been doing some homework to check the accuracy of this fuel gauge.

I've pumped the tank till empty, and got a reading of 281 ohms, at which point the gauge showed no movement from its 'power off' resting place. With 10 litres of fuel added the reading was 202 ohms and the gauge needle rests just above the Empty line. With another 10 litres added the reading was 182 ohms and the needle showed just over 1/4.

My research on this and other forums suggests the sender units readings fall within the parameters of what's acceptable, but I am concerned that with a gauge that shows empty, I still have 10 litres left (fair safety margin I suppose). So, I was wondering whether anyone knows of, or has installed a low level fuel warning light that can be set to activate at a certain ohms level and maybe is adjustable.

I have two other cars I drive regularly that have this feature and find it invaluable, but can it/ has it been done for older cars?