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warning light

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commoner | 15:16 Thu 01st Nov 2012 | Motoring
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My Grande Punto 56 plate has a warning light on the dash which indicates a bulb failure...............all the lights including indicators are workung correctly but this light comes on and stays on when I start up even when I have no lights on at all....any ideas please what the cause of this could be?

Thanks for any comments ;-)

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Check the bulb contacts aren't slightly corroded, especially in the unit that gets condensation. the slightly higher resistance from a corroded contact can be enough to trigger the warning but the bulbs still work.

(I used to get just this happening on the back of my car until I cleaned the bulb bases and the contacts in the light fitting)
17:08 Thu 01st Nov 2012
Comm, is there a light in the boot which isn't working? Interior light not coming on?
Question Author
Hi alba...Everything is working normally...every light even the reg plate light works....only thing is that I noticed condensation forming inside the passenger rear light cluster occasionally but it seems to clear itself after a while.

Can't figure out why the warning light comes on as soon as I turn the key to the first position even wwith no lights turned on...scary!
Comm, I've absolutely no idea. Sorry me dear. x I could only suggest the silly questions which Mr A would ask me :-)
Maybe there's a dodgy connection somewhere but the lights are working and not telling the warning light to shut up?
Check the bulb contacts aren't slightly corroded, especially in the unit that gets condensation. the slightly higher resistance from a corroded contact can be enough to trigger the warning but the bulbs still work.

(I used to get just this happening on the back of my car until I cleaned the bulb bases and the contacts in the light fitting)
Question Author
lol..you really are an angel on AB.....always ready to have a go..thanks luv..I'll get to the Fiat place tomorrow x
^^ see, a man what knows :-D
(us women can't park a car either!)
Question Author
Thanks chuck I must check that out...getting too late now but as soon as I can I'll get to it....I thought that light was to warn you a bulb was actually out...but obviously not as all my lights are working.
the warning light works by measuring the resistance in the circuit the bulbs are on, if the resistance goes outside a pre-set limit the warning light comes on.

Obviously if a bulb fails the circuit goes totally open, which is outside the limits set so on comes the warning light (expected behaver)

But having a bad contact on one of the bulbs, or a bad earth connection for the light cluster can also put the resistance of the circuit outside the limit set, so on comes the warning but all the lights will be working.

As you are getting condensation in one of the clusters the chances are that this has caused the contacts on the bulb to corrode, which is exactly what happened on my car, I had to clean all the contacts and split the light cluster apart and re glue it back together so it was sealed properly.

It could still be a bad earth causing yours, but contacts are where I'd look first.
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Thanks for that chuck.....always nice to learn something new :-)
Question Author
Hi Chuck..checked out the contacts and found they were corroded...not badly but bad enough to cause the problem...manage to get a needle file onto them and everything now works just great...
Thanks again..great stuff..;-))

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