Bongo Fury

Quick update and a thank you for the advice. Piggy back fuse fitted nicely, extra fuse box added and an inverter behind the glove box as a bonus. I did need some special spades to get into the fuse box circuits but all seems good - thanks for your help.

Hmm. Embarrassingly after thinking all was well, it looks like the leisure battery is not charging. There is power feed to the relay and a 2.2v drop across it. I also can't get a voltage from the relay trigger, which I have taken from the IG2 circuit (fuse 16). Can you please confirm when that ought to change from 0 to 1 and back again? I presume measuring it is as simple as reading the voltage from the trigger spade on the relay to earth?

Also, I assumed the IG2 circuit wouldn't work if the fuse was out of the piggy back holder but the engine still starts fine. Any ideas?

Check with a voltmeter that you are getting full battery voltage (>12volts) from the IG2 connection when the Ignition is on, if yes, then check that the other end of the relay coil is connected to earth/chassis, it sounds like you might have a problem with one of the connections. You expect to see a full 12volts across the coil of the relay when the Ignition is ON.

You say you get 2.2 volts across the relay ? Do you mean the coil or the contacts ?

Fixed. Dumb old me hadn't clicked that the piggy back fuse needs two fuses in the back (one for each circuit) , not just one. It then pulled 25A and brought the leisure battery back up to its original voltage. My naivety exposed, but hopefully others can then avoid the mistake!