Make sure that you have an adequate gas supply provided to the dryer and that the gas cut-off valve behind the dryer is fully open.
The first step in troubleshooting this heating problem is to take out the observation plug in the front of the dryer cabinet and observe the burner assembly with the dryer running in a heated cycle. See if the igniter is glowing. If not, then I recommend shutting off the dryer and
unplugging it to disconnect electrical power.
Shut off the gas supply and pull off the back panel. Check the thermal fuse that is on the blower housing for continuity with a volt/ohm meter (with the dryer still unplugged). The location of the thermal fuse is shown in the first image below. NOTE: Your dryer will be slightly different than the one shown but the thermal fuse is in the same location.
To check the thermal fuse (with the dryer unplugged), pull one wire off and measure the resistance across the leads of the fuse with a volt/ohm meter. You should measure near zero ohms of resistance (closed) if the fuse is okay. If you measure infinite resistance (open), then the fuse is blown and will need to be replaced. To verify that this is the only failure that is preventing the igniter from glowing, you could tape the wires that connect to the thermal fuse together will electrical tape and then test the dryer to see if the igniter glows and the burner ignites. If it does, then replacing the thermal fuse should fix your dryer problem. NOTE: Do not continue to run the dryer with the thermal fuse bypassed. It is an important safety component that must be replaced.
If the thermal fuse was blown, I recommend checking the exhaust vent system for the dryer. Make sure that the lint screen is cleaned before every load. Check the flexible vent hose behind the dryer for a kink or lint clog. Check the exhaust duct system to the outside of the home for clogs or restrictions. If your vent duct runs up through the roof of the house, you may need to have an outside service clean the duct. Make sure that the damper on the vent at the outside of the house is opening properly. These tips will help prevent the thermal fuse from blowing again.
If the thermal fuse is okay, then several other components could prevent the igniter from glowing. The wiring diagram for your dryer is shown in the second image below. An open operating thermostat, high limit thermostat or flame sensor could prevent the igniter from glowing. You could also have a failed timer contact, an open contact in the motor centrifugal switch or a wiring failure between components. You can check the operating thermostat and high limit thermostat in the same manner as you checked the thermal fuse.
If the igniter is glowing, you could have a failed flame sensor or bad gas valve solenoid coils could prevent the dryer from heating. The third image shows the theory of operation for the gas valve assembly. Understanding this theory is essential in properly diagnosing and repairing gas dryer heating failures. Using this information may help you understand the cause of your heating failure.
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