My Lennox G 20 furnace starts up well but the gas valve doesn''t open. A repairman said there was voltage to the gas valve but insufficient to open it. He suggested the ignition module. As both of these parts are expensive and only one is faulty, I am wondering if this diagnosis sounds plausible. Would an ignition module sent electricity to the gas valve in an insuffient amount? It is a low voltage gas valve (24v) Isn't it just as likely something is blown or jammed in the gas valve?
Ideas?
BW