I have a montgomery wards 700 furnace, its natural gas and has no ehaust assist fan and it has a summer fan switch. ( the house is new to me) at first the furnace didn't start. But if you bypassed the thermostat it did. So I purchased a lux heat only model and it started , looked like it ran OK. Then it stopped working. It won't start at all even if you bypass the thermostat. The pilot light is on. I called a furnace guy who came out and told me that the gas valve was bad. 200 to replace. I found one on the internet and installed it. Still no start. But now if you bypass the thermostat you can hear a click on the valve. It seems very simple as it only has the thermostat, fan limit switch, fan motor, transformer and summer switch. The summer switch does make the fan work. There is no information on the furnace and I can't tell you the age of it either. What else could the problem be and where can I find parts for this? Thanks!!

Did you carefully follow all the directions, removing any packing from inside the valve, and turn it to On from pilot?

Did you turn the gas shutoff valve back on?
Homer

Thank you all. I changed the gas valve and still won't come on, but I found out the thermostat was bad so I bypassed it and it would come on but no fan. Suspected the fan limit switch, after talking to a friend I broke down and called a tech. 75.00 later and still with no answer he showed me the exchanger which had cracks in it. So time to forget the issue and start collecting donations for a new furnace. Again thanks.:(