Just had a new towbar fitted, what i,d like to know is, is it possible to plug it into the van to test the lights on the van without the battery from the van fitted, cheers.
Yes.
Battery in caravan powers internal fittings only, not the "road" lights.
You may also have 2 feeds for the battery and the fridge but these won't matter if just testing
Just take care to ensure the clips for the battery terminals are well separated before you do so, otherwise there might be bright flash somewhere.
------------- Bill
For a licence dated 1997 or later you must add together the plated max weight of the caravan and trailer, if the total is 3500 or less you can tow it. You may even tow a caravan with a MAM greater than the cars unladen mass the restriction was removed in 2013
If it's a fairly modern van the inside 12volt electrics (lights, water pump etc) should work from the car battery if the engine is not running.
When the engine is running the fridge should work on 12 volt and caravan battery will charge (if you had one fitted) but the internal electrics will be isolated.
On an older van you may have a switch to select van or car battery etc.
Nothing should work on inside the van when plugged into the car when the engine is not running and when it is it should only run the fridge and charger.