Gas and Oil Home Heating Furnaces - furnace operations

I don't know if this is normal or not, please adivse.

Sometimes my furnace gas kicks on for about 5 seconds, goes out for about 10 seconds, then back on for 5 seconds, then out again. After doing for about 2 minutes the blower will kick on.

The other thing that I have noticed is that the gas/flame is on sometimes when the blower is running. Other times the blower is running without any gas/flame.

The heat level in my house seems to be ok - it's staying at 74.

This may be normal, I just never noticed it before.

This furnace is a Trane XE80.

If there is a problem, what could it be?

Thanks in advance!

no it is not normal for your burner to come on for a few seconds. This will be casued by a safety control, either the flame sensor or more often caused by an air switch. When you see the burner short cycling, try opening a window or an outside door to allow combustion air into the furnace room, does it correct the problem?

Thanks for the advise. I checked that and still had the problem.

Most of the time the furnace/flame will come on for a few seconds and then go out. However, on occassions it will come on and stay on like it should. In either case, the blower always kicks on, it just sometimes blows hot air sometimes cold!

I heard something about a resistor possibly being a problem because I put in a Digital Thermostat last year. However, I replaced that with a Honeywell Round and had the same problem.

Any other ideas? Thanks!:)

I think your Flame Sensor is going bad. It's a rod-like metal that
senses the presence of flame after ignition.

It can still be your Air switch or the flame sensor is not reading a strong enough flame signal. or about 100 other things. If your furnace is controlled by a mirco processor than the should be some sort of flashing LED, check the blower compartment, if there is one it will be visable without removing any panels, this indicate the status of the furnace. Air Switch open, retry for igniton, limit open ect... There could be one on the ignition control which powers the spark ignitor or HSI.
If there is a flashing LED than there will be instuction on your furnace or in the owners manual to tell you what the flashing means.
Read the code and call your local service tech.