How to chech erratic fuel gauge 90 van dura van.? Up and down behavior

Could be a faulty sending unit in the tank or the gauge on the dash.

fuel gauge sensor in the fuel tank is faulty.
replace that.

The fuel sender is in the tank and is part of the fuel pump module ( all in one). the fuel sender is a rheostat and is like a dimmer switch in you home to dim lights, the higher the level of fuel the more voltage the computer sees hence the lower the fuel the lower the voltage it sees. With the age of the car this is likely the problem. But there is a part in the instrument cluster that reads this voltage and sends power to the gauge intermittently. In older cars it was called a anti slosh module. It was there because as the car went up and down a bumpy road the gauge would read erratically. the cost can be prohibitive to fix this but if you can live with it i would. If not expect to spend 600 dollars or more to trace it down and fix it.

It sounds like a problem with the fuel gauge sender unit in the fuel tank which has worn out and gone open circuit and needs replacing. Access to the unit is usually through a removable plate in the floor in the rear of the vehicle. Disconnect the wiring connector and any hoses and then remove the securing screws. Replacement is done by reversing procedure.

Fuel sending unit is going bad on it. It is located on the fuel pump inside the fuel tank.

Definitely the gauge can be changed, provided the float in the fuel tank is OK, i.e. no leaks. This float connects to a potentiometer which records the current flowing thru it and displays it in the gauge. So before replacing the gauge measure the current and match that against the quantity of fuel in the tank...............sodeep

Probably easier to replace fuel tank sender unit as constant on off condition heard or not cant be good .Potential electrical spike.

The blower motor resistor can cause eratic behavior and the loss of some speeds and not others. I would check this first before replacing the motor.

I think the ford 350 might be a loose ground wire. This can cause the erraticness within the gauges.

The windstar is a faulty sensor switch on the brakes master cylinder. It leaks brake fluid into the wires that are connected to it causeing a short circuit and resulting in a blown fuse that powers the AC, cruise control, odometer, speedometer and the ABS light to remain on. This issue can also cause a fire. This fire can occur even when the car is off. To fix the problem go to this URL - http://www.fordwindstarrecall.info/

You don;t say whether the fuel gauge is reading accurately, or whether it's always on empty. If the gauge is always showing empty, it's most likely a problem with the sending unit in the fuel tank. Check the resistance across the two terminals of the sending unit.

On a C900, the fuel sender level unit is separate from the fuel pump and located on the right side top of the tank, accessible by removing the trunk floor lift up panel (the pump is located on the left side top of the tank.
Possible problems are: electrical line off or broken, float not working (it's fairly delicate); or gauge not working.

Test the resistance of the sending unit with the lines disconnected, the resistance should be 2.6 to 3.8 ohms full tank, 63.3 to 67.5 ohms empty tank; and test for voltage across the top of the sender unit, if no voltage, that's likely the problem!

If the gauge is otherwise reading accurately (showing 'full' for a full tank, etc) then the problem is likely a gauge malfunction and can be simply replaced.

Good luck!

Saabreur