I have provided a checklist for both gas and electric dryers, courtesy of; www.repairclinic.com
They also provide repair parts, disassembly diagrams, and instructions.
Firstly, ascertain that you have made a positive heat selection, then read on.
Warning! To avoid personal injury or even death, always disconnect your appliance from its power source--that is, unplug it or break the connection at the circuit breaker or fuse box--before you do any troubleshooting or repair work on your appliance. Also, because some components may have sharp edges, use caution while working on your appliance.
Electric Dryer Checklist:
If your dryer doesn't heat, check these:Power from the houseHeating elementThermal fuseWiring
Power from the house
Check to see whether there's power getting to the dryer. Is it plugged in? Check for blown fuses or tripped circuit breakers--your dryer uses two fuses or circuit breakers. The dryer could tumble but not heat if only one of the two fuses is blown. If you have circuit breakers, one of the two circuit breakers can trip, even if the two for the dryer are connected.
Often a dryer heating element burns out, but doesn't trip the circuit breaker or blow a fuse. The heating element is simply a long coil of special wire. You can check it for continuity with an ohm meter. No continuity means the element is bad and you need to replace it--electric heating elements aren't repairable.
On many dryers, there's a thermal fuse mounted to the exhaust duct inside the back cover panel. The fuse--which is about an inch long--is usually embedded in black resin and mounted in a white plastic housing. If the fuse has blown, you need to replace it. (You can't re-set it.)
A common problem is for the main wiring connection from the house, at the dryer, to burn and break its connection. Because the dryer can still tumble with partial power, the connection may be only partially defective. You may need to replace both the power cord to the dryer and the terminal block inside the dryer that the wire is attached to
Gas Dryer Checklist:
If your dryer doesn't heat, check these:IgniterGas valve coilsThermal fuse
Modern gas dryers use an electric igniter to ignite the gas from the gas valve. When it's working properly, the igniter glows bright orange. When it burns out, the dryer tumbles but there's no heat because the gas can't ignite. When the igniter burns out, you need to replace it. If the igniter is held by a tension bracket, you very well may need to replace the bracket too.
The igniter is inside the dryer housing, near the bottom front, usually in a cone-shaped metal tube (the force cone). It's about 2 inches long. It's mounted to the far end of the burner tube, and it has two wires attached to it--or to the tension bracket, if there is one.
Gas valve coils
Watch the igniter. Does it glow bright orange, then shut off without igniting the gas? (When the gas ignites there's a large blue flame.) If so, there may be defective coils on the gas valve. Mounted on the top of modern gas valves, there are black electrical coils. The coils, when energized, open the gas valve. If one or more of the coils are defective, the valve doesn't open and the gas cannot ignite. Because it's often difficult to properly test the coils, it's usually best to replace both (all) of them at the same time.
On many dryers, there's a thermal fuse (a heat-sensitive fuse that blows if the dryer overheats) mounted to the exhaust duct inside the back cover panel. The fuse is about an inch long. It's usually embedded in black resin and mounted in a white plastic housing.
If the fuse has blown, it has no continuity. When this happens, your dryer either just stops heating, or it doesn't work at all. Be sure to inspect the venting/heating system before replacing the fuse to put the dryer back into operation. (You can't re-set this type of fuse.)