I have a 2001 Monster S4.

The fuel level sensor hasn't worked since I bought the bike. This is mostly an inconvenience, but as there is no reserve facility it means I need to keep a close eye on my mileage or risk running out of fuel.

Recently I've had issues with the indicators not working while the bike is in motion. On testing when stationary all lights and switches seem functional, but later when riding the indicators failed to work. It was daytime so I'm not sure what else was/was not working. Testing later on the driveway the indicators did not work, but on turning it off and on again, they worked fine. I rode it again a few days later and the same thing happened.

Where should I start for troubleshooting this intermittent electrical fault?

Is replacing the fuel sensor something I can do at home or will I need workshop facilities? I have a fairly comprehensive set of hand tools, but limited power tools and no welding or other specialist tools.

  • (not really familiar with bikes) I would start with the connections at the battery and ground wire. Make sure the connections are clean and solid. Check any other connections with problem items. Might need to poke around with a test light to find the source of the fault.
    – rpmerf
    Apr 25, 2016 at 12:57

1 Answer 1


Seems to be an easy job. Check out panel #18 and parts list for panel #18. You are going to want to see if part #5, (PN: 592.1.010.1A) Low Fuel Sensor is available before you start the job. I found the parts manual here.

You are going to have to drain the tank completely first. Note: its not clear on if your sender is broken, has a cut wire or is simply not connected. If it were me, I'd talk to your parts guys, understand their return policy. Best deal is to ensure the part is in a sealed package, and then return it with seal NOT broken, if that works for them. If the part is cheap enough, just replace it. You should get a new gasket / seal as well as the sending unit. (PN: 789.1.001.1A)

It looks like only simple tools are necessary for this repair. I would guess an open end wrench for the sender, and whatever tools are required to remove the fuel tank from the bike.

Holy Cow Batman... I just did a quick search online to check out the price of that sending unit. Ouch. Big Ouch. (>$200) At that price I'd definitely remove the existing sender and see EXACTLY what's wrong with it, before ordering the replacement part. I'm pretty sure the sender is a float with a magnet in it and a hall effect sensor, but it could also be a variable resistor device with sliding fingers on the contacts. Sliding fingers on resistive elements definitely go bad with time. The float goes up and down inside a tube (unless its water logged or broken inside) If that's the case you must replace it.

Its also possible that you can use a volt ohm meter to verify the electrical functioning of the sender (given that you have a detailed service manual that provides the specifications.) I'm going to let you chase that one down.

Good luck with it, its a nice bike!

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