I suspect the switch works like this

Power: car system supplies power to battery

Car: Battery is isolated from from car charging circuit

You would need to check how the switch works with a multimeter to see if this is correct can you do that or know someone who can help you with it

Yes Dodger I agree.

Now I have always left the switch set on power.

The car has an anderson plug hook up to the van so does that mean I switch over to car when I use the anderson?

It may sound obvious but I want to be sure.

looc21 wrote:

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Yes Dodger I agree.

Now I have always left the switch set on power.

The car has an anderson plug hook up to the van so does that mean I switch over to car when I use the anderson?

It may sound obvious but I want to be sure.

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 Here is what I suggest you do to make sure all is A OK.

Connect car as normal and start engine, next turn the fridge on to 12v and place the power/car switch in the car position wait about 30minutes  then feel the exhaust part on the out side of the van above fridge if it is warm then all is working ok. 

Do not turn car off while doing this trial but let it at least idle the whole time.

This is a laymans way of testing, the other way is by a multimeter if you know where the 12v connections are at the rear of the fridge.

They are usually on the bottom of the fridge behind the outer air inlet below the fridge and the exhaust vent.

It may not take 30minutes if the fridge is not in use.

Hope this helps. 

G-Day Looc21
Ours works as One Dodger said. Took me a while to work out too.