Fiesta Mk3 fuel gauge- How does it work?

The fuel gauge in my MK3 1.1L Fiesta still reads the level in the tank after switching off the ignition. If I top up the tank the needle does not show the increase until the power is switched back on so it does need power to read the tank level

I've never had a car that does this. How does the gauge 'remember' with the power off?

Any ideas?

TIA

Bob

Reply to
Bob Minchin
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I think the gauges are an air core meter type instead of the usual bi-metalic or magnetic type. My Toyota does the same.

Reply to
Chris

... and so does my daughter's 10-year old Micra. I wish mine did it!

Reply to
Richard Murphy

There's no hairspring to return the needle to zero, and the needle itself is damped. So when the ignition is switched off, it doesn't actually 'read' the level. It simply stays where it was. When you fill up and switch the ignition on, the guage reacts to a difference in current from the sender, so moves and holds the needle in the appropriate position. As the current changes between full and empty, the needle simply follows the changes. Mike.

Reply to
Mike G

It's a bit disconcerting if you're not expecting it. The first car I drove which had this feature was a firm's Sierra back in 1989. There I was waiting for the ferry from the Isle of Wight when I noticed the fuel gauge was stuck. I had to plough through the handbook to find out why.

-- Malc

Reply to
Malc

Thanks for the relies chaps. What dont really understand is why the needle does not slowly drift in one direction or the othe. OK it might not have a return spring but is it fitted with an anti gravity device?? Maybe it just has a nasty sticky bearing?

Bob

Reply to
Bob Minchin

The message from "Bob Minchin" contains these words:

Very thick grease. Stuff called Kilopoise a grease with an centipoise rating up in the thousands, used for making potentiometers move smoothly.

Also, if the needle's mass-balanced then it won't feel the urge to move unless you rotate the dashboard around the needle's axle - which is unlikely.

Reply to
Guy King

And if it _is_, you're probably not worried about the fuel gauge at that particular instant.

Pete.

Reply to
Pete Smith

The message from Pete Smith contains these words:

Bugger - I've rolled into a ditch /and/ I'm out of fuel.

Or worse - Bugger - I've rolled into a ditch /and/ I've got a full tank.

Reply to
Guy King

You're such a pessimist. :-) Mike.

Reply to
Mike G

The message from "Mike G" contains these words:

OK - "I was upside down in a ditch, but couldn't be arsed to get out 'cos I was debating whether the tank was half full, half empty or glugging round my head"

Reply to
Guy King

Whats the advantage of this system? - besides letting the TWOCKers know you have a full tank.

Bill

Reply to
Bill

The message from "Bill" contains these words:

So you can see how much fuel is in the tank without having to turn on the ignition, of course.

Reply to
Guy King

Pointless, IMHO, as the previous poster says, it only makes your car more attractive to joyriders if it's showing full.

Reply to
SteveH

The message from snipped-for-privacy@italiancar.co.uk (SteveH) contains these words:

I can't see joyriders taking a Montego diesel with the footwells full of litter and banananana skins in the first place. Anyway - it might not be showing full - mine rarely is.

Reply to
Guy King

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