Pre-mature Nav Bulb Failure

[Sailing Steve]

I have changed the forward nav light bulb three times in the last the year.  In that time, I've only had the nav lights illuminated maybe for a couple of hours total.  When I replace the bulb, there are no signs of water having entered in behind the lens, wetting the bulb, so I am at a loss why the bulbs are failing so frequently, and with such very little use.  The aft nav light is the same bulb and lens model, and I've yet to replace it. This leads me to believe that I have not accidentally left the nav lights on when I've left the boat.

I've attached a photo of the latest failed bulb, which is consistant with the previous bulbs.  I find it interesting that the glass is no longer clear, but the entire length of the bulb has a mirror like appearance, and it has a gold band at one end.  I would have expected the bulb to be like any other; clear glass with a visibly broken filament.

Any ideas?

Thanks.

[Ron Hill]

Steve : With a gold band on one end and a silver band on the other, it almost sounds like that bulb is polarized?!  Call Aqua Signal and ask them that question.  You might also want to lightly sand the points that make contact on either end to make sure they're clean.  Also make sure that you have a 12V bulb!

Try a new bulb and attach the gold end to the + positive.  Check your owners manual, but I think that the positive wire is Red for the running lights.

[Sailing Steve]

Sorry if I wasn't clear on the colorization...

It is a regular clear glass bulb from Westmarine, but it changes color as part of the failure.  All of them have been marked 12V(olts) 10W(atts) on the end of the bulb.  I'm confident that it isn't an overvoltage problem, as nothing else is suffering from pre-mature failure, including the aft nav light which is identical other than its white lens vs. red/green lens of the forward light.  The connectors are free from corrosion, and a new bulb works immediately when installed.

[Stu Jackson]

I find it hard to believe that anything on our C34s could be due to OVER voltage.  Suggest removing bulb, check voltage.  Insert new bulb, don't put cover (lens) on, check voltage, repeat as necessary, etc.  Figure out what YOUR conditions are, only way to do it.  Smells, tastes and voltages are really hard to diagnose on the Internet.  Let us know what's up.

[Ron Hill]

Steve : My first thought was overvoltage, but I dismissed that as not possible. 
Still think you need to ask Aqua Signal and see if they have any thoughts.   

[Stu Jackson]

Steve, I've thought about this some more.  Were you motoring much when this happened?  Only way I can think of over voltage is that your alternator's regulator may be putting out too many volts.  Any other problems with other lighting like interior lights?  If I read your first post correctly, it sounds like it's just the bulbs in the forward nav light.  Have you checked your voltage when the alternator's running?

[Sailing Steve]

I've never seen the light fail when it is illuminated, but then I've not had them on very often regardless.  I only discover that it has failed when I do a light check every-so-often, as I don't sail at night/poor visibility very often.

You are correct in that I'm not having any other electrical problems/bulb failures including the aft nav light which is the same bulb type.  Max voltage is 14.7, and I'm monitoring the voltage almost continually - typically 13.1 to 14.3 depending on the state of the battery charge - I use a Xantrex three stage alternator regulator.

A strange one it is.  Perhaps I'll replace it with LEDs and see if it lasts longer.  The colorization is an interesting symptom though.

[Ron Hill]

Steve : If you want to use a festoon LED you have two problem to solve first.
1. Your Aqua Signal running light fixtures are made to use a dimpled end festoon bulb - not a pointed end festoon like 99% of all festoon bulbs are!!  Don't know if there is a dimpled ended LED festoon even made?
2. You are supposed to have 225 degree lighting arc (R= 112.5 + G= 112.5) from your bow and 135 degrees from your stern light.  You won't get that many degrees out of any single LED that I know about.  However, there may be some out there? 

I sure that you can solve these problems, just wanted to make you aware of them.   

[John Langford]

I wrote a reply to Steve's point about using LEDs but it seems to have been swallowed by the ether.

I wanted to change my masthead anchor light bulb to a LED but I had two problems. First, I have Hella nav lights at deck level but didn't know if the anchor light was Hella as well. Has anyone with a 1999 MkII been to the masthead to check?

Second, the Hella manual says that the "all around light" takes a B15s bayonet bulb. I have seen B15d LED bulbs but not B15s. Does anyone know if they are close enough to substitute for each other?

[John Langford]

After posting my questions I found the following very helpful Aussie site:

http://www.ledshoponline.com/marine_faq.htm#1157chip

[jmnpe]

Hi Steve,

From what I can see in your picture of the failed bulb, you have a bad connection at the end of the bulb that ends up turning gold. It looks like a high resistance connection that is creating LOTS of heat: you are almost melting that end of the bulb.

Since the same type of bulb in the stern light is doing fine, you aren't having high voltage issues. Anyway, voltage up around 14.4 won't do that kind of damage to an incandescent bulb: a halogen, on the other hand, can overheat at those voltages and fail prematurely.

Take your bow light apart and check all parts of the connectors that hold the bulb. You probably have a loose pair of "fingers" at one end. The problem is that if it has gotten that hot, the fingers may now have lost their temper.

Happy hunting!

John