thermocouple is a safety device which holds pilot gas supply open when heated when you release gas valve button. your question states pilot light will not come on which would have nothing to do with tc. if pilot will light but not stay lit after releasing button then tc is fault.
combustion area too so gas installer job, in order to verify eg on apollo's state of h/ex which when dirty will burn with massive amounts of co, so good seal, service and new tc from a local engineer would be my advice
iain, September 2008
