Help with a non working runing light

seamyst · #1 (**permalink**) 12-02-2007

My Starboard running light will not work. It has power at back of fixture and also at the point where base of bulb touches the two contact points??????
I changed bulb with Port and both work there, I NEED HELP. Trying to head South as soon a light is working.

Any ideas???

TrueBlue · #2 (**permalink**) 12-02-2007

If you read 12v at the fixture base and the bulb is still good, one cause could be corrosion on the metal surface in contact with the bulb's ground. A faulty ground is common on boats.

Try cleaning all metal contact surfaces with emery cloth or fine sandpaper and then spray with CRC electrical contact spray, or it's equivilent.

seamyst · #3 (**permalink**) 12-02-2007

There is no sign of corrosion on fixture, it was changed out last year. Contacts are one Positive and the other negative. Fixture does not ground at mount. It is a Aqua signal mounting on bow sprit rail.I'll try spraying ,anything to get working. This makes no sense to me, why the bulb will not light

TrueBlue · #4 (**permalink**) 12-02-2007

Strange. Perhaps a faulty switch? But I suppose that would cut out power at the lamp base.

seamyst · #5 (**permalink**) 12-02-2007

no, both Port and Stern are working

TrueBlue · #6 (**permalink**) 12-02-2007

Does polarity make a difference - such as right hand vs left hand rotation, or does the bulb only lock in one direction?

Rockter · #7 (**permalink**) 12-02-2007

seam...
Often, if you have corrosion anywhere in the line, you can detect (say) 12 V at the terminals, but the moment you try to draw a load, the corrosion chokes off the current.
Take another bulb out to the light fitting, and you will probably see that the bulb will not light either.
Sounds like corrosion... this is a classic symptom I noticed.

seamyst · #8 (**permalink**) 12-02-2007

I've tried reversing wires still no luck.
Maybe corrosion down line? In the morning I'll try running a long jumper wire and see what happens.

rhaley · #9 (**permalink**) 12-02-2007

To test Rockter's theory (which appears to be very probable with the info you have given), put a known good bulb in the fixture and measure the voltage across the bulb. If it is 12V without the bulb, and much less with the bulb in place, you have a poor connection that is failing under load.

seamyst · #10 (**permalink**) 12-02-2007

How do you measure across the bulb?
I know the bulb works I took it from Port light and was burning at time