No heat gas dryer will light up coil and drum will spin. Here a clicking sound but never ignites. Just replaced ignition coil and checked flame sensor and thermostats. Not real sure about the gas regulating valve

Check you flame. If the flame is very short (less than half way down the burner tube, it can be a gas pressure regulator failure. They are adjustable but that usually indicated it is about to fail. Make sure the flame ignites every time you hear the relay and solenoid valve click. The is a small panel on the front that can be removed to see the burner and the pressure regulator. The is a glow igniter that comes on several seconds before the gas is admitted. Confirm that works. Check at the dryer vent whether you smell gas once and a while which would be an indication of a failure to ignite.

For what it's worth: You can eliminate 3/4 of your work if you simply watch what the dryer does. Most have a peep-hole in the lower front covered by a small plastic plate. Remove the plate, start the dryer and look into the hole. If you hear a "click" right as you press the start button and the drum turns, you know the motor, timer and door switch is OK. If you then see a dull glow and a second click, ALL the thermostats, fuse-able links, gas igniter and wiring are OK. If you then see the burner ignite with the blue flame, the flame sensor, valve coils and fan are working fine. If you let it run for some time and then suddenly you only see the dull glow, but no click or blue flame, your gas valve coils are defective. (they will work when cool or cold, but not as they heat up from use) This also will stop the timer from moving since the timer runs when the coils are working well (the power to the timer comes through the coils - just figured this out today). If you don't see the dull glow, the ignition/igniter wire/element could be bad. Hope this helps folks. I see in the forums where one individual just says "Ignition coil" every time a gas dryer has a no-heat issue, but a vast majority of the problems comes from the $20.00 gas valve coils that most anyone can replace.

Bad switch or

If the coils are bad the unit will light with flame for 4 - 8 times then all of a sudden the ignitor will glow, kick off with no gas coming threw valve. it sounds like the high limit thermostat is short cycling the flame. This is the thermostat that sits on top of the burner chamber. remove 1 screw from the thermostat and blend it upwards away from the heat. Then plug unit back in and test to see if the flame stays on longer. Click here to see maytag dryer no heat posts. Contact me anytime here. Hope this helps..

The problem could be flame radiant sensor or in most cases the gas valve solenoid coils sitting on top of the gas valves. The radiant sensor must be aligned perfectly with the igniter. The radiant sensor contacts bypasses one of the gas valve solenoid coils and as the igniter heats up it makes the sensor contact trips unbypassing the coil and allowing the gas to flow and be ignited.

The problem is with the solenoid coils, one with 2-prongs and the other has 3, if the radiant sensor is aligned with igniter and working perfectly but no gas is ignited. The buzzing sound is coming from the coils trying to operate the valves. Replacing both coils is the simple and only viable solution.

Check your coils & igniter. Access door usually located in lower right front of dryer. Remove (pry up & out from bottom of panel, if no screws, exposing burner assembly. Set dryer for heated dry and start, you should see the igniter glow bright orange (give it at least a minute) followed by a CLICK sound,(again, a few seconds) this is the coils opening the gas valve, followed by a blue flame for heat. If no glow, replace igniter. If igniter glows bright and no click, replace the coils.

If electric then the thermostat or the heating element has failed.
If gas: First thing to check is the ignitor underneath the drum. (You have to open the panel to see it) It should glow shortly after the dryer starts, then the flame starts and the ignitor shuts off. If the ignitor does not glow then it or the thermostat is bad. If the ignitor is glowing but the gas does not light then the flame sensor may have to be replaced. If the gas ignites but does not stay on either the flame sensor or the coils are at fault.
See also: http://home.howstuffworks.com/how-to-repair-a-dryer.htm

First thing to check is the ignitor underneath the drum. (You have to open the panel to see it)  It should glow shortly after the dryer starts, then the flame starts and the ignitor shuts off.  If the ignitor does not glow then the thermostat is bad.  If the ignitor is glowing but the gas does not light then the gas valve coils may have to be replaced.   If the gas ignites but does not stay on either the flame sensor or the coils are at fault.

The gas burner assembly uses solenoid coils in a circuit with the flame sensor to safely ignite the burner. When the dryer starts a heated cycle, the circuit through those components is energized. The igniter glows until it reaches the proper temperature to ignite the gas, at which point the flame sensor trips open and the current flowing through that circuit is diverted to the gas valve coils so the gas valves open, and the burner lights and continues to burn. If the solenoid coils on the gas valves fail, the gas valves won't open for ignition. If the gas valve coils are weak, the burner lights during the initial ignition sequence from a cold start but it fails to light the burner on subsequent ignition attempts. In this situation, replace the valve coils. I Had the same problem with mine and I fixed for like $25.00 US. Its not hard to do look at the video. Either buy your part from them or to get it fast and not out of this world go to "repairclinic.com