The dryer heated up for a few minutes and then cooled down.

1 Unplug power.
2. Remove the front of the unit by removing the two screws at the bottom of the front panel. Front dryer panel will swing out from the bottom and then the clips will release the top of the panel, careful not to disconnect the dryer door switch. ( can be unplugged to remove the front panel out of the way.)
3. Looking inside the unit on the right side you will see the gas value. On top of the gas unit you will see two small coils the coil closest to the burner has two leads on it. Remove the two screws to get to the coils, remove the medal plate, remove the connector then lift off the secondary coil. Replace and test. You can test unit with the front panel off. (be careful). If no heat, check that the Flat Style igniter is glowing. (ohm out both coils) before ordering parts. Intermittent heat problems. I replaced the secondary coil, it did ohm out o:k but it had swollen and was very tight on the shaft.