cars

[timmyee]

why does the petrol light come on in the car

[Mattk]

oh please

[Philtaz]

Because it's scared of the dark?

[NetSquirrel]

I don't think they would let you drive, so there's no sense worrying about it.

[New Forester]

Do you mean, how does it work...?

[Kev_UK]

To tell people that they are low on fuel .. keep on driving and the fuel tank will be empty. Why do you ask this question.. has yours come on? Are you one of those people that go to the garage to buy a longer dipstick as the one you have doesn't reach the oil? eh!!

[Clanad]

Another Obliviot?

[New Forester]

Be kind, guys -- there may be a question here somewhere.

[cheyenne]

dont worry?your might get a new one in your stocking at xmas??

[timmyee]

Thankyou New Forester for trying!- I realise my questioning was somewhat careless. I had worked out the bit about low fuel!! What physical process enables the light to come on as the fuel level drops, exposing a sensor above the fuel in the tank I assume?... but how is a circuit then created? But heh..thanks guys for amusing us all!

[jonniekash]

timmyee, Good on ya, at least you came back. Most folk who make a post it seems just never show any interest in whats going on. Good on ya....havagreatweekend

[alinton]

There's a float sensor in the tank. The float er - floats - on the surface of the fuel and has a small rod connected to a potentiometer - a variable resistor (like a volume control). A voltage is applied to one end of the potentiometer, the voltage across it varies with the position of the float. This voltage runs the fuel level indicator, and the car's computer detects when this voltage indicates that the tank is nearly empty and turns the light on.