Dryer cuts off soon

DRYER OVERHEATING:

Heating Element
A defective heating element can make a dryer too hot. If the element partially shorts out, it can produce heat all the time, regardless of whether the dryer is calling for heat. Remove the heating element to inspect it. The coils should not be touching each other or anything else.

Other Causes and Conditions
Air Flow Problem
Dryers need good ventilation to work properly. If the vent is clogged it can make the dryer too hot. Clean all of the vent tubing thoroughly.

Cycling Thermostat
Although not common, a defective cycling thermostat can make the dryer too hot. The cycling thermostat is supposed to turn on and off the heat to maintain the proper temperature. If the thermostat is defective it may keep the heat on too long. The thermostat is not adjustable or repairable, it must be replaced.

Felt Seal
Most dryers have a felt seal at the front and rear of the drum to keep the heat inside the drum. If the felt seal is worn away or missing, the dryer may keep heating and make the dryer too hot. This is not common.

Blower Wheel
A defective blower wheel will not spin properly and will not vent the hot air, making the dryer too hot. Check to see if there is adequate airflow out of the dryer.
https://www.youtube.com/watch?v=3m5NZvY9V5Q




Gas Dryer no heat: or shuts down soon after heating CHECK:

Thermal Fuse
If the air flow in the dryer is restricted, the temperature in the heating chamber can get hot enough to blow the thermal fuse. If the fuse blows, it cuts power to the coils that control the gas valve. The fuse is usually mounted to the exhaust duct just inside the back panel. You can check its continuity with an ohmmeter. If, after disconnecting the fuse, you get any reading other than 0 when you touch the leads of the meter to its terminals, it has blown. There's no way to restore it -- you'll have to install a replacement.

Igniter and Gas Valve Coils
TEST with a multi meter: The igniter is an electric conductor that works like the element in an electric heater, glowing hot enough to ignite gas when you turn on the dryer. This conductor can burn out, and when it does, it may glow, but it won't get hot enough to ignite the gas. At times it may give a reading of continuity yet fail mechanically and not get hot enough to ignite flame though it gets hot and glows and even may show Ohms or continuity ( close circuit) ?

Occasionally, the Gas safety valve and the electric coils that control the gas valve are defective -- they can wear out when the dryer gets old. When this happens, the igniter glows, but gas never enters the heating chamber or does not stay consistant.
Performing a continuity test on either part will help you determine whether or not you need to replace it. But the coils should also be tested for amount of resistance as well as Ohms. As they may be showing ohms yet not putting out enough resistