WHY DOESN'T THE LIGHT WORK?

alisdair4

alisdair4

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Isle of Bute
midnightdrifter.net
WHY DOESN\'T THE LIGHT WORK?

So, first trip of the season on Midnight Drifter. Driving into Holy Loch, (after a respectable sail from Rothesay). Say toSWMBO - put on the side lights (ie motoring) and the steaming lights, my dove!". Of course, the bloody steaming light doesn't come on. Alongside, following day, I check the fuse (OK), voltage at connection to mast foot (OK) bulb at 7m above deck(ok) .The light worked last week with the boat on the hard, and nothing has changed. Any ideas?
 
Re: WHY DOESN\'T THE LIGHT WORK?

Other than checking the voltage all the way through, the only other way is to do the usual visual connector/deck fitting checks.
 
Re: WHY DOESN\'T THE LIGHT WORK?

[ QUOTE ]
Other than checking the voltage all the way through

[/ QUOTE ] BUT be aware that if you check with a digital multimeter you can often get a normal reading though a bad contact (been there, got the T shirt) There is much in favour of checking with a bulb soldered onto a couple of leads. That won't light if connections are bad.

But check for continuity up the mast and through the bulb with a meter on a low ohms range. If its a 25 watt bulb you are only expecting less than half an ohm any more then there is a poor connection somewhere.

Check the supply at the base of the mast with the aforementioned bulb.
 
Re: WHY DOESN\'T THE LIGHT WORK?

Probably not enough crew on board.
Old Chinese proverb say " Many hands make light work" /forums/images/graemlins/smile.gif
 
80% probablity

is corrosion at the bulb-holder,

try a new (10watt?) bulb and a squirt of contact cleaner lubricant, unless you enjoy cavorting around 9m above the water.

My lower forward nav lights do it regularly, even though there's no discernible water ingress.
 
Re: 80% probablity

1.Break the conection at foot of mast.
2.Feed 12v into the bulb from here from a battery.
If it works
3.Check that you have a 12v circuit coming into the foot of mast with bulb or multimeter on the two wires. (not just live in, but neutral out)
 
Re: 80% probablity

[ QUOTE ]
Sorry to be pedantic but if checking the continuity then look for a resistance of 6.5 ohms

[/ QUOTE ] Sorry yes you are right i should have said 6 ohms. In fact when a filament is cold it has a somewhat lower resistance than you calculate from the volts and the watts. Not as low as 1/2 ohm though.!

A 10 watt bulb will have a resistance somwhat less tha 14 ohms
 
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