A-4 trailer lights

Here are my golf inner tails on stock housings afaik.
One pin plug

Three pin plug

Whole housing.

After romad’s post I noticed that in daylight you can see the letters corresponding to each pin are embossed on the hosing, so if you can see the things you might not need a tester to figure it out

I see I mixed up the ground and tail locations and although I have a 15amp fused 12v plug, it is too high an amperage to do any good, so the mix up crisped it but did no real damage, except for that which was done to the 23 position 5 amp mini fuse! Replacing that and properly wiring the 3 pin plug fixed the tail light.
The 12v plug needs a 15amp fuse to keep from getting too hot, but the powered converter requests 10 amp protection, I'm getting about 11.5v out of the 4 flat trailer plug. I wonder if I should patch in a 10amp inline fuse before the converter.

My converter uses a cigarette plug with a built in fuse but I can't remember if it is 10 or 15 amp.

Edit: Just checked and it is a 10A 32V fuse.