Thread: Fuel gauge (S3) - how does it work?

The tank sender is a variable resistor to earth - I can't remember which it goes, full maximum or full minimum (changed in 1967)! The gauge is a thermal/bimetal strip type connected between the sender and a stabilised voltage supply. This voltage supply is from a separate stabiliser, a small box on the back of the speedo, that gives an average of 10v using a bimetal strip and a set of contacts that switches it off and on at an off/on ratio that gives the average voltage, and a period of a few seconds (makes life interesting trying to trouble shoot with a meter). The same stabiliser supplies power to the temperature gauge, which is similar. The slow response of the gauge means that the variation in voltage is not seen on the gauge.

Hope this helps
John

the sender is a variable resistor. it'll work in any orientation but the float actions going to be screwy. The connections and seals are also not intrinsically safe nor gas proof using them on LPG would retain the potential to be "interesting".

The original gauges work in any orientation and the wiring sequence goes

+12v supply - voltage regulator - gauge - sender- earth.

Found out the gas tank sender on the lpg tank is a 2 - 176 ohm sender which apparently is standard for falcon gas systems (designed to mate up to the original fuel gauge when the gas is on) so I'm not sure if this will work by the same principle on the land rover gauge or whether the ohms are wrong. Is there any tech data to say what ohms range the gauge needs or does it work purely on variable voltage?

the gauge measures current, the sender just varies the resistance to alter the current.

The current that goes through a thermal gauge will fry a modern LPG sender. Their resistance element consists of tiny surface-mount resistors and will only reliably drive electronic gauges. Just get a matching sender and LPG gauge.

Originally Posted by bee utey

The current that goes through a thermal gauge will fry a modern LPG sender. Their resistance element consists of tiny surface-mount resistors and will only reliably drive electronic gauges. Just get a matching sender and LPG gauge.

Can you get analogue lpg gauges? I want to try and keep the dash looking unmolested, at least from a modern point of view ie no led gauges. Or run with no gauge and just go from the trip meter. The sender is supposed to talk to a falcon ea-au fuel gauge so presumably using the internals from one of these should work?

you can make one...

use the resistance of the LPG sender to drive a PWM 12v power supply and calibrate that to run the fuel gauge.