In the process of installing new batteries on Still Crazy this weekend, I encountered several curious problems. As I connected the final negative ground across the battery banks, I saw a spark as the lug touched the terminal. Problem was that the battery selector switch (1, 2, Both, Off) was set to OFF and the battery was otherwise not connected to anything (including the sump pump or the battery charger). I checked the selector switch and in the OFF position there was no continuity between the common terminal and terminals 1 and 2. I disconnected the batteries entirely and as I investigated further I found that four circuits (cabin lights, macerator, steaming light, and running lights) showed continuity from the positive bus to the terminals on the other side of their breakers even though the breakers were in the OFF position! In addition, when I disconnected these four terminals from their breakers, each one showed continuity with each other! Could all 4 be shorted out shorted out together somewhere? I was using a simple bulb type continuity tester. I had recently installed a fan in the V birth on the cabin lights circuit so I disconnected it to see what would happen. I still detected continuity across the 4 closed breakers but perhaps the light was not quite as bright. Finally, I reconnected one battery, again with the selector switch on OFF. Again I saw a definite spark as I connected the negative terminal but it was much fainter. I inserted my multimeter between the battery terminal and the ground (negative) lug and it read only 0.01 milliamps; then same as when it is connected to nothing. Not only can’t I figure out what is going on, I can’t even think of what to test next. All my buddies at the dock are also stumped. Any thought would be greatly appreciated.
Wireing Quagmire
- Thread starter Jeff652
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First get a accurate mulitmeter. Not sure how your measuring current without one used properly?
If your alternator is in fact wired direct to the battery, the diodes will draw, might just re-verify that is not the case.
As far as the breaker behavior... even when you disconnect the breakers from the +12 bar you are still completing the circuit to ground thru the devices themselves, for they are generally low resistance devices. So current flows from the first breaker thru the device to ground then from ground thru the second device and back to the other breaker. Tricky tricky, remember the grounds are all tied together...must get a real multimeter and then you would have seen it was not dead complete short.
If your alternator is in fact wired direct to the battery, the diodes will draw, might just re-verify that is not the case.
As far as the breaker behavior... even when you disconnect the breakers from the +12 bar you are still completing the circuit to ground thru the devices themselves, for they are generally low resistance devices. So current flows from the first breaker thru the device to ground then from ground thru the second device and back to the other breaker. Tricky tricky, remember the grounds are all tied together...must get a real multimeter and then you would have seen it was not dead complete short.
Thanks for your help. It took me a few hours to think about it but now I see how the current will flow through various devices via the ground bus. As far as the spark that I saw when I hooked up the circuit, the spark went away when I disconnected all the bilge pump wires on the panel breakers. Apparently even though the battery selector switch is set to OFF, and the bilge pump will not operate, current gets to the sensor of the float switch. So problem solved (actually there never was a problem)
Bilge pump should be wired direct and still operate with the selector in the off position. There is also a Manual, Off, Auto switch on the panel, keep it in auto. Not sure what type of float switch you have, but it would seem by it self that it should not be drawing any current.
You know, you're right. I was a little too accepting of this explanation. I'll have to look at it a little further whern I get down to the boat next week.
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