Going round in circles fixing nav light!

[acraw]

I’ve one of the folding pole navigation lights on the transom.
It’s not worked since I’ve owned the boat, so it’s raining, so into the garage I went to try and fix it.
Switch was a bit corroded, fixed that.
Checked for 12V at bulb terminal. Good.
Checked other bulb terminal back to battery earth. Beep good.
Bulb in, nothing?
Any ideas?
Does it matter if I am using car bulbs?

[neil.mccrirrick]

Check the fitting. It’s probably spring loaded. Even though you are getting 12 volts if the terminals aren’t reaching the bulb. Nada.

[jwalker]

If you've got high resistance in the cable, you'll read 12v on your meter but the bulb won't be able to draw the required current through the cable. Get the bulb online and then check the voltage, if it's low you've got a wiring problem.

[Pikey Dave]

Does the cable bend where the pole folds? Could be broken internally.

[acraw]

Thanks all I think it’s a wiring issue and not enough current.
Will have to be put in the to do over winter list.

[spartacus]

You should be thinking of switching to LED lights too.
https://boatlamps.co.uk

If you're rewiring, opt for tinned cable.

[IainK]

Hi Acraw, a painful session that I have endured to only see the error or my ignorance after a few hours of testing. Car bulbs use the outer metal case as a theatre or ground: marine bulbs don't but ONLY use the two solder buttons on the bulb end. Use marine bulbs, in LED if you wish, and problem should solved.
Best wishes Iain

[jonp]

Unfortunately small exposed boats are always going to suffer from the elements, for simplicity I changed over to these https://www.railblaza.com/products/navipack/

[acraw]

Originally Posted by IainK

Hi Acraw, a painful session that I have endured to only see the error or my ignorance after a few hours of testing. Car bulbs use the outer metal case as a theatre or ground: marine bulbs don't but ONLY use the two solder buttons on the bulb end. Use marine bulbs, in LED if you wish, and problem should solved.

Best wishes Iain

Interesting, I wondered that but I am sure the connection is via the outer case, there’s only one spring contact in the middle

[Last Tango]

This isn't a "car vs marine" thing.

It depends on the type of bulb. Some use a center pin with the base as the return others use two pins on the bulb. Double filament (brake/side light) have two pins one for each filament and a return via the base as well.

Can't help but think we're making a mountain out of a mole hill here.

If you were local we could sort this in two minutes.

[acraw]

[emoji23] this is why these things are frustrating Maybe I’ll just ring Force 4 as it is one of these https://www.force4.co.uk/media/catal...1/0/100957.jpg

[paintman]

Originally Posted by jwalker

If you've got high resistance in the cable, you'll read 12v on your meter but the bulb won't be able to draw the required current through the cable. Get the bulb online and then check the voltage, if it's low you've got a wiring problem.

This.
If the wiring is corroded a digital multimeter will show battery(ish) voltage present but insufficient current is able to pass. Had this with my RRC when the in-tank petrol pump stopped working. Corrosion in the wiring harness at the connector was the cause.
I'm given to understand an analogue meter would have shown this up but a digital one won't. Whether that's right or not I don't know.
In my case a 12 volt test bulb with a pin pushed through the insulation revealed the point at which the wire was good.