Quote: Bryn wrote in post #14

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.......what questions should I ask if any?

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In the main, problems only arise around the non wiring up of Pins 10 (positive 2.5mm cable) and Pin 11 (earth for Pin 10, 2.5mm cable). This is mostly historic as in the main towbar use is for your everyday trailer which of course don't come with a fridge lol and it appears just to have carried on this way unless the buyer specifically requests the full 13-Pin setup and even then is prepared to check it's been done correctly later on.

In many cases where the fridge runs even though the engine is not running it is because the fridge has been wired up to run off Pin 9 which is a continuous live feed. On long overnight ferry crossings this situation would of course drain the cars battery and so one often used to see, and even today although to a much lesser extent, users pulling their electrics whilst on the ferry.

Checking that the electrics have been correctly wired up is fairly easy although also a bit of a pain depending on ground clearance of your car. You can lay on your back and take a look at the back of the socket which should reveal 13 wires - one for each pin of course. If there are only 11 then it's a fair bet that the wiring for Pins 10 and 11 have been omitted. If the socket end of things appear OK then with the engine off put one ear to the bottom grill of the fridge outside vent where all should be quite and no warmth felt. If it feels even slightly warm then the fridge is running. Don't rely simply on any external bulbs on the fridge itself as the internal light and probably the outside indication are wired to Pin 9 (continuous feed) so even though the internal light comes on when the door is opened is no indication that the fridge is running.

Now run the vehicle engine and repeat the above - the bottom vent should start to slowly warm up and a slight audible indication will be heard although the warmth is the main giveaway.