I am already changing the fuel sender unite to the gas tank 1989 300-E because it sticks and will not give an accurate fuel tank reading. I was told the orange warning reserve light that is suppose to show low reserve fuel in tank doesn't function, could be a bulb or related to the fuel sender unite I don't know? Do I need to pull the instrument cluster to check the gas gauge ? What steps to I follow to do this proceeder? can I check with a low amp DMM?

I went to check the forum and found the directions to pull the instrument cluster if need be. On 1989 W124 models if you turn the key to the on position to light the warning lights up is the fuel low warning reserve lite suppose to come on though I amagine it would and if not that would point to a bad bulb am I correct? Is this bulb accesssable with the instrument cluster once out or is it internally built into the gas gauge?

I thought of another important question. Should I disable air bag when extracting instrument cluster? How is this done , do I need to do this ? Very Very Important!!!!

This forum is great:
Bob Geco
family car 1989 300E 170,000 miles

Bob,

The fuel sending unit is a long tube with two resistance wires, and a float that connects them. When the float gets to the bottom, it connects two contacts that light the light the low fuel light. It is "easily" removed and cleaned, but be gentle on the wires so they don't break. The fact that you have both the light and gauge acting up at once talks to them being dirty.

Get the manual on your car for details on removal, but it is simply a large nut and electrical connector on top of the tank. Remove the tube slowly, as it will be dripping fuel for a long time. To disassemble and clean, there is a round nut on the bottom of the sender that comes off, then a cover and baffleplate and the tube will drop off. They will be gunked up. You'll see
the contacts and wires that need cleaning.

Does the bulb light when you turn the key for lights check? Have you ever actually run it down that far?

No, you don't need to pull airbags to pull instrument panels, should you need to. "All" modern Benz panels come out with two hooks reaching in beside them, turning, and pulling the panel out against the friction fit of its rubber "gasket." Put the steering wheel in the full "out" position for added clearance. You can buy them from the stealer or just use very stiff coat hangar wires with a 1/4" hook bent on the ends. Walk it out from side to side, as it may stick if it's been forever since it has moved out of there.

Gerry Visel
67 230
83 300TD
87 300SDL
92 400E

btw, the really quick bulb check is to turn the ignition key to position 1 and see which bulbs do/do not illuminate. The reserve indicator will also light if the bulb is okay.

If it lights up, the issue is not in cluster, but further down...to the tank!

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