"My dryer is not getting hot," is a quick money maker. It means one of several things, each of which are easy to figure out. In sequence of likelihood:
1. A bad thermal fuse on the side of the heater box. Unplug the dryer and ohms test the thermal fuse and the high limit on the heater box (limit is much less likely). Of course remove a wire from each component so your meter and you will not be fooled. Replace if open circuited.
Samsung Thermal Fuse
2. A problem in the gas valve assembly such as a bad coil or igniter. See Gas Valve Testing 1 and 2. Test for 110VAC coming in to the valve either with a meter or by listening for the gas valve click. Are you sure that you have gas??
4. We are now into the rare. Are you sure your tests so far were accurate? OK, double check that 110vac is or is not entering the gas valve. If the answer is a confirmed "No", then you are into the unusual.
1. A bad timer, computer board or thermistor.
2. Bad control thermostat - very unusual.
3. Bad motor centrifical switch - very rare.
4. Bad heat relay or even heat board on Whirlpool products.
Whirlpool Heat Relay
Whirlpool Even Heat Board
These will require tracing the circuit using the schematic or tech sheet for your specific dryer. The tech sheets for the Whirlpool dryer shown here tell you exactly how to test this circuit.