Melting AC

Hi Kevin

I purchased an old 1989 cruiser, a Regal 280 Commodore, and tripped the 20 amp dockside breaker while using a hatch a/c unit and an electric kettle. I have 30 amp service in the boat.

I reset the breaker and then the AC electric system worked for a few minutes and then went dead. Neither the dockside breaker nor onboard breaker tripped, but we smelled a burning smell. I immediately unplugged the AC system and looked behind the AC panel.

At the main breaker switch where the shore power comes in, I found the white wires melted and melting damage to the black wires. I can fix all the wires, but there is also some sort of capacitor that was wired as a jumper between the green and white wires and it is not in the wiring diagram of the boat. It looks like it has been burned out. I want to know what to replace it with, and then if this overall problem is something that points to the result of another problem or if it may have been some old wires getting warm and then touching.

I can replace everything as it was once I know what to put between the black and green wires, but don’t want to do that and then plug it in if there may be other issues that need addressing.

Thanks for your help.


The only connection in your panel between the neutral and ground would be a reverse polarity indicator. Instead of a light, some boats have an alarm. Some of the piezoelectric alarms look like capacitors.

Hope this helps


Aluminum Fuel Tank Grounding


I am told a copper ground wire should never be connected to a aluminum gas tank. Is that correct. I ask because my new tank has a ground tab welded on it.


Captain Ron

Hi Captain Ron,

Copper wire – either tinned or not tinned – is the marine standard for boat wiring.

When grounding a metal fuel tank, the main requirement is to keep the resistance between the fuel tank and the boat’s ground to one ohm or less.

Here is ABYC standard H-24 says:


Each metallic fuel tank and metal or metallic plated component of the fuel fill system, which is in contact with the fuel, shall be grounded so that its resistance to the boat’s ground is less than one ohm.”

Hope this helps,


First Trip Failure

Hi Kevin,

I recently bought a 2000 Sprint Fish and Ski.

During the first 15 minutes of taking it out the first time, the radio stopped which caused me to further investigate. None of my accessories were working at that point except the gauges. I checked the fuses and they all appeared to be good. The battery has a good charge.

I took a piece of wire and jumped it the the bilge pump switch over to the battery and it worked that way. To me it appears to be the power switch but I’m very green when it comes to boat wiring.

Please help.


Hi Ralph,

The boat engine systems are typically separate from the boat accessory systems.

If all accessories have quit, it is either the main power feed or the ground. I would check the main fuse at the battery and its connection along with the ground connection for the accessory harness.

Good luck,


Turn of the Screw


I have a 2000 Four Winns.

It has dual trumpet horns installed, one of which was not working when I bought the boat in 2005. The second horn failed last year.

My voltmeter shows 12+ volts when I press the horn button but when I hook up a new horn, nothing happens. If I direct connect the horn to the battery, it sounds. I’m confused because the voltage is there.



Hi Stephen,

This is a simple fix.

Carefully remove the sticker on the rear of the trumpet (it probably says AFI). Turn the exposed screw slowly until the horn sounds.

Hope this helps,


Ground Charge?


I need your help with a marine electrical shore power question.

My boat is plugged into dockside power and there is a 100 millivolt charge on the green ground wire. I have checked with the marina and they have checked their system which is in perfect conformity to the rules.

There is no indication of this on the shore power plug but it appears when you put a meter to the boat which is in the water and seems to make a ground through the water.

What is the reason for this?



Hi Ray,

How are you measuring the 100 mV?

Is it on the shore power plug before you connect it to your boat or is it on your boat when you compare the green to the white?



It was measured on the boat.



The 100 mV difference is simple to explain.

When current passes down neutral wire there is a slight voltage drop. Voltage = Resistance x current. Since there is no current passing down the ground wire, there is no voltage drop on it.

Your dock box is tied in with several other dock boxes with the same neutral and ground wires. If every boat was disconnected from the system, you would not see the 100 mV difference. At times, it is possible to see voltages higher than 100 mV.

Hope this helps,