Navigation light issues

[JERRY Myers]

New to the site and have a boat navigation question. I have checked the switch with my multi meter and it works properly With the lights unplugged I have 12 volts at the wires. When I plug the lights in they don't illuminate and power drops to zero volts. Any idea on how to fix this or where to look. I tried a different switch wired to turn them on and no go. 1992 Starcraft Superfisherman190

 

[Texasmark]

which light, bow and stern, one or the other? Boat connector could have crud in it, shorting things out. Light bulb socket could be contaminated...metallic material smudged over the contacts.. pull the bulbs and ohm wires to each other and wires to case of light pipe...should be infinity with bulb out.

 

[JERRY Myers]

Both I can take the socket out of the boat where they plug in and hook the wires to a battery and they work fine. So they do work properly. Switch is wired properly with the diode too. There is another light where the trolling motor mounts on the bow using the same ground and works just fine. I remember correctly I get about 1 to 3 ohms. It has the old 3 pole switch if that matters.

 

[dingbat]

You either have the positive wire shorted to ground somewhere in the circuit somewhere between the switch and the lights or.... you have a bad connection or wire between the switch and it’s power source.

Pull the wires from the switch and remove any light bulbs in the circuit. Check for continuity across the wires you pull from the switch.

With the lights on, check the voltage at power source suppling the switch

 

[gm280]

Have you actually checked the bulbs themselves? If the bulbs, either of them, is shorted, that will keep them from working and depending which bulb it is, both front and rear would be effected. If you are anchored, then only the rear light should be on. But if navigating both lights are supposed to be on. And if the rear is shorted, it would keep both from coming on. JMHO

 

[JERRY Myers]

Center lug on the switch has 12 volts to it. Could be shorted wire but doesn't make sense to me being that the wire has voltage at the terminals that the poles slide into until until the pole is inserted. Might replace the power tire end and clean the terminals with emery cloth to make sure it's not just a lack of current flow.

 

[JERRY Myers]

Yes anchor bulb was burnt out and replaced with new. Both lights work fine when hooked up to another battery. I've read some of the older post about issues and have tried all that was suggested. I even printed the diagram and made sure everything was wired correctly.

 

[JERRY Myers]

I work with electronics for a living and have tried all I could think of. I even pull the diode off one side of the wire and still neither light will work even separately. As I said when the light is put in the circuit the voltage drops to zero volts that's what has me baffled because you still should measure 12 volts on the wires even when the light is lit correct?

 

[dingbat]

As I said when the light is put in the circuit the voltage drops to zero volts that's what has me baffled

Ohm’s law

Electronics 101...
Rule #1: confirm your power source and work forward.

 

[dingbat]

[No message]

 

[froggy1150]

Get a test light, not led, not low current but something with a significant draw and follow the circuit. A meter will tell voltage but won't test current flow

 

[gm280]

With what you stated, there wasn't much more that could have been the problem other then one or the other bulb.

Here is my diagram for wiring such lights for an easy pictorial diagram.

 

[Texasmark]

Mentally running through this: A 5 watt bulb (assumed) at 12v would be a hot resistance of 2.4 ohms with 5 amps flowing; less when cold. For there to be 0V on a DMM with the lowest scale of 20v and 2 decimal places, you'd have to have 2k of resistance or so somewhere in the circuit (quick mental calculation). 2k could easily be a corroded terminal.

 

[mike_i]

Just to clear things up are you saying that you're measuring 12v at the switch but it drops to zero when you turn the switch on? If that's the case you probably have a short in that ckt. Are the wires getting hot or fuses blowing? Sounds like when you flip the switch your connecting the 12v line to a short to ground which would lower the voltage to zero in reference to ground.Are these regular light or LED's?

 

[tpenfield]

Mentally running through this: A 5 watt bulb (assumed) at 12v would be a hot resistance of 2.4 ohms with 5 amps flowing; less when cold. For there to be 0V on a DMM with the lowest scale of 20v and 2 decimal places, you'd have to have 2k of resistance or so somewhere in the circuit (quick mental calculation). 2k could easily be a corroded terminal.

I get 28 ohms and 416 milliamps

 

[76SeaRay]

Were these working and suddenly quit or has something been changed? Something to consider; the problem may be upstream on your 12 volt pin on the battery side. High resistance somewhere in that lead could cause voltage drop to the switch leaving nothing to feed the lights.

If these are LED lights, you could have one or both wired backwards. Reverse polarity wouldn't blow a fuse, they just wouldn't turn on.

 

[Texasmark]

I get 28 ohms and 416 milliamps

2k number was a SWAG considering his zero volt reading on a 20.00 DMM scale...