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Discussion Starter · #1 ·
I have a intermitted fuel light issue. I ran out of gas twice now and no fuel light on at all. This happened at different times, so sometimes it work and other times it don't. I normally use mileage as an indicator but I had changed the battery so I loss the used mileage. Any suggestions besides when in doubt filler up.
 

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02-03 1800S LED fuel indicator.

Open the 3 pin connector near the fuel tank for the fuel sensor/fuel pump.
Ground the Brown/Black wire going to the cable harness, Switch on the IGN.
The indicator should light up within 90 seconds.

if the indicator illuminates, it means the sensor has expired.
A thread in the how to Step by Step 1800 fuel sensor repair.

If sensor is defective, a 1k varistor could be obtained to replace the device in the
metal can, or as Fastspek did was to buy the sensor in the can.
 

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2002 VTX 1800C, red
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Thermistor in the can, AliExpress, ordered 3 December, $8.55. Vendor JIALAN1698 Store. Arrived today 15 Dec. This will go in my box of spares. Just wanted to see if Alibaba listed it and how long it would take to get here.
 

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Discussion Starter · #8 ·
I grounded out the brown/black wire of the 3 pin connector and the light comes on quick. I replace the resistor like the one that the guy in the link that Hans posted . The light still doesn't come on. I checked the continuity of the resister prior to install and it was 1.748. I installed it and twisted the lead from the resister to the incoming brown/black wire to connector. I tested continuity again with a meter and got the following

brown/black to twisted connection ( wire from resistor to wire that was cut from old resistor going to 3 pin connector ) read out to .02

Twisted connection to Ground pin in connector read 1.748

Twisted connection to Brown in connector read 1.749. I assume that it the gound side of the pump and it's grounded to the assembly, therefore going through the resistor.

I plugged the 3 pin connector in and turn on the ignition, the fuel pump ran as expected and I waited over 2-3 minutes and still no light. I attached a ground from the engine case to the twisted connection and the light comes on.
I bought 3 resistors and they read the same.
 

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duffer, you mention you purchased a resistor not a thermistor. Is that just a typo? The readings across the two wires of the new component should be close to 1000 ohms. Is the 1.749 actually 1,749 ohms? If the reading you are getting is actually 1749 ohms then it maybe too high a value to begin with. It should be closer to 1000 (1K) ohms.
An easy way to test your thermistor is to connect the two wires to your multimeter, set on the ohm scale, and make a fist around the thermistor and see if the value starts to drop.
The old thermistor needs to be cut out of the circuit and the new one connected to the two wires that remain. The thermistor will then be in series with the warning light. With the ignition turned on current will pass through the thermistor on it's way to the warning light, but not enough to light up the bulb. As the thermistor starts to warm up the resistance value will start to fall and more current will pass through. This will allow the warning light bulb to illuminate. Once the thermistor is immersed in a liquid (gasohol in this case) the heat generated by the thermistor will transfer to the liquid keeping it cool and not allowing enough current to light the warning light.
 

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It has to be a 1k Thermistor. (1000 ohms)
It has to be a fuel or oil related thermistor.





Ochoos Automotive Fuel Level Sensor Fuel Pump Alarm Sensor NTC thermistor Fuel Sensor: Amazon.com: Industrial & Scientific
Ochoos Automotive Fuel Level Sensor Fuel Pump Alarm Sensor NTC thermistor Fuel Sensor: Amazon.com: Industrial & Scientific

www.amazon.com



Automotive fuel level sensor fuel pump alarm sensor NTC thermistor Fuel sensor
Nominal resistance (25) 1000 ± 20%
Detection time: 180sec max
Saturation: 60mA max
Rated Voltage: DC 12V
Operating Volts: DC 8 ~ 16V
Operating temperature range: -40 ~ -80
Light is irradiated: 135mA min
not irradiated with light: 60mA min
$12 dollars, still a rip off.
 

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It has to be a 1k Thermistor. (1000 ohms)
It has to be a fuel or oil related thermistor.





