Originally Posted by
Panman
Hi all- I've seen a bunch of past posts but haven't found the fix yet. When full my gauge reads "full". When empty (I ran it out on purpose) it reads about 2/3. When I bought the car the sender was corroded so i replaced it with the slk320 equivalent, about 200 ohms empty, 5 ohms full. Checked wiring per the shop manual, continuity good, no shorts or opens. Instrument cluster provides about .7v at the unplugged sender connector. So I replaced the instrument cluster- exactly the same result. With the fuel gauge inop, car won't complete OBD2 monitor tests (cat & evap)- so car won't pass N.Y.S. inspection. All because of a fuel gauge! Anyone with first-hand experience? Love trhe car, but... Any help greatly appreciated! Thanks, the Panman
Sounds like you have done all the correct troubleshooting. So I'll detail what I have found and hope it will help: Mercedes part number for sending unit is 170 542 11 17 original, then came 170 542 13 17 and now replacement 170 542 15 17.
From the 2008 service manual empty should read 20 ohm and full is 270 ohm. Voltage measured at the tank/sensor connection is 0.7 volts, as you have found.
When checking shorts and grounds the connection at the instrument panel must also be disconnected. Skip a continuity test and check ohms directly to ground and to each wire as well as the two wires to one another.
It is a simple two wire connection, no splices, no other wires between the sensor and the alarm unit integral to the instrument cluster. It sounds like you have taken all the right steps. I know from experience when Mercedes replace an original part with a replacement part/number there is sometimes something missed in the process and the new replacement will not work like an original. M60A3driver gave good advice. I too have bent the arms on fuel tank level sending unites to make them work correctly. Good Luck!