Well, back to the forum. When I left off, the new flame sensor allowed the burner to light, but the flame looked feeble and didn't make the roaring noise it used to have. I put in a full load of wet laundry and turned it on, and it ran and ran (I could feel a little heat inside, but it was not as hot as normal). Eventually it shut off with clothes still wet, and "F2" displayed on the control panel. What to do next?

Well, it was raining today and I couldn't hang my laundry out on the line, so I took the front off the drier to check the thermistor. One of the wires was unplugged from the thermistor. When I plugged it back on, the dryer was able to start. I hope that fixed the problem!

It's still not working completely right. It takes much longer to dry and doesn't get as hot as it used to. The thermistor registers 18,000 ohms at about 67 F, about 20,000 ohms at about 85 F. I zeroed my ohm meter before testing. The igniter heats up red hot. The flame comes on and runs for about 17 seconds, then it shuts off for about 60 seconds, then the cycle repeats. The flame reaches about to the back of the cylindrical burner enclosure, but doesn't really get sucked up into that vertical plenum beyond it. However, running for such short duration on each cycle, it doesn't produce enough heat to heat up the wet laundry like it used to. What's the next thing to test or replace?

Airflow from vent is great, what's the part number for the thermistor? Dryer model is given in the top part of this thread. Could it be the high burner temperature limit switch on the burner duct cone? However, the thermistor is certainly reading high ohms at room temperature. Would that mean it would be falsely reading high temperature in operation?

Put the new part in, ohms on new thermistor are about the same as on old thermistor, so the old one was likely OK. Ran the dryer with a load of wet laundry. Problem remains, same as described above. Flame comes on, shuts off less than 20 seconds later, stays off about a minute, repeats cycle. Lots of air coming out the exhaust. Exhaust temp is not as warm as it used to be (now it's barely warm at all). Contents of dryer never get hot like they used to. The flame is just not staying on long enough to provide the normal amount of heat. What's going on?