Have a BOSCH Vision 500 Natural Gas Dryer. Dryer would not heat and could smell gas after trying to start. Dryer is approx 4-5 years old, but looks like new inside. Dryer tumbles fine and air dries, but burner will not ignite. Belt sensor is OK. Vent is clean and all lint has been removed from dryer and vent pipe. Wiring connectors are all fully seated and clean.
Before I had time to take the dryer apart and attempt to diagnose the problem, I simply ordered a new igniter in hopes that that was the issue. Replaced igniter (Bosch #00491648) last night, but that was not the problem. Igniter glows red hot for perhaps 15-20 seconds, and then shuts off. Does not appear that gas burner even attempts to ignite. After I shut off dryer, I can smell gas. According to literature, it appears the Flame Sensor or the Gas Valve Coils may be at fault. Any thoughts on which one is at fault or how to check operation so I know what to order. Thank you in advance for your advice.