Gas gauge floats and will never tell accurate amount of petrol in the tank

Yes it sounds like you have found your own problem the float in your petrol tank is faulty and needs to be checked out. Check the wiring to the gauge is ok before doing anything at the end where the wires connect to it.

Your gas tank has a float inside that is kart if tne. Fuel. Pump assembly that indicates the amount of fuel in the tank..it sends a message to the gauge...sounds like the float is sticking when the gas is sloshing around when moving..causing a false read being sent to the gauge. Most times the tank has to be removed to replace..good luck..

the sender unit in the tank is defective .like the float is full of petrol or the ceramic resistance is broke

How far off is the gas gauge? If it is only 2 or 3 gallons off, this is a common occurrence.
Although annoying, there isn't much that can be done as far as adjusting it. It's set at the factory.

I'm not sure I am understanding your question. The low Fuel indicator light comes on, depending on how sensitive it is set, when you have between 2 and 5 gallons of gas left in the tank. This also depends on how accurate your fuel level sending unit is reading the fuel level in the tank. The low fuel level light depends on the level of fuel in the tank itself but other than using that sensor it has nothing to do with the fuel gauge itself. The fuel gauge may or may not be accurately showing the fuel level.

try the float it could be full of petrol

the float inside the sender unit is full of petrol and need renewing ,or take plastic float off and tie a cork to it

Mostly likely you have a tank mounted fuel gauge. If your vehicle is pointing down hill the guage goes up or down. It is usually the fuel level in the tank that makes the float go up to tell you how full the tank is, if fuel is sloshing around then level fluctuates. I would say that if it stabilizes on level ground and at a stop, and you can get a stable fuel reading then this is more of an annoyance than a problem. If you can get an accurate reading and you do not run out of fuel you may want to leave this one alone, you will have to drop the fuel tank and replace the fuel float on top of the gas tank which can be labor intensive as well as expensive.

If you mean that the gas gauge is floating and you do not know the amount of gas in the tank, then the most common cause for this is the fuel level sensor in the tank. The fule tank would need to be removed to replace it.- Tech jk

Bad ground on sending unit or bad sending unit. The sending unit is located in the gas tank and is inserted into the top of the tank. The tank needs to be removed from the car.