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Posted: Tue Jun 21, 2011 1:19pm

Post Subject: 12v electrical glitch.

I have recently in the last 4 months purchased a 50ft well maintained narrowboat.It has performed brilliantly over the past few cruises. However last weekend prior to leaving on a weekend cruise I discovered there was no 12v power to the 12v fridge and neither to the 12v stereo cd system which is a fitted car stereo. And the fridge and music players connections are visually secure. Both are fitted to the starboard side of the boat. All the other 12v systems including lights and 12v sockets are fine with power still supplied. I also have a 240 inverter which is working fine supplying power to other items when needed. There doesn't seem to be any blown fuses on inspecting the fuse board but I will return to this when I go back to the boat with a circuit tester. But I was wondering if I should inspect anything else. I have recently also replaced my shore power line with a newer one and that feeds to the battery charger and was also wondering if that has influenced the problem. Many Thanks... Ian Wilson


Posted: Tue Jun 21, 2011 5:54pm

Post Subject: 12v electrical glitch.

The fridge should be wired direct from the switched side of the domestic master switch and it should have a fuse close to that connection - NOT in the main fuse board. This minimises the length of unprotected cable. So it may yet be a fuse that you have not discovered. Likewise a car radio with memory circuit is allowed to have ts memory cable connected directly to the battery side of the master switch or straight onto the batteries, again with a fuse close to the connection. If you have been delving about near the batteries and master switches my guess would be broken connection. After that I agree a fuse is the most likely but a 12v fridge should not really share it's fuse with a radio although as long as the radio cable has a larger current capacity than the fridge fuse I suppose it is electrically safe. The its trace the wires and look for a break, remembering the negative as well. The reason the fridge is wired straight from the master switch (although I know many boats where this is not done) is because it demands an exceptionally high starting current so it needs apparently ridiculously thick cables running from as close to the battery as possible. Doing anything with a mains circuit should have no effect on a 12v one because they must be at least 30mm apart or separated with a physical barrier. Tony Brooks

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