New tank install - My tanks empty but the LED shows there is gas in the tank.
If your GAS IT tank is new and has not been filled up fully yet with gas but your LED display unit in the vehicle is showing some or all the lights then the likelihood is its nothing more than the sender unit when fitted on the tank under the vehicle itself (which works on a magnetic connection basis with the valve in the tank) has not lined up with the magnet on the actual float valve in the tank yet and the sender showing full for example is telling the LED display where is currently is - and thus giving a fault indication of the gas level.
The fix for this is easy - You don't need to do anything as it will fix itself when you fill up with gas and the magnet inside the tank lines up with the magnet on the tank sender.
The reason this happens is because when the tank sender unit ( that looks like a Percentage clock on the tank ) was fitted and left in a random gas level position during its manufacture and testing procedure, and if this was left at say 50% on the tank sender gauge then the equivalent LEDs on the in cab display will light up on the LED display and give you the impression it's got gas in when you know it hasn't. It will continue to show that false content until the 2 magnets on the tank valve and tank sender unit line up ( or pass each other ) which will happen when you fill up - as both magnets pass each other and pick attract to connect together. There after the gauge will work ok.
To confirm this is simple - The first check you can do if you have lights showing on your LED display is to do a visual check on the sender unit in the tank to see where that is at and what gas level it is sending the LED display - as it is this that sender the signal to the led in the vehicle. Its also worth checking the sender unit has been installed correctly - the 2 wires must be coming out upwards - as a clock hands are at 12 noon ( pointing fully upwards ) If you check the attached document ( which was created for testing the wiring ) but it will show you where the orientation of the sender unit you have fitted in the tank and which way up it should be and what it should look like
If you want to check your wiring then you can always take the gauge off the tank valve, in the reverse of when you fitted it , by removing the 2 very small Phillips screws that hold it to the brass tank valve that you installed, get a magnet on the back of the electric gauge and move the hands round to the empty position - as you tank is empty, and put them back together.
If your not sure if the problem lies elsewhere with the wiring then we have a section on this GAS IT knowledgebase covering how to check the install of the LED display and sender unit.
One other quick thing to note is if the LED is showing all green ( as in full ) then it could also be there's a break in the cable between the tank sender unit and LED unit or there's an earth fault. See this article here : https://www.gasit.co.uk/support/knowledgebase.php?article=85