Low voltage to gas valve

[Plumber69]

Sometimes I get 24 volts to furnace gas valve sometimes 10 volts. So obviously it won't fire at 10v. I'm leaning towards board. Can a faulty thermostat cause this

 

[hj]

Usually low voltage is either a bad transformer or something is causing two or more items to connect in series.

 

[Sponsor]

 

[Fitter30]

Take a pic of the wiring diagram inside of blower door. There are to many different scenarios how furnaces fire to to tell u without a diagram.