My Comfortmaker RPJ II (Gas) is 14 years old.

Everything starts just fine. After 3 to 5 minutes of wonderful warmness the gas flame turns off (way before the desired temp is reached) but the blower continues to run until I stop it. It appears that the blower wants to get to the temp on the thermostat while the gas doesn't really care about that.

Most of the time I can make the blower stop by decreasing the temp on the thermostat. Every once in a while I have to turn off the power to it to make the blower stop.

I see all over the place I need to count the flashes to diagnose the problem. The light that is supposed to flash does nothing, no light at all.

This is getting to be a long for for my first one.

 

Anumber of conditions can cause the furnace burners to shut off.

I'd start by checking the filter to see if it's plugged with dust and dirt. There should only be one layer of furnace filter. Also check to be sure that most warm air registers are open and that the return air grill(s) are not covered over or obstructed.


From there, things get more complicated. Check the pressure switch, if any, to see if it is shutting off the burner. Clean the flame sensor, if there is one, with a wire brush or steel wool.

 

High limiting due to overheating is a good bet, and the reason Seattle mentioned the furnace filter is - if it gets blocked, or even if vents are closed down not letting enough heat out registers, the furnace can high limit and the blower motor keeps running as a natural function to try to cool down the inside of the furnace.

In cases of years of furnace filter neglect, if houses have central air, you also have coils above the furnace; these can get plugged with dust and slow the heat from escaping the furnace.

Also, down low on the furnace, just above the blower, is a secondary heat exhanger where the condensing occurs, and these, if designed with close fins, can also become clogged for the same reason, and not permit the cool return air from passing through it as well, to cool down the heat in the furnace. To access that lower (finned) exchanger you have to remove the entire blower and then lay down under there and vacuum. Not fun, but cheaper than paying to have it done.