[mike n]

It's not the switch or the gas valve wouldn't open you need to unplug the igniter and put two meter leads in the holes of the plug with the furnace off, set your meter to volts ac then turn the furnace on after purge you should get a voltage reading if you do the igniter is bad you should have a local rheem distributor but if you don't rheem or ruud either one can sell you the same part.