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Author Topic:   Stopping Corrosion on All-round Lamp Contacts
swist posted 04-17-2014 10:09 AM ET (US)   Profile for swist   Send Email to swist  
On my 170 Montauk (and many others), the all-round lamp standard is clamped to the inside of the hull when not needed, and inserted into a rubber-cap-covered socket on the top of the console when needed.

Every Spring, the contacts on the pole and the socket come out of storage corroded. I can file them down on the pole, but the ones in the socket are way down, and it's hard to clean them. There has to be some magic goop - I've heard of dielectric grease for such applications, but then read somewhere else that dielectric grease doesn't actually conduct electricity (so what is it for?)

This must be an easy problem to solve.

Chuck Tribolet posted 04-17-2014 10:13 AM ET (US)     Profile for Chuck Tribolet  Send Email to Chuck Tribolet     
Dielectric grease does not conduct electricity, and that's
GOOD. You don't want the grease conducting electricity
between the two pins. It squeezes out of the way and you get
a good metal to metal contact at each ping.


swist posted 04-17-2014 11:20 AM ET (US)     Profile for swist  Send Email to swist     
So that means while it's not inserted it covers and protects the contacts, and then "moves out of the way" as you say.

So it is in fact the thing to use?

dfmcintyre posted 04-17-2014 12:39 PM ET (US)     Profile for dfmcintyre  Send Email to dfmcintyre     
jimh posted 04-17-2014 01:11 PM ET (US)     Profile for jimh  Send Email to jimh     
Dielectric grease is a special grease that is very non-conductive, that is, it can be used in very high voltage circuits. For 12-VDC circuits you do not need to worry too much about the conductivity of the grease. A tiny tube of dielectric grease is $5 and a quart of marine grease is $5. They are both probably okay for 12-VDC.

In general you do not apply the grease to the electrical contacts, but rather to the seals of the connector.

The theory of the grease as explained above has a big problem: if the grease is pushed out of the way when the contacts are joined, how does the grease move back into place to protect the contacts when the connector is separated? The answer: it does not. If mating the connector displaces the grease, then it remains displaced when the connector is separated, and the grease is no longer protecting the connector, which is now exposed.

The proper way to protect the connector when not joined is to use a cap or seal. Install the cap or seal over the connector. Use dielectric grease on the cap or seal to make a non-electrically-conducting seal.

For lamps on poles where the base of the pole has the connector, I suggest sealing up the pole base when not in use with some sort of cap. I bet you could find one at a hardware store in their miscellaneous rubber parts. To seal the hull-mounted mating connector, there is usually some sort of rubber flap provided. Just seal it up with dielectric grease.

If you slather grease all over the electrical contacts the only thing that occurs is a lot of dirt is attracted and held in the grease.

I have a similar installation on my boat, that is, the all-round lamp is on a big pole, and the pole is often stowed rather than kept in place. I use a Deutsch two-pole connector and have the matching caps for both connector genders. When the pole is stowed, I install the caps on the two connectors. The only dielectric grease is applied to the seals of the caps and connector bodies, never to the electrical contacts themselves. When the pole is in use, the two caps, being of different genders, actually mate with each other. I connect the two caps, and put them in a safe place, so I can find them when I stow the pole. This has worked very nicely for the last five years. There is no problem with the connections and the contacts look like new.

By the way, when I replaced the original connectors and rewired the branch circuit to the all-round lamp, the brilliance of the lamp increased significantly because it was getting more voltage than before. (The branch circuit to the lamp had four splices in it, which is just crazy--on a small boat there is no need to splice an electrical conductor, as none is going to be very long.) The light output of an incandescent lightbulb varies exponentially with applied voltage (to the 3.4-power), so even a modest increase in voltage results in a noticeable increase in light output.

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