Fuel Gauge Issue

[RickyBobby]

It used to be that when my fuel lamp lit up on my 06 Dyna, I could see that the gauge on the cap was into the reserve section. I would fuel up. I usually got about 4 gallons in it to top up. The past couple times I have noticed the lamp on and the gauge in the reserve section, but I can only get a shade more than 3 gallons in to top up. Something is happening to my sender. Is it just wearing out? Can I remove it and adjust it a bit? Would I need to replace it to be more accurate?
Meanwhile, I know from setting my trip meter that at 125 miles I need to think about gas. Since that works well, I don't know if I should even bother, but if something has a function, I like it to work properly.

 

[Chopper]

Here are some test you can run on the sender.
THEORY OF OPERATION
With ignition switch ON, the fuel gauge is connected to +12
volts. Current flows through the gauge and variable resistor in
the fuel gauge sending unit to ground. The sending unit float
controls the amount of resistance in the variable resistor.
Inoperative gauges may be caused by three circumstances.
● Sender or fuel gauge not grounded.
● Malfunction in sender or fuel gauge.
● Broken or disconnected wire from ignition switch to fuel
gauge.

1. Remove gauge. Ground Y/W wire of fuel gauge sender
located at bottom of gauge. Turn ignition switch ON.
a. Fuel gauge must indicate FULL. If gauge indicated
FULL, gauge is functioning correctly. Proceed to
step 2.
b. If gauge did not indicate FULL, proceed to step 3.
2. Set MULTI-METER (Part No. HD-35500) to RXI scale to
measure the resistance of the sending unit. Place one
probe on Y/W and the other probe on a good ground.
a. If fuel tank is full, the reading should be 27-40 ohms.
An empty tank should have a 240-264 ohm resistance.
A half full tank will be approximately 97-118
ohms.
b. If a very high resistance or infinity is indicated on the
meter, the sender may be “open” or not grounded.
Check that sender and fuel tank are grounded by
placing one probe of Multi-Meter on sender flange
and the other probe on crankcase. Meter must indicate
one ohm or less. Replace sender if one ohm or
less was present. If a higher resistance is present,
check for poor connection on ground wire.
3. Check voltage to O/W (+) and BK (-) wire of fuel gauge
connector [117] if gauge did not indicate FULL.
a. Correct reading is equivalent to battery voltage.
b. If battery voltage is not present check for broken or
disconnected wire. Replace gauge if wiring problem
is not found.

 

[RickyBobby]

Wow! Thanks Chopper. I'll break out my multi meter and see if I can duplicate the tests. Nice that you have provided at approx ohms I need to see at the different levels too. Much appreciated.

 

[tonyboy59]

Me Too! Ricky! Same issue on 06 fxdwgi 4k miles!