furnace doesn't run at times

[swideen]

Most of the time my furnace works fine.

Sometimes, however, it will get much colder than it should and the furnace won't turn on for awhile. For instance, the digital thermostat is set at 67, and it could get as cold as 61-62, so I check the thermostat, and the HEAT light is flashing like it does when the furnace is running, so it appears to be 'trying' to heat, but nothing is running. It will continue flashing HEAT until it eventually kicks on, sometimes a long time later.

I can always turn OFF the thermostat, turn it back on and the heat furnace will immediately kick on.

Any idea what is causing this and how to fix it? I bought the thermostat last year. This was happening with the old thermostat as well.

[imeduc]

Batteries ok in the tstat if they are there? Jump R to W if the burner comes on it can be in the tstat there. If also in the old tstat can be down in the furnace board.

ED

My mistakes dont define me they inform me.

[Hube]

As was mentioned by Imeduc, check the board out. If your lucky, it might only be a bad connection /loose terminal.

[LazyPup]

The post states that the furnace doesnt run at times, therefore i conclude that this problem is sort of hit or miss.

I am wondering if this is an oil burner or perhaps a gas furnace with an electronic pilot and the problem may be an intermittent igniter sequence.

I would definitely check the igniter components to be sure they are working correctly.

[swideen]

It is gas with electronic ignition, that was replaced lastyear

[clayton1]

Check the grounding from the flame control to the actual ignitor in the burner. May have to run a ground from the controller to the ignitor bracket to assure reliable grounding of the ignitor. Doing it through the frame is not sufficient since the ignitor is mounted on the burner itself and it physically floats by design.

I had this same problem and a new ground wire to the ignitor fixed it. I have an old Armstrong gas furnace. Sometimes when they do retrofits they forget to do this.