I can't keep the flames going on my Bryant furnace. I have two units, upstairs and downstairs. Upstairs is working fine. Downstairs- I followed the instructions to "relight", the coil got hot, the flames came on, but after a few seconds shut down. It makes two or three attempts, then shuts down altogether. Although after leaving my thermostat at 70, the blower comes on every now and again. I went downstairs and its still attempting to fire up, but again shuts down. I adjusted the "heat anticipator" to 1.0 based on an earlier question/answer I saw, but that still didn't fix it. Any suggestions?

Try cleaning the flame sensor .Should be located in front of the burners with the ignitior( the one that glows when trying to start)on one side and the flame sensor on the other ( with one wire attached to it) remove and clean with fine sand paper or scotch brite pad. Reinstall and check operation.

If you have no flame start up at all on the furnace you have dirty burners or a bad gas valve.