Bow/Anchor Light Problem - NEED HELP

98proline

Recruit
Joined
Apr 1, 2010
Messages
3
I have a 3 position switch. Center is off, up is nav lights, and down is anchor light. Anchor light works, but when flipped up, only bow works. I disconnected everything to try and figure out what's going on and this is the wierdest problem. I left the ground hooked up. I flipped the switch up, and hooked up the anchor light. It works. I unhooked it and then plugged in the bow light to the same prong. It works. I tied the two together and plugged it into the prong and only the bow works. I then untied them, plugged in the anchor light and it works. I used a piece of wire and connected bow lights to same prong and anchor lights go out. Why won't both of these positives work together? I even tried it on my bilge switch. I unhooked the positive to it and plugged in the anchor. It worked. As soon as I touch the bow to it, the anchor went out and bow is on. I even tried the following: left anchor hooked up to nav prong and plugged bow into the bilge prong. When I flip the bilge prong, the bow would come on, yet the anchor would go off. If I unplugged the bow, the anchor comes back on. Any suggestions????
 

diesel5599

Petty Officer 2nd Class
Joined
Sep 4, 2006
Messages
169
Re: Bow/Anchor Light Problem - NEED HELP

How much you want to bet its a ground problem? 99% of the time its a ground problem. Sure both work alone, but what is happening is you need more current (amperage) to power two 12v loads vs one.

So lets say you have a dirty but workable ground. You plug in the first 12v load. The completed circuit is probably only about 11.4 or 11.5v due to the dirty ground. This is still sufficient to power the first load because 12v bulbs are a bit tolerant and will probably light at input voltages between 11-14v.

But lets say you plug in the second 12v load. Now due to your dirty ground only 11.4v is getting through which is a 0.6v drop from what it should be to begin with. Well now you are asking for even more current and the completed circuit needs more amperage. So what will happen is the load that needs the least amperage, in this case the bow light, will win. The stern light will not light since the dirty ground is providing too much resistance for sufficient amperage to get through. Typically both lights will not work in this scenario but its still possible for only one to light.

So, clean your ground and you'll be good to go. A little dielectric grease will go a long way.
 

98proline

Recruit
Joined
Apr 1, 2010
Messages
3
Re: Bow/Anchor Light Problem - NEED HELP

Thanks! I will try working on it tomorrow and post the results.
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,762
Re: Bow/Anchor Light Problem - NEED HELP

Do you understand that in the NAV position BOTH lights are supposed to be on and in the ANC ONLY the anchor light is on? Next we need to know what kind of switch you have. 1) does it have an indicator light in the switch? If not, there is no ground on the switch. If there is, the ground has nothing to do with the lights -- it is simply a ground for the indicator light in the switch. 2) Does the switch have 3 or six terminals? If it has three terminals, the switch MUST have a diode to make it work properly. Diagram is shown below.

Nav-AnchorSwitch.jpg


If the switch has six terminals the lights are wired like this.
NavSwitchWiring.jpg


If the switch has a light in it that part of the switch looks like this:

LightedSwitchWiring.jpg
 
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