Disappearing Fuel Level

getting in the car could cause sloshing.

is the dash out of the car?
if so you can test all funstions of hte dash out of the car.

you will need some jumpers and a car battery

I dont have the particulars of which pin is which but you can figure that out with the Factory Wiring diagram.

you will need to connect batt negative to the metal housing and batt positive to the propper pin.

Now connect, per the wiring diagram, the proper pin on gauge for temp, or fuel and connect to resistors ( 5 watt should do ) connect the other end of the resistor to batt neg.

(this is just a ROUGH example PINS are NOT correct)



(The below links are for reference only I am not recommending these particular items)

This will simulate empty or engine cold (~75 ohms)
Resistors - 5W, Wirewound, Power, Resistance: 75 Ohm 603016355715 | eBay

this will simulate 1/2 tank or engine at normal operating temp (~22 ohms)
30pcs 5W 20 ohm 20R Resistance Ceramic Cement Power Resistor Kit Part 911346346632 | eBay

this will simulate full or overheated (~10 ohms)
10pcs 5W 10 Ohm 10Ω Ceramic Power Resistor Moisture Resistance | eBay


You could also get a variable resistor 0 to 100 range 1 amp or 5 watt capability should do. (don't go under 7 or so ohms or you might cook the gauges)

For lamps in the dash, use the same type of hookup but follow Factory wiring diagram for plus and minus.