I have a Rheem upflow mid efficiency furnace with inshot burners and pilot light. It worked until last night and now when you turn it on heat or turn the temperature up the heat won't kick on. Its at 67 right now and I'm calling for 74 degrees. I've got young children in my home and its getting cold. The furnace was probably installed when the house was built in 1960 also the pilot light is lit and working.

Please help:(

i have a Rheem upflow mid efficency furnace with inshot burners and pilot light. it worked until last night and now when you turn it on heat or turn the temperature up the heat wont kick on. its at 67 right now and im calling for 74 degrees. ive got young children in my home and its getting cold. the furnace was probably installed when the house was built in 1960 also the pilot light is lit and working.

please help:(
I believe the gas valve is gone

Usually there is a 24 volt AC transformer in the furnace with the secondary winding connected to a red wire running to the thermostat and a blue wire, common, to the gas valve, A/C relay, and fan relay. From the thermostat there will be white wire to the gas valve. The thermostat is wired to switch the red to the white when it calls for heat. Older furnaces had a limit switch that closes a relay turning the blower on after the furnace heats up. The transformer, limit switch, and relay may all be combined in a fan control center, or be separate parts.

Check for voltage, then for the pilot light to be on, then the gas come on, and finally if the fan doesn't start, another limit switch will shut the gas off. There is more info in the sticky at https://www.askmehelpdesk.com/heating-air-conditioning/heating-cooling-maintenance-repair-troubleshooting-frequently-asked-questions-58313.html but much of it is for newer furnaces.

The limit switch part was right but I figured it out before I looked at this answer

Thanks for your answer. It was the limit switch not gas valve. If it wasn't the switch, I would have went to the valve.