The following link is for my thread with a similar problem. These folks here are mad busy, so I pushed through it myself.

http://forum.appliancepartspros...-heat-does-not-stay.html

The gas solenoids ( coils that open and close the gas valves ) seem to be the most intermittent type of a failure...as opposed to a thermostat going bad, or the ignitor having an open circuit.

I checked continuity on the high and low thermostats ( mine are side by side, bottom front ), they have their ranges on them, pink and blue.

Checked the continuity of the cycling thermostat, mounted on the heater box ( where the flame goes ).

Checked the continuity of the flame sensor, mounted on side of flame area.

And checked the ignitor as well.

All were good. The gas solenoids ohm'd out according to specs I found, BUT, that does not say anything about the health of the solenoids when a current is introduced.

Since the other components in the heating circuit were good, I replaced both solenoids, and that fixed the problem.

Like I said, I hacked my way through this, it's your choice to check what I did, or wait until someone (a professional ) chimes in to help out.:o