| Author | Message | ||
     Doz |
just picked up an 05 xb9sx and have no shop manuel or wiring diagram. ran out of gas today and the low fuel light never came on and the trip meter never came on either.where do I look and what color wires do I need to trace? And I'm out of town in unfamiliar territory | ||
| Akbuell |
I only have an '08 manual, so the wire colors May Not be the same. The low fuel level sensor is part of the fuel pump assy. The plug to the fuel pump on an '08 has 4 wires. Bk is ground. O/GY is power from the battery-fuse block. BN/Y is the control wire from the ECU. Y/R is the wire to the low fuel light/instrument module. A quick check could be to take a 9V dry cell battery and some jumper wires, and connect the neg terminal to ground, the pos terminal to the Y/R wire. If the low fuel light comes on, the problem is most likely the sensor, not the light bulb or the instrument module. Hope this helps, Dave | ||
| Doz |
Thanks Dave, I'll give that a try | ||
| Rays |
The low fuel sensor is an NTC Thermistor that has power supplied from the Instrument Cluster. With fuel covering this thermistor it is kept cool. When the fuel level drops enough the exposed thermistor can heat up and the resistance drops and triggers the low fuel light. This is from the '06 Manual for my X but it looks like the wire colours for the fuel pump are the same for the XB9.  The fault finding steps in order of ease are as follows: With the ignition switched off disconnect the fuel pump connector and connect a ground to pin A. You could jumper pin B to pin A but be careful not to short out the fuel pump power. This is the bike side side connector on my X - pin A is bottom R/H. Pin B is bottom L/H.  An insulated small alligator clip works well on these flat pins and takes away the shorting risk with the insulation pushed right down.   Turn the ignition and ground that pin (battery negative terminal is a reliable spot close by). There is hysterisis built into the circuitry to stop the light flashing with fuel slosh so it takes some time for the low fuel light to come on ( I just tested this on my XT and it was about 8 secs). If the light doesn't come on doing this you have either a wiring issue to the instrument cluster or a faulty instrument cluster. The light isn't a bulb for this function so let's hope that isn't your issue. If the light does come on then the thermistor mounted in the fuel pump assembly (or the wiring associated with that) is faulty. Measure the resistance between pins A and B on the disconnected fuel pump (the fuel sensor to ground). This should be between 850 and 1200 ohms according to the XT manual - I believe this sensor is common across the early XB's at least. On my XT it measures at 1075 ohms. If that measures significantly higher or open circuit then that will require the fuel pump to be removed. The sensor can be readily replaced once that is done but it may require a bit of work to remove the pump. I have had the pump out of both my X and my XT and that can be done without removing the swing-arm pivot but on an XB9 I don't think that is possible but I don't know for certain. | ||
| Desert_bird |
Any idea where I can get a new thermistor? I pulled the fuel pump off my 08 XB after my low fuel light stopped coming on at all. Wires and connectors all seem OK and I have confirmed that the light does come on by grounding pin A. I think the resistor is dead. DB | ||
| Reepicheep |
Disconnect it and measure it with a decent multi-meter on the Ohm setting. You should be able to see it change with temperature if it is working. | ||
| Desert_bird |
Only reading I get is between 047 in ice water and 035 if I hold the sensor in ambient air in my hand. One lead of multimeter to the body of the sensor and other to the wire coming off the sensor. The low light came on once (!) when I connected it back up to the harness on the bike, but didn't come on again. I dipped the sensor in cold water and heated it up again. It seems really finicky. That can't be correct. I've found a few thermistors from sites in China that are designed to use in vehicles. Most are just the resistors, so I'll need to open the metal housing and replace the wafer itself. Then there are things such as this: http://www.aliexpress.com/item/Automotive-fuel-level-sensor-Fuel-Pump-Fuel-low-oil-level-alarm-sensor-thermistor/32393580397.html?spm=2114.40010208.4.67.0CyaNa Are they all rated similarly? What is the wattage on the stock low fuel bulb? Seems like a big hassle. Surprised that HD does't provide the thermistor unit separately to just plug in. DB (Message edited by Desert_bird on March 19, 2016) (Message edited by Desert_bird on March 19, 2016) | ||
| Reepicheep |
The thermistors values (normal resistance at 70 deg C I think) and types (increasing or decreasing resistance with temps) are all over the map, and the ECM is expecting a particular one. You might get lucky in that it is a really common one everybody uses (10k with a negative coeficient I think). But maybe not. Or there might be more to the low gas thermistor in this application. In other words, I'd be chasing the factory part or signing up for a good engineering project (that would likely start with chasing the factory part). | ||
| Froggy |
Buell part number P0789.KA for a new sensor, about $15. (Message edited by Froggy on March 19, 2016) | ||
| Desert_bird |
Shucks, I always hate to be saved from a "good engineering project." Thanks fellows. | ||
| Reepicheep |
Thanks for the thread and details all, my new to me XT just lost the low fuel light. But now I know the fuel tank is exactly 3.93 gallons, plus about 6 oz.  I haven't dug into it yet to check if it is just a bad connection, a blown bulb, or a dead thermistor. But I always start with the knowledge vault, and I appreciate people taking the time to document their knowledge and experience here. |
