RCI fuel cell sending unit / equus gauge not reading right

[dazedand confused]

Bought an RCI 16 gal fuel cell with built in 0-90 ohms sending unit . Also bought an Equus after market gauge thats made for 0-90 ohms with 3 prongs - ground ,sending unite, 12 volt power . I installed the fuel cell like I was suppost to and followed the instructions on hooking up the Equus gauge . filled up fuel cell and the gauge read empty when full and full when empty ???? at first I thought it was a bad sending unit so I bought another 0-90 ohms fuel sending unit for the fuel cell and it still reads tge same ?? I also swapped the 2 wires around on the sending unit and still no change ???

 

[67Dart273]

Some gauge / sender units go the opposite direction so you must be sure they are compatible

Also some gauges are actually "3 wire". The 3rd wire is often the case which must be grounded. These are called a 'bridge' type circuit....Like this one. This is also an example of a circuit where "full" is most resistance instead of least

 

[dazedand confused]

yep the aftermarket gauge has 3 prongs on it

 

[67Dart273]

About all you can do is go back to the docs on the gauge, check them out carefully, and make certain the sender is compatible, at least for starters. Then make sure the sender housing is grounded if it needs to be, as well as the gauge shell