Disco 2 12v live wire needed, but only live after engine is on

Hi,

I am trying to source a wire that is only live after the engine has started, ie not live when the engine is cranking.

needed for the towing electrics to turn the power on for the fridge and battery charging wires.

thanks

The usual option is to use the alternator warning light connection. This will be at 12V when the alternator is generating power. Alternatively, use a voltage-sensitive relay which will be self-switching and can be wired independently of any of the car's circuits.

Remember too that with a post-1998 caravan, you don't need a separate feed for battery charging as this is handled in the van.

When the engine is cranking there's no power to the position 3 terminal in the ignition switch so all you need is a relay controlled by anything on that circuit.

Remember too that with a post-1998 caravan, you don't need a separate feed for battery charging as this is handled in the van.

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I'm not sure I agree with the above statement - if you look at the 13-pin wiring there are separate feeds for battery charging and fridge. The former however is controlled by the latter.

thanks guys ... I was going to use the battery charging wire to charge my 2nd battery in the boot, but after some research I have decided to do a proper job and get a decent split charge relay kit.

iansoady said:

I'm not sure I agree with the above statement - if you look at the 13-pin wiring there are separate feeds for battery charging and fridge. The former however is controlled by the latter.

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What I mean is that there's no switched power supply at the car side for battery charging. This is handled by the continuous supply (Pin 4 on the 12S) with switching done by a relay in the van controlled by the fridge circuit.

I've installed the towing electrics on my transit for our caravan. I felt it was Easyer on my 2010 transit to use one of these. As I don't have a second battery,

http://www.split-charge-relays.co.uk/contents/en-uk/d13__smartcom-split-charge-relay.html

My winch challenge truck has an albrite split charge and I've got a few bit todo to it and one is to throw it away as its only every ised off road with 2 new identical battery's,

You could wire the smart relay in at the rear of the car off a 12v + straight off the battery on a fused supply. it will make and brake as required.

I've never had a flat battery with the caravan plugged in and the van off.

If you use a split charge relay it will need a feed off the Altenator and you will flatten the second battery unless you install the split charge on the feed to the towing electrics.

Hope this all makes sense

thanks

this is the reason why i need this info

https://www.landyzone.co.uk/land-rover/unproductive-sunday-afternoon.292442/