Electrical fault?

[Seashoreman]

I am trying to figure out what could be causing this problem. I have a new 100a battery and a good 70a, they start the engine OK and the meter shows they are both healthy. However, I can have one item on, such as depth sounder, radio, lights, etc and when I turn something else on the whole lot goes dead? After about 10 mins I can get one thing to come on again without touching anything.
Checked fuses, no problems, checked most of wiring, no loose wires. Driving me nuts! All I can suppose is that I may have got water into one of the two isolator switches (ones with red removable toggles) when I recently wiped out locker with damp rag? Do I replace these switches? Everything worked fine until I did this. Have tried wd40 on them.
Boat on a swinging mooring so need to get out to it to test things. Any ideas?

 

[Talulah]

I am trying to figure out what could be causing this problem. I have a new 100a battery and a good 70a, they start the engine OK and the meter shows they are both healthy. However, I can have one item on, such as depth sounder, radio, lights, etc and when I turn something else on the whole lot goes dead? After about 10 mins I can get one thing to come on again without touching anything.
Checked fuses, no problems, checked most of wiring, no loose wires. Driving me nuts! All I can suppose is that I may have got water into one of the two isolator switches (ones with red removable toggles) when I recently wiped out locker with damp rag? Do I replace these switches? Everything worked fine until I did this. Have tried wd40 on them.
Boat on a swinging mooring so need to get out to it to test things. Any ideas?

Water in the isolation switches wouldn't make any difference unless you now had corrosion across the contacts.
I had a similar problem and only identified the issue when I actually disconnected cables/wiggled cables instead of just looking at them.
The fact the engine starts ok suggests the engine start circuit is ok so I would be looking at both the positive and negative connections to the main panel.
Take a pair of jump leads and connect these direct from the battery to the panel and then see if you still have a problem. You can then move jump leads around cutting out parts of the system. You could put jump leads either side of your toggle switches.
I'm sure others will be along shortly with similar stories.
Remember though the problem could be negative related as much as positive related.

 

[halcyon]

I am trying to figure out what could be causing this problem. I have a new 100a battery and a good 70a, they start the engine OK and the meter shows they are both healthy. However, I can have one item on, such as depth sounder, radio, lights, etc and when I turn something else on the whole lot goes dead? After about 10 mins I can get one thing to come on again without touching anything.
Checked fuses, no problems, checked most of wiring, no loose wires. Driving me nuts! All I can suppose is that I may have got water into one of the two isolator switches (ones with red removable toggles) when I recently wiped out locker with damp rag? Do I replace these switches? Everything worked fine until I did this. Have tried wd40 on them.
Boat on a swinging mooring so need to get out to it to test things. Any ideas?

Take a length of say 1 sq mm wire 5 metre long, strip back one end, twist tight around the multimeter neg probe, wrap tape round. Attach the other end of the wire direct to the battery neg terminal.

You can now check the voltage, both positive and negative, relative to a fixed known point. When you loose power, you can start at the battery and work your way along the cabling looking for the change in voltage. A fault in the positive line will see the voltage fall, a fault in the negative will see the voltage rise.

Brian

 

[deanhomer]

Most likely a loose connection in the supply to the panel or neg bussbar.

Check all connections are clean and secure, it is good practice to do this once a year. Onnec clean and secur coat all main supply connections with 'Lanocote' or vaseline.