12v system problems

[mercer_1987]

Hi I’ve recently bought an eldis autoustrarus eb as a bit of a do up project, when I run the interior electrics on the main battery the interior lights run fine, but when I switch over to the leisure battery the lights come on fine but in less than a minute everything goes really dim and almost turns off as if the battery has died, when I switch it if and back in again it repeats this, it’s had a new battery put in and has been tested so I know that’s fine, also the ceiling fan doesn’t seem to work on the 12v system either, any suggestions would be greatly appreciated as this is all new to me, thanks

 

[Guigsy]

It sounds very much like the battery has died.

 

[Riverbankannie]

It is odd if you have put a new battery in. However also being able to run interior electrics from “main” battery (not sure if you mean the vehicle battery here) is also very odd and I would assume someone has been fiddling with the electrics.

 

[TheBig1]

If it's not a dead battery, it is most likely a bad connection on or near the battery

 

[mercer_1987]

This is what happens at the moment

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[mercer_1987]

This is what happens at the moment

This is what happens at the moment

 

[autorouter]

You need to get a multimeter to look at the voltage of the batteries when you do the switching you describe. You can get a lot of information from a few voltage readings.

For example, put the probes on the actual leisure battery terminals. Note the voltage. Then turn on the light and see if the voltage stays high, or falls off rapidly. If it stays high but the lights go dim, then it's a wiring/connection problem. If the voltage falls off rapidly, then at least you know and can look for a cause. If the battery is new, maybe it is faulty. Or there could be a big amps drain somewhere.

There are all kinds of theoretical possibilities, but a few voltage readings will home in on the problem. Are you OK with using a multimeter?