12v Bulb Testing

[sailingjupiter]

Both bulbs in my mast head unit aren't working so I have bought conventional replacements. Thought I would test them both before I fit them - just in case. One I got as a 24V by mistake so trip back to chandlers but the other one I have tested but doesn't appear to work.

Am I correct in saying all you need to do is connect a small wire onto both terminals of a 12V battery then hold the negative to the bulb holder and touch the positive wire on the base pin of the bulb? If so it aint working. Have I done this right? Maybe it's a faulty bulb in which case I'm glad I tested it! Please could someone clarify. Did a test with another bulb and it did work. Just wondering if it might be the type of bulb (is it a festoon for a Aquasignal masthead 40 series - I think) that may be a little different. The filament is intact as you can obviously see it.

Many thanks

 

[sailorman]

Both bulbs in my mast head unit aren't working so I have bought conventional replacements. Thought I would test them both before I fit them - just in case. One I got as a 24V by mistake so trip back to chandlers but the other one I have tested but doesn't appear to work.

Am I correct in saying all you need to do is connect a small wire onto both terminals of a 12V battery then hold the negative to the bulb holder and touch the positive wire on the base pin of the bulb? If so it aint working. Have I done this right? Maybe it's a faulty bulb in which case I'm glad I tested it! Please could someone clarify. Did a test with another bulb and it did work. Just wondering if it might be the type of bulb (is it a festoon for a Aquasignal masthead 40 series - I think) that may be a little different. The filament is intact as you can obviously see it.

Many thanks

try it but not in the holder (it doesnt matter with a bulb if the wire are swapped). hold one wire against the outer body then flash the other onto the centre pin.
just a thought does the Aquasignal 40 bulb have 2 pins on the bulb base

 

[VicS]

just a thought

I should think so too.

Normally one would expect a nav light bulb to have two base contacts and the body (cap)not to be connected.
Certainly so for an Aquasignal bulb

Therefore test with atwire to each of the base contacts (taking care not to short out the battery)

 

[sailorman]

I should think so too.

Normally one would expect a nav light bulb to have two base contacts and the body (cap)not to be connected.
Certainly so for an Aquasignal bulb

its yrs since i have changed one

so the OP holding a wire on the holder wont work then

 

[sailingjupiter]

Thanks for the replies.

What an idiot i am. Now when trying one wire on each pole they work - even the old ones that didn't work when in their holder on top of the mast. Another wast of £15 for new bulbs.

So thats a new problem I have got. Why won't they work in situ? I tried my multi meter and there was definitely 12V showing when switched on. So the problem must be something to do with the connectionfrom there to the bulb holder.

They are the 40 series I think. The one that is quick fit where you push fit then use the plastic collar to secure them.

Any ideas?

 

[sailorman]

Thanks for the replies.

What an idiot i am. Now when trying one wire on each pole they work - even the old ones that didn't work when in their holder on top of the mast. Another wast of £15 for new bulbs.

So thats a new problem I have got. Why won't they work in situ? I tried my multi meter and there was definitely 12V showing when switched on. So the problem must be something to do with the connectionfrom there to the bulb holder.

They are the 40 series I think. The one that is quick fit where you push fit then use the plastic collar to secure them.

Any ideas?

clean the contacts up a bit
spares are always useful even if you dont use them i have spares for spares.
i should have remembered they are 2 pole as i took mine out 3 weeks ago to check it as the mast has been struck

 

[morgandlm]

Mast head lights

The problem may be poor contacts or corrosion in your supply cables. I had a similar problem a few years ago and found that the supply wire cores at deck level were badly corroded. Testing with a meter showed continuity but the corrosion prevented sufficient power even to light a bulb.
Morgan

 

[PetiteFleur]

The problem may be poor contacts or corrosion in your supply cables. I had a similar problem a few years ago and found that the supply wire cores at deck level were badly corroded. Testing with a meter showed continuity but the corrosion prevented sufficient power even to light a bulb.
Morgan

I had the same problem a few years back and replaced all the cable with proper tinned stuff - expensive but not had a problem since.