When I got car low fuel warning light was not working already. I replaced whole unit from junkyard. It was working for couple years and stopped again.
After performing tests as per service manual I have determined that low fuel sensor is shot.
I got another thermistor from the junkyard and it was not working either.
So I decided that I would just get the new sensor and hopefully it would last another 20 years.
I did some research over the internet and discovered that it is actual NTC thermistor (resistor that is changing its resistance depending on temperature), on picture it is steel cylinder.
Replacement-solder out old sensor, solder in new.
Here are new sensor’s properties:
Automotive fuel level sensor fuel pump alarm sensor NTC thermistor
Nominal resistance (25) 1000Ω ± 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
Price: ~$17 CAD (shipping less than dollar) + ~$6 CAD for fuel sending unit gasket from dealership.
Ordered from www.aliexpress.com and had to wait about two weeks.
For those who are interested how low fuel sensor is working:
There is constant 12v through the sensor. Because it is actually resistor it is getting warm but when gasoline level is high and sensor is submerged into fuel- sensor’s temperature is the same as fuel and its resistance is about 1000 Ohm, when fuel level dropped below thermistor-fuel does not cool its anymore and its resistance decreases and warning light comes up.
Hope that it helps someone.