Running Light Problems

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Jun 1, 2009
17
Hunter 34 Croton on Hudson, NY
For the last few weeks, my running lights would only stay on when the engine was running. Otherwise they trip the circuit breaker instantly or within a minute or two. Last night the problem evolved to where they only stay on when the engine is running and in gear (I assume because it's revving at a higher rate). Any ideas for how to diagnose the underlying problem?
 
Mar 6, 2008
1,375
Catalina 1999 C36 MKII #1787 Coyote Point Marina, CA.
Seems that the house batteries need to be replaced.
 
Jan 12, 2011
930
Hunter 410 full time cruiser
Does the running light wiring run though/next to any part of the engine?

The only thing I can think of is that there is a wire short to the engine and when it runs the wire moves some. If the breaker has been tripping there has to be a short in the circuit somewhere.
 
Oct 14, 2005
2,191
1983 Hunter H34 North East, MD
Re: Running Light Problems ...

Interesting that they only stay on with the engine running but short out otherwise. Check the wiring where it enters or leaves the bow or stern railings to see if it has rubbed through and shorting out where the positive could touch a grounded part.
 
May 13, 2011
420
Hunter 40.5 Legend Jupiter
Interesting that they only stay on with the engine running but short out otherwise. Check the wiring where it enters or leaves the bow or stern railings to see if it has rubbed through and shorting out where the positive could touch a grounded part.
I would go with Dan's suggestion first - I had a similar issue and after fault finding to the point of having to physically cut the cable of each light - re-wire and then cut the next one I found out it was a faulty starboard nav light causing the problem.

I had no wire failure that could be spotted and as these were sealed units it was the only way I could do it - plus I was underway in the middle of the night when it happened!

I believe although not 100% sure that some water had got into the 'sealed' light and was causing it to short (or it had just developed a fault after 12 years...) - although its not an ideal practice, I did find it after about 5 minutes of cutting, re-crimping, cutting, re-crimping. Once it was removed from the circuit there was no tripping and since replacing it I've never had a problem.
 
Jun 1, 2009
17
Hunter 34 Croton on Hudson, NY
So. Occam's Razor strikes again. The compass light is wired to the running light circuit and the wire for it runs right up by the transmission. The fixture is attached to the16 gauge by exposed metal connectors which were touching and causing the short. Shifting into gear must have just moved the wires around enough to avoid the short. Replaced the metal connectors with plastic caps and voila. No short.
 
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