voltage drop with deck light only

[chelsabella]

Just rewired my mast with new wire for anchor light and combo deck/steaming light. Testing connections with 12v battery prior to stepping the mast and all lights worked. Stepped mast and now anchor light and steaming light work fine (LED), however when I switch on deck light volt drops at least one volt and am/fm radio loses power. Radio is not wired to mast wiring at all. Of course the quick connect is in the mast. Quick connect was tested prior to stepping mast and all read proper voltage. Suggestions

 

[Don S/V ILLusion]

As I suspect you also suspect the connection. Quick connects are infamous failure points— yours sounds like a high resistance typical symptom

 

[Captain Larry-DH]

Put a clamp-on ammeter on the wire to determine its current draw. The voltage drop elsewhere could be the result of a short and very high current draw. If so, there should be a hot wire and your breaker or fuse should have blown. suspicious. If there is a breaker malfunction or other mis-wired ‘odd‘ situation it might be a fire hazard.
Edit - if your boat has an amp meter at the main electrical panel it should show a high load, if it exists.

 

[Davidasailor26]

Where are you measuring the voltage to see a drop? A voltage drop only affects points between the drop and the load. If there’s something wrong in the mast causing drop you wouldn’t see that reflected in the voltage at the main panel.

I guess it’s possible the light’s ground is shorted to the mast and using that as its return path, with a bad connection to the proper ground along the way. Something odd going on though.

 

[chelsabella]

Where are you measuring the voltage to see a drop? A voltage drop only affects points between the drop and the load. If there’s something wrong in the mast causing drop you wouldn’t see that reflected in the voltage at the main panel.

I guess it’s possible the light’s ground is shorted to the mast and using that as its return path, with a bad connection to the proper ground along the way. Something odd going on though.

The drop is at my volt meter which is on the switch panel wired to the Guest switch. I only get the drop when the deck light is switched on. everything else works fine

 

[chelsabella]

Where are you measuring the voltage to see a drop? A voltage drop only affects points between the drop and the load. If there’s something wrong in the mast causing drop you wouldn’t see that reflected in the voltage at the main panel.

I guess it’s possible the light’s ground is shorted to the mast and using that as its return path, with a bad connection to the proper ground along the way. Something odd going on though.

The anchor and steaming lights all use the same ground and they work fine

 

[chelsabella]

As I suspect you also suspect the connection. Quick connects are infamous failure points— yours sounds like a high resistance typical symptom

The quick connect is new and was pre wired by Catalina Direct I only had to attach the female end at the mast step

 

[Davidasailor26]

The drop is at my volt meter which is on the switch panel wired to the Guest switch. I only get the drop when the deck light is switched on. everything else works fine

Put a clamp-on ammeter on the wire to determine its current draw. The voltage drop elsewhere could be the result of a short and very high current draw. If so, there should be a hot wire and your breaker or fuse should have blown. suspicious. If there is a breaker malfunction or other mis-wired ‘odd‘ situation it might be a fire hazard.
Edit - if your boat has an amp meter at the main electrical panel it should show a high load, if it exists.

I’m with Larry - If you’re seeing a 1 V drop at the main panel from the deck light it’s drawing way more than it should. Find a way to check the amperage draw to confirm that’s the case, then try to track down (1) where the partial short is that’s causing the big draw; and (2) why that hasn’t tripped some overcurrent protection.

 

[Don S/V ILLusion]

The quick connect is new and was pre wired by Catalina Direct I only had to attach the female end at the mast step

Irrelevant. You have a high resistance somewhere and my guess is a connector. it’s now buried in the mast, start by looking at any other connections to eliminate the easy access ones.

 

[Davidasailor26]

Irrelevant. You have a high resistance somewhere and my guess is a connector. it’s now buried in the mast, start by looking at any other connections to eliminate the easy access ones.

A high resistance connection wouldn’t lead to voltage drop at the panel - it would just reduce the voltage available at the light. From the panel’s perspective it would just be like having a higher resistance (lower wattage) bulb at the end of the circuit.

 

[LloydB]

Just off hand looks like a ground fault. So if you begin checking for that you will probably find out the cause if it is not.

 

[thinwater]

You more likely have a battery or a battery wire problem. If the lights were pulling enough amps to drop the voltage at the meter, a breaker would pop. 15 A is nothing for a good bank. But a restriction at the battery or a bad battery will cause the V to drop rather easily. The LEDs don't pull beans but the deck light does.

Spring commissioning brings out many faults. Just because you re-stepped the mast does not mean that is the cause of the problem.