Ochoos Automotive Fuel Level Sensor Fuel Pump Alarm Sensor NTC thermistor Fuel Sensor: Amazon.com: Industrial & Scientific
Ochoos Automotive Fuel Level Sensor Fuel Pump Alarm Sensor NTC thermistor Fuel Sensor: Amazon.com: Industrial & Scientific

www.amazon.com



Automotive fuel level sensor fuel pump alarm sensor NTC thermistor Fuel sensor
Nominal resistance (25) 1000 ± 20%
Detection time: 180sec max
Saturation: 60mA max
Rated Voltage: DC 12V
Operating Volts: DC 8 ~ 16V
Operating temperature range: -40 ~ -80
Light is irradiated: 135mA min
not irradiated with light: 60mA min
$12 dollars, still a rip off.
The OP bought the same sensor like me. I got about the same value when measuring the resistance: 1750 Ohm. The value of 1000 Ohm is obtained in a test setting. In that case the sensor is immersed in a liquid while connecting the sensor to a 12 V power source.
I grounded out the brown/black wire of the 3 pin connector and the light comes on quick. I replace the resistor like the one that the guy in the link that Hans posted . The light still doesn't come on. I checked the continuity of the resister prior to install and it was 1.748. I installed it and twisted the lead from the resister to the incoming brown/black wire to connector. I tested continuity again with a meter and got the following

brown/black to twisted connection ( wire from resistor to wire that was cut from old resistor going to 3 pin connector ) read out to .02

Twisted connection to Ground pin in connector read 1.748

Twisted connection to Brown in connector read 1.749. I assume that it the gound side of the pump and it's grounded to the assembly, therefore going through the resistor.

I plugged the 3 pin connector in and turn on the ignition, the fuel pump ran as expected and I waited over 2-3 minutes and still no light. I attached a ground from the engine case to the twisted connection and the light comes on.
I bought 3 resistors and they read the same.
Did you install the sensor in the bracket before testing? If not the sensor is not grounded and the light will not come on. The 3 sensors that I bought had about the same reading like yours (1750 Ohm) and everything works fine:

1800 Fuel Pump info several PDF docs, Fuel Tank Sensor replacement | Honda VTX Forum (vtxoa.com)
 

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You three guys are a tremendous asset to this site with all your knowledge. I for one am in awe. Merry Christmas!
 
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Discussion Starter · #13 ·
The OP bought the same sensor like me. I got about the same value when measuring the resistance: 1750 Ohm. The value of 1000 Ohm is obtained in a test setting. In that case the sensor is immersed in a liquid while connecting the sensor to a 12 V power source.

Did you install the sensor in the bracket before testing? If not the sensor is not grounded and the light will not come on. The 3 sensors that I bought had about the same reading like yours (1750 Ohm) and everything works fine:

1800 Fuel Pump info several PDF docs, Fuel Tank Sensor replacement | Honda VTX Forum (vtxoa.com)
I tested it before and after. As you see in the write the resistance is the same when installed and testing through the pins. The pump motor side and the ground. I will test it again and clock the time. It says max 180 seconds detection so I'll double check.
 

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When the Thermistor is submerged in gas, the resistance stays high.
There is a small amount of current on all the time when Ignition is on.
When the Thermistor is exposed, the temp rises and the resistance lowers.
Less resistance -- more current--indicator light ups.
1800C has an incandescent lamp and the Thermistor.
The other 1800 models with Led indicators have a resistor to create
the same current as the lamp version does.
 

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Discussion Starter · #16 ·
Ok here is what is happening
First Pic is when it is submerged in water with key off notice ohms pics.
Second pic is with key on and then removed from water. Pic shows in water but I removed it and waited 2 minutes and no light and stayed at OL
Hood Motor vehicle Automotive lighting Automotive design Automotive tire

Motor vehicle Automotive tire Bumper Gas Automotive lighting
Motor vehicle Automotive lighting Hood Automotive tire Automotive design
Motor vehicle Automotive tire Bumper Gas Automotive lighting

Third is after key is switched off.
 

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Ohms is for testing continuity with NO external power no external voltage.
You can test for amps or milliamps with external power (IGN sw on) meter in series with sensor.
Best thing is to wire the Thermistor, one wire to Green-Ground, the other wire to Br/Bl.
Now turn the IGN sw and see if if indicator will light up.
It does not need water, it will heat itself if it has current flow and indicator will light up.
.
 

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I wonder if the bracket of the sensor has a bad ground since you wrote this: I attached a ground from the engine case to the twisted connection and the light comes on.
This means that the sensor is ok.
 

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Discussion Starter · #19 ·
Hans, your right AGAIN. I waited the said 3-4 minutes and it did come on. Either my memory or eyes or both is going because I read 80 seconds and someone said 90 so I timeed it for 120. Looking at the description of the sensors again it says 180 seconds max. Hopefully my errors will prevent others from turning the key off too soon.
Thanks to all that replied.
 
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