I don't think I imagined this... but I'm pretty sure the fuel warning light came on for a few seconds the other day when I had more than half a tank left - and the car may have shuddered slightly.

What could this be? Fuel blockage? Is there anything I can do to check it out? (I get bad fuel economy by the way... could be related)

Cheers,
Kim

Kim, the low fuel light is a thermistor located in your fuel tank toward the bottom and whilst submerged in fuel keeps the fuel light off. As the fuel goes down it comes out of the fuel and brings the light on, so if yours came on with half a tank then it maybe on the way out or there is a fault in the wiring.

For those interested a thermistor is a type of resistor that heats up according to current flow (yes all resistors heat up) and the type used has a negative temperature co efficiant which means as temp goes up resistance goes down more current flow. While it is submerged, the fuel keeps it cool, keeping resistance high and practicaly no current flow to earth. Once it is exposed it heats up the resistance goes down allowing more current to flow heating it further dropping resistance, more current flow illuminating the light.
This is why the light fades in and out and comes on when on certain angles with a nearly empty tank.

Thanks Phil. I've noticed on an almost-empty tank as well, that idling at lights or something for a minute or so will make the light come on.

Ill have to keep an eye on it and see if it comes on again with a half-empty tank - wonder how hard it is to replace, if it is faulty.

Thanks,
Kim

I've noticed mine will go on and off anywhere between empty and 1/2 but then I don't find the fuel gauge terribly accurate anyway.

Thanks for the explanation of the fuel sensor Phil. At first I was thinking.. a thermistor? hah.. but then I realised how it'd work as per your explanation.

I just wish they were more accurate. The glow of the light as it turns on and off though is pretty cool :)

It's funny when people get in my car and say 'Man you need fuel.. you sure we aren't gonna run out?' and then rather than tell them that it comes on at 1/4 tank which is a tad silly, I just shrug and keep on driving..

can anyone tell me wether the low fuel light in a TH is controlled by a computer or if it is by the same method?
it just seems as though there is no logic to when it comes on..
i also remember reading a post about how someone seemed to "train" the low fuel light to come on later rather than sooner..?!

Kim: My TR does that at the lights or idling (the fuel light come on thingy) then when I start moving again it goes off! I just put it down to crappy fuel level detection methods...

well mines even crappier, it just doesnt come on at all. and usually i do about 100ks for my gauge to show a half empty tank and then i do another 300ks on the last half. ive never had the fuel light go on even when ive put in 61L of fuel.

GuRu

The TH is the same, most cars any make use this setup, as for training it to come on early from my understanding of this type not easily, you would have to physicaly move the thermistor down in the fuel.
On my TP the light didn't work so I pulled the sender unit and the thermistor (stuffed and would of had to replace entire unit) was fitted to that, spose you could move it down don't remember 7 odd years ago.

pseudomorphous

Simple check would be to earth out the feed wire from the low fuel light at the sender unit, key in ign position. If it lights the unit is faulty if not could be bulb, fuse or wiring.

its not like it really bothers me anyway.
i know how many k's i can get from a tank so i simply fill up when i get there. having the light or the lack of doesnt bother me in the slightest. not to mention its too much work for too little gain.