Gas not lighting on boat fridge?

The 3 way Electrolux fridge on my 1978 Fairline Mirage boat works on 240v and 12v but will not light on gas. It has seperate 12v supply for igniter and power is ok at inlet, and to what I assume is the igniter (3x2inch box at bottom corner). But no power out from this igniter to rocker switch or to burner. Is this how the unit fails or something else before I spend £78 on replacement.
Thanks for any input.

Colin Sharp
April 2011