<VV> Electrics

[Hugo Miller]

I have the passenger seat out of the '64 convertible I'm rebuilding, 
and I've been lying on my back in the passenger footwell (looking for 
somewhere to hook up the radio). So I'm looking at things you wouldn't 
normally see. In doing so I have found a couple of things I can't 
identify. There is a silver box just to the left of the glove box, 
smaller than a relay, with two fat yellow wires going to it. They may be 
yellow plus something else, but predominantly yellow. They are permanent 
+, or rather one is, and that energises the other. I'm thinking it might 
be a circuit breaker of some sort?
And something I've never seen before - there is some kind of sensor 
inside the right hand demister vent. What on earth does that do?