You can get a clamp meter which will measure DC current.
Indeed you can. It just goes to show people shouldn't believe everything I tell them
The multiplug is on the left hand side of the car (passenger side for right hand drive models) or the opposite side to the fuel filler flap.
I've just been and had a poke around in my boot, and access to this connector is a piece of cake. Forget everything I've said about unscrewing stuff, here's how to do it:
Remove the parcel shelf and give a good hard tug on the plastic moulding with the boot light and lighter socket in it. The rear should unclip quite easily.
A slot in the carpet is hooked around the mounting, so you'll need to unhook it. You can then fold the carpet down. This will give you sufficient access to get at the connectors.
Meter out the wires with respect to a good, known earth, as Renault change their wiring colours more often than some people change their socks.
Finally, have a piccy, just so you can be sure where you're up to. The connector you require is the large completely blue one to the right of the centre of the picture. You can see where my towbar lighting wiring has been attached using crimps and Scotchloks.
It took me less than 5 minutes to grab that picture and put everything back together, so it's really not a major job.