triplec Posted July 17, 2021 Report Share Posted July 17, 2021 Alright electrical gurus....I have read some of your re-wire posts in our group here and have a question. I am helping a buddy on his 2016 Cobia 296. His incandescent bow light is out and checked all the usual...bulbs, volts at light etc.. I thought it was the switch but when bypassing the switch at panel the light still didn't work. I cut the light and removed the light and jumped it to battery direct and it works fine. I have 12 plus volts and what seems like a good ground at the connection to light in the bow. Well its reads on my basic meter anyway. However, when I attach the wires from light to lead from panel the volts drop to 3 volts and light doesn't work. So...does that indicate a bad ground you think? I thought bad light fixture but I can run the light off my 6 volt trickle charger that I used as a tester to check light fixture so it seems to only need a few volts as I set it to 6 and it works dimly but on 12 it is solid and bright. What I thought was simple switch change is a tad confusing now. 🤪 The volt drop throws me off as if shorted it seems like it would blow a fuse and if light base was shorted I wouldn't be able to make the light work wiring direct...or so I think. Everything else even electronics seem to be running ok. I know they are volt sensitive so I sort of assumed the panel ground was good....I know I know...😩 The plus side is there is excellent access to the back of the switch panel...Im just not sure what all needs testing and why it shows up good on my meter until I connect a light device...yet the light device seems good. Or at least the bow one. The anchor light when it was on seems dim but I thought it would be wired direct to switch and I have it unhooked and havent chased it down yet thinking the bow light was wired separately. Thanks for any thoughts you have time to share that I can pass on to him. Quote Link to comment Share on other sites More sharing options...
jh141 Posted July 18, 2021 Report Share Posted July 18, 2021 How did you bypass the switch? Is the switch the most common used double throw so you can run the anchor light without the navigation lights? The voltage drop indicates a load problem. Bad wire or switch. You can measure 12 volts dc and not have enough current (amps) to drive a device. In reality a light is a short across the filament. Keeping in mind most boats have the Anchor light and Navigation light wired to the same switch, using the same source with the ability to turn off the Navigation light if that helps and makes sense. Quote Link to comment Share on other sites More sharing options...
jh141 Posted July 18, 2021 Report Share Posted July 18, 2021 Quote Link to comment Share on other sites More sharing options...
Headhunter Posted July 18, 2021 Report Share Posted July 18, 2021 Todd, had that type of issue on my gps. All of JH’s thoughts are correct. I found my issue at the switch panel as a poor power connection at the switch next to the one that controlled the gps. I am not sure I am clear but it was the power wire that goes loopy,loopy to power all of the panel switches. Good luck! Quote Link to comment Share on other sites More sharing options...
RacerxV6 Posted July 18, 2021 Report Share Posted July 18, 2021 also, don't forget the breaker for that switch. I had a similar issue with my live well. no power, it was the breaker so if you disconnect it from that breaker that is for that switch and move it to one over and test it. the switch may be fine but the breaker is bad. just my experience. 1 Quote Link to comment Share on other sites More sharing options...
triplec Posted July 18, 2021 Author Report Share Posted July 18, 2021 19 hours ago, jh141 said: How did you bypass the switch? Is the switch the most common used double throw so you can run the anchor light without the navigation lights? The voltage drop indicates a load problem. Bad wire or switch. You can measure 12 volts dc and not have enough current (amps) to drive a device. In reality a light is a short across the filament. Keeping in mind most boats have the Anchor light and Navigation light wired to the same switch, using the same source with the ability to turn off the Navigation light if that helps and makes sense. I bypassed the switch by making a jumper that would let me connect the bow nav light to the hot wire supplying the nav light switch. I thought probably the switch was bad as it seemed to have some play. I still had nothing at the light so I cut the light leads at the connector to the light in the anchor locker thinking maybe connecter bad. Tested light by direct conn to battery with some more jumpers I use with clips. I tested the wires going to bow thinking bad ground and made a new ground wire test run and laid it on the deck. I later used it to test hot when I had current. Volts read well over 12 both tests w meter but wont run the light. I read elsewhere that means less than 4 volts for incandescent. What I didn't do was test on another switch as Chuck mention below as I didn't think the loop de loop if you will....would be bad. Now I think it may be further back as I merely checked break but didnt swap them. Thats the next task I think. Further info learned today was that he has other lights specifically his underwater LEDs that havent worked in a bit. I am suspicious its all related now and may be a bigger connection either ground or hot. Thanks for the diagram I Amy need that upon switch reinstall. I havent schooled up on how to test the switch itself yet too. 1 Quote Link to comment Share on other sites More sharing options...
triplec Posted July 18, 2021 Author Report Share Posted July 18, 2021 7 hours ago, Headhunter said: Todd, had that type of issue on my gps. All of JH’s thoughts are correct. I found my issue at the switch panel as a poor power connection at the switch next to the one that controlled the gps. I am not sure I am clear but it was the power wire that goes loopy,loopy to power all of the panel switches. Good luck! That makes sense and I didn't think to check another circuit! I could not make the light work jumping off the hot and ground at the back of the switch panel only last trip over so that could be it. Keep the ideas coming Chuck! Quote Link to comment Share on other sites More sharing options...
triplec Posted July 18, 2021 Author Report Share Posted July 18, 2021 3 hours ago, RacerxV6 said: also, don't forget the breaker for that switch. I had a similar issue with my live well. no power, it was the breaker so if you disconnect it from that breaker that is for that switch and move it to one over and test it. the switch may be fine but the breaker is bad. just my experience. Thank you! I did check the breaker to make sure it wasn't tripped but I don't have those on my boat so terribly unfamiliar with how they work. I have a buss bar and fuse block setup so that didn't cross my mind. We will pull the panel and have a look at that next time I am over at his place! Quote Link to comment Share on other sites More sharing options...
HoneyB Posted July 18, 2021 Report Share Posted July 18, 2021 Dumb down the trouble shooting. Go buy a simple 12 volt test light. Grab some wire that will reach from the light to the negative battery post. Turn the light switch on and run the wire as a ground all the way to the battery. Clamp the test light to the ground and touch the light wiring. It the light come on you likely have a bad ground. If no light in the test light then likely power side is the issue. Simply back up to the switch with the test light. Test the switch for power in and out with the trusty test light. 1 Quote Link to comment Share on other sites More sharing options...
RacerxV6 Posted July 18, 2021 Report Share Posted July 18, 2021 2 hours ago, triplec said: Thank you! I did check the breaker to make sure it wasn't tripped but I don't have those on my boat so terribly unfamiliar with how they work. I have a buss bar and fuse block setup so that didn't cross my mind. We will pull the panel and have a look at that next time I am over at his place! Breaker doesn't necessarily need to be tripped. It could be out right bad. But like Honey B states dumb it down....you'll figure it out!!! 1 Quote Link to comment Share on other sites More sharing options...
triplec Posted July 23, 2021 Author Report Share Posted July 23, 2021 On 7/18/2021 at 12:31 PM, RacerxV6 said: ...don't forget the breaker... And...breaker it was! It was bad and not flowing the load. Bypassed that sucker and everything came alive! 3 Quote Link to comment Share on other sites More sharing options...
RacerxV6 Posted July 25, 2021 Report Share Posted July 25, 2021 Glad I had some advice that someone could use...I often use so much advice from others on this site it is nice to have helped a fellow angler..... 2 Quote Link to comment Share on other sites More sharing options...
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