Gas and Oil Home Heating Furnaces - Tempstar 7000 problems

Hi, I have a Tempstar 7000 installed around 1994 with a Honeywell T87F thermostat. My problem is when I turn the thermostat to the heat setting, nothing happens. After a few minutes the fan will start and either stay on until I turn the furnace's main switch off or just a few minutes. My A/C works fine. Any help would be greatly appreciated and I am will to do any troubleshooting necessary. I am willing to post pictures if need be. Just let me know where to start. Thanks in advance!!!

Look at you gas valve ans see if it is a Honeywell Smart valve. The number on the valve will start with "SV"

No, it's not a smart valve.

I am with Matt on this.. SmartValve are been known to have a lot of problems.

Does it have a standing pilot or, glow rod, or is it electronic ignition. Sounds like you're not firing and the blower is on a timer via the board.

You'll have to be down there while someone activates a call for heating and see what it does and doesn't do in order.

I have electronic ignition. When my wife turns the thermostat up and it calls for heat absolutely nothing happens. Sometimes the fan will start up and run for a few minutes or will stay running indefinately. Other than that, nothing happens, no sparking, no nothing.

By "fan" do you mean the fan for circulating air or the small exhaust fan? If you can supply a model number of the furnace, I might be able to find a service manual.