Earlier this year I was talking to a person who said he had endless trouble with electric pumps in kayaks and had stopped using them. This surprised me as I have been using them for over 25 years with very little trouble. I may not be doing as much kayaking now as I used to, but once I was out every weekend. The electric pump worked reliably year after year. But making a submersible electrical system is difficult and needs to be installed with a great deal of attention to detail.
The problem over the years would be
1. The switch would start to get intermittent, and eventually fail. I guess on average I would replace the switch every 3 or 4 years.
2. Over a longer period the copper wires would eventually corrode inside the plastic, and the whole lot would need to be replaced. Maybe 6 or 7 years.
3. The positive battery terminal would get weak and spongy and break off. This is easily fixed by digging into the plastic and soldering a wire on it.
I recently had to replace a switch on my trusty Sea Leopard, and took the opportunity to dismantle the switch to see why it was playing up. I always imagined that eventually water was getting into it to stop it working. This was only part of the trouble.
Quite obviously water has got in through the rubber housing.
The water has got in through the rubber housing, through two holes.
two holes on one side of the main body go right through, don't ask me
So when installing this switch, these little holes need a bit of silicon in them to seal them.
But there is not much sign of water inside the switch.
But the left hand contact has pitted where the moving contact (below) hits it.
The bottom contact should be a nice smooth dome, but has worn flat on the tip.
So water didn't seem to be the main problem - the pitting was. I don't wish to get into too much technical detail, but switches designed for use with 240V AC (or 110V AC) are not well suited to low voltage applications - like 12V DC. Low voltage usually implies heavy currents - several amps - whereas 240V AC lights, TVs etc are under 1 amp. So when a switch switches a heavy current it produces a spark, and this spark eventually pits (burns away) the metal contacts. This can be reduced or eliminated by using a spark quench. This is a capacitor, or resistor and capacitor connected across the switch contacts. So the new switch I have installed has a spark quench (330 ohm resistor and .01 mf capacitor in series) soldered across the wires.
Make sure you slide heat shrink plastic over the wires first.
Cover it all with epoxy glue.
Slide the heat shrink over everything and heat it.
Of course it will be a few years if I know whether this switch lasts longer than previous ones.
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