My gas gauge is remaining at full. I have swapped out good sending unit no change. Jumped sending unit plug sockets 3-1 and 3-2, one turns on reserve light, the other makes gas gauge move to full. The gauge shuts off with car off and jumps to full when on. Not sure what else to check?

If the gauge always reads fully I'd focus on a bad ground either at the gauge, instrument cluster or at the tank. Grounds will be brown wires. Always full is an open ground, always empty is shorted to ground. This is from US vehicle experience but I believe it is the same for MBZ.

What happens if the sender is plugged in and the float is raised/lowered?

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Where is tank ground? I know sending unit works, traded it out of another car with working gauge. Also took out original sending unit and it works in another car

Sorry IDK where the grounds are located. I think the one behind the cluster will be easy to find though after removing the cluster. Also remove, clean and reassemble the grounds (brown wires) near and at the battery just for good maintenance practice.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Having two known good sending units is a big win. Now it is known that the issue is forward of the tank in the wiring or instrument cluster.

__________________
"Rudeness is a weak man's imitation of strength" - Eric Hoffer

When shortin pin 3-2 and pin 3-1 , the gauze reserve light comes on and needle moves from empty to full. Cleaned grounds in back of vluster

Maybe this will help a bit :

Attached Files

	1.pdf (66.2 KB, 15 views)
	2.pdf (53.7 KB, 16 views)
	1-2 ground points.pdf (262.0 KB, 14 views)
	3ground points.pdf (127.8 KB, 13 views)

Where are 3-2 and 3-1 pins located?

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

On plug that goes to fu sender at tank

If the gauge works by jumping pins at the tank and the sending unit is known to be good the problem may be the connection/connector at the sending unit. Clean and tighten the connections at the sender they may be loose internally.

__________________
"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Ok I’ll look at it again