Both navigation lights not working, 6v?

[wvansl]

Hej!
I bought a Dufour 36 classic and my navigation lights (bow and stern) are not working.
I cleaned the connectors (a bit corroded but not excessive) and I still only measure somewhere around 6v-7v.
At the switchboard, I measure 12v.

This is my first boat so I would like some confirmation that the lights are really supposed to be 12v and not by any chance 6v. Checked the light bulbs and normally they always say how many watts and volts it is supposed to be but I can't read it.

Thanks very much!

 

[Parabordi]

The wires are probably all corroded inside which causes a resistance and hence voltage drop, i have the same issue on mine. You maybe lucky and able to re-strip the wires at each end and clean up with sandpaper, if not, you may need to run new wires (as i am)

 

[Stemar]

You are correct - they should be 12v. Somewhere there's another corroded connection, which means your introduction to the joys of winter projects is to go through the boat, checking and cleaning every connection you can find because, where there's one bad contact, there are almost certainly others lurking and biding their time to let you down at an inconvenient moment.

Relax - it isn't nearly as bad as it sounds!

 

[Supertramp]

+1 for the previous comments. I had this, traced the wiring, cut it 9 feet back and tested. The drop was in the wire, not connections. Removal showed blackening for 6 feet or so back from the bow. The challenge may be accessing a factory built in wire run. Replace with tinned wire.

 

[wvansl]

Great! Thanks for the answers. I already thought it would be 12v and the problem would be inside the wire itself but now I'm sure it was not 6v by any chance!

I will cut back the wire and measure if I hit 12v somewhere. Thanks!

 

[david_bagshaw]

Great! Thanks for the answers. I already thought it would be 12v and the problem would be inside the wire itself but now I'm sure it was not 6v by any chance!

I will cut back the wire and measure if I hit 12v somewhere. Thanks!

dont forget you need to measure the 12 v with a running bulb connected to it, as the wire needs to deliver some amps, not just the millli or micro amp a voltmeter takes

 

[Stemar]

The challenge may be accessing a factory built in wire run. Replace with tinned wire.

Tinned is definitely better, but there are a lot of old boats around that were fitted out with ordinary wire. The trick - far from foolproof, but it works most of the time - is to use the old wire to pull the new one through the inaccessible bits.

 

[Gsailor]

Don’t cut the wire back too much - you are imho going to need to pull new wire through - because the easiest method to pull a new wire through is by securing it to the old wire and pulling through. Edit: just noticed Stemar already said that.

Another edit- if you change from old filament bulbs to LEDs you will hopefully find less amps are needed and then you can use a thinner wire to pull through and change the fuse or circuit breaker protecting that wire - might make pulling a new wire through easier- do the sums carefully though - the wire must be thick enough to carry the current draw or you will melt the wire and potentially have a fire (or have the fuse blowing all the time - preferable to a melted wire, but you will not get the LED to stay on)

But if you do use thinner wire, and switch to LEDs, you will never be able to use filament bulbs again because they will attempt to draw a greater current and blow the fuse every time.

Unless interior panels are very easy to remove - I don’t know your boat enough to know how good access is to the wiring. Sticking with same size wire would be best - ideal world you will have enough access to wiring not to have to pull through.

 

[jbweston]

dont forget you need to measure the 12 v with a running bulb connected to it, as the wire needs to deliver some amps, not just the millli or micro amp a voltmeter takes

This is important for anyone having a lighting problem but still measuring 12v at the bulb socket with a meter. The OP won't be tempted to fall into the trap of thinking 'it reads 12 volts on my meter so it must be OK' as he's only getting 6 volts, but years ago the 12v on the meter had me scratching my head until the penny dropped - 12 volts at almost no amps can pass along an almost useless corroded cable.

 

[William_H]

Don’t cut the wire back too much - you are imho going to need to pull new wire through - because the easiest method to pull a new wire through is by securing it to the old wire and pulling through. Edit: just noticed Stemar already said that.

Another edit- if you change from old filament bulbs to LEDs you will hopefully find less amps are needed and then you can use a thinner wire to pull through and change the fuse or circuit breaker protecting that wire - might make pulling a new wire through easier- do the sums carefully though - the wire must be thick enough to carry the current draw or you will melt the wire and potentially have a fire (or have the fuse blowing all the time - preferable to a melted wire, but you will not get the LED to stay on)

But if you do use thinner wire, and switch to LEDs, you will never be able to use filament bulbs again because they will attempt to draw a greater current and blow the fuse every time.

Unless interior panels are very easy to remove - I don’t know your boat enough to know how good access is to the wiring. Sticking with same size wire would be best - ideal world you will have enough access to wiring not to have to pull through.

Except on a boat thicker wire means more robust and likely last longer in corrosive atmosphere. Go heavy. ol'will

 

[wonkywinch]

This is important for anyone having a lighting problem but still measuring 12v at the bulb socket with a meter. The OP won't be tempted to fall into the trap of thinking 'it reads 12 volts on my meter so it must be OK' as he's only getting 6 volts, but years ago the 12v on the meter had me scratching my head until the penny dropped - 12 volts at almost no amps can pass along an almost useless corroded cable.

6v across a 12v bulb means the internal resistance of the circuit, inc cable, is near identical to the bulb.

I'd also check the switch. It's common for contacts to corrode. Easy test, check if there is any voltage across it when switched on. Should read zero.

 

[PetiteFleur]

And make sure you use Tinned copper wire for any replacement wires.

 

[Rhylsailer99]

Mine was kind of the same, except I got 12v but as soon as a load went on the volts dropped. A complete rewire fixed all my problems.

 

[Refueler]

OP has my sympathy .... my new acquisition ... yard had rewired the boat so nav lights (P + S) stern and mast steamer all came on one switch. How a yard could be so stupid ??

Anyway ... took us ages to sort out ... but finally found that the dual P + S nav light under the pulpit had TWO power cables top it ... one was more than enough - but they had installed TWO white cables twisted together which disappeared into conduit with load of other wires ... other end black cables exited not twisted together ...
Took ages to determine which was mast steamer ... that was then connected to a redundant switch ...

All I can say - is that I can power a lighthouse up front based on the cabling !!

All will be LED anyway for next season ... with the old filament bulbs as back up in the locker.

 

[NorthUp]

Was the previous owner a bodger? Maybe two lamps are wired in series instead of parallel.

 

[Refueler]

Was the previous owner a bodger? Maybe two lamps are wired in series instead of parallel.

Prev owner didn't work on the boat - he gave all work / maintenance to the yard.