On a gas dryer that is shows signs of not heating properly, the source of your issue could be the flame sensor or the gas valve solenoid or coils. On the gas valve in the dryer are several coils that primarily open and close the valve responsible for the flow of gas. If a coil fails, the gas will not turn on and the dryer will not heat properly. Take these steps to test the solenoid.
Step 1 - Power
Be sure to first unplug the dryer’s electricity to avoid electrical shock. Remove the access panel and set it to the side with the screws so they do not get lost during your inspection of the gas valve solenoid.
Step 2 - Adjustments
Select a high heat setting on the dial and then turn it on to observe the flame sensor. Watch as it changes in color. If it glows for several seconds then you will want to replace the gas valve solenoid. If the ignitor glows and stays lit for a longer time, then the problem is going to be found coming from your flame sensor. If it goes out quickly you will want to check your air intake nozzle.
Step 3 - Testing
Test the gas valve solenoid for electrical issues using a multi-tester. Simply set your multi-tester to the ohms setting of X10 and place a probe on each of the terminals. What you are looking for is a change from an infinity reading to roughly 1300 ohms. If the device reads either infinity or zero ohms, the coil should be replaced.