Bow Nav Lights Keep Blowing

[JohnTN]

The port and starboard nav lights on my pontoon boat keep blowing after a couple of outings, usually one or the other, not both. I have replaced the starboard bulb 3 times and the port 2 times. The bulbs are the standard 8 watt (CP10) I think.

Any suggestions?

John

 

[fdmsiv]

Re: Bow Nav Lights Keep Blowing

Two major enemies of light bulbs, corrosion and shorts.

Make sure your wiring isn't shorting out. Sounds like it would be in the return run from the light to the battery.

Check the sockets for corrosion. Clean up the contacts. Usually corrosion stop electricity flow, but it has been know to do a funny thing or two sometimes.

 

[JohnTN]

Re: Bow Nav Lights Keep Blowing

Correction, the bulbs are 10W, .8A, festoon style. I measure voltage of 11.8V at the socket with the engine not running.

 

[JohnTN]

Re: Bow Nav Lights Keep Blowing

fdmsiv,

By return line do you mean the return to ground?

The boat is only 14 months old, but the first bulb blew last year within a couple of months of getting the boat. The contacts are clean.

I disconnected the positive and ground wires from the light and measured the resistance across the two wires with the switch in the off position. I measured a resistance of 1.5 (on 200 scale). Shouldn't it be infinite with the switch in off position?

John

 

[Silvertip]

Re: Bow Nav Lights Keep Blowing

Shorts don't blow bulbs. Shorts blow fuses. Shock, vibration, high voltage, and cold water on a hot bulb blow the bulbs (which is why one disconnects the trailer lights before backing in the water). Did you actually measure the resistance of the bulbs to make sure they were bad. Simply replacing a bulb in a socket that's loose may make the new bulb work for awhile, but appear to blow when its just the socket that loosens up. This is a new boat so overvoltage should not be a problem as the charging system is well regulated. That should not stop you from measuring system voltage with the engine running at 1500 - 2000 rpm. If its over 15 volts that may be the cause.

 

[haskindm]

Re: Bow Nav Lights Keep Blowing

If possible, find one of the new LED bulbs that will replace the existing bulbs on your boat. They give off very little heat, consume less power, and are much more immune to vibration. They are pricey but should last for years.

 

[JohnTN]

Re: Bow Nav Lights Keep Blowing

I believe there is a good chance that water is contacting the male spades on the bottom of the light.

The lights are mounted on the flat surface of the plywood deck above a 1 inch hole in the deck for the wires to come up from underneath. The spades on the bottom of light housing protrude down into the hole about a quarter inch. So in rough water or when the boat is heavily loaded (10 people on board) the water from the front of the pontoon could be splashing up into the 1 inch hole and wetting the negative and positive spades.

Seems like this would cause a short, not a blown bulb, though. And by blown, I mean the glass is cracked and the inside of the bulb is fogged or burnt. Kind of like it got hit by cold water when hot. But the bulb is well sealed in the mount and no sign of water inside the housing.

I will try sealing the wire hole from underneath and see if that solves the problem.

 

[fdmsiv]

Re: Bow Nav Lights Keep Blowing

I had a similar problem, back before I knew anything.. I wired some lights on a trailer with a separate battery so I could see around the trailer at night. The negative wire from the light was damaged and a bit of the insulation came off. The wiring wasn't the best and I was too dumb to not include a breaker or fuse. Long story short I would turn on the lights and start messing in and around the trailer. There would be a pop and the lights would go out. The bulb was acting like a fuse, the wire was shorting and the bulb was taking what the wiring was passing through.

I now know that fuses blow before bulbs, but if you bulb is your fuse you will have a similar experience.

Water on a hot bulb will also do the trick. How long are your lights on before they go, are they going out only on the water or at some other time?

 

[bruceb58]

Re: Bow Nav Lights Keep Blowing

The bulb was acting like a fuse, the wire was shorting and the bulb was taking what the wiring was passing through.

You wire a bulb directly across a battery. How much shorter of a circuit can you get. It is impossible to blow out a bulb with a short circuit since the bulb basically requires a short circuit to even operate.

 

[Boatist]

Re: Bow Nav Lights Keep Blowing

If the glass is cracked I bet the water gets to the glass on the blub. This is very normal on trailer light that are not water proff.

Try putting some plastic or something to prevent water from hitting the blub or go to the LED lights. I would also check the lamps voltage with the engine running at crusing speed. Some motor do not have regulators but then on the other hand it usually cause the filliment to burn out not the blub to crack. Cracked bulbs has always been water contact in my experience.

 

[Silvertip]

Re: Bow Nav Lights Keep Blowing

Cheaply constructed lights on a boat tend to collect condensation on the inside of the fixture. The all around light on the bimini of my pontoon was just such a fixture. Always had moisture in it. The solution was simple and cheap. A little grease on the threads of the lens sealed the fixture. No more condensation.

 

[JohnTN]

Re: Bow Nav Lights Keep Blowing

You are right about water contact blowing the bulbs. Upon closer inspection, the two tabs for the wire hook up protrude thru the base of the housing and this hole is open into the cavity that the bulb is in. So, splashling water or waves that hit the bottom of the deck could introduce water to the hot bulbs.

Sealed the opening with rubber gasket with slits for the wire connectors, expect the problem is now fixed.

Thanks,

John

 

[hard-3]

Re: Bow Nav Lights Keep Blowing

go to the auto parts store and get a tube of di-electric grease and coat the base of the bulbs this will help prevent corrosion and will displace water form getting to the sockets also helps with vibrations