Hello - thanks in advance for entertaining my questions.

I have a 1994 York furnace --forced air/natural gas.

When I turn the thermostat to "heat" the heat refuses to turn on. No clicks, no blowing, nothing.

However, the A/C and the "fan only" work fine.

I replaced my thermostat thinking that would solve the problem, but it didn't.

I appreciate any troubleshooting advice that you can give. Let me know if you need additional info. Thanks!

What is the model of this furnace? Is it 80% or 90% eff?
What control board does it have 50A50 or 50E47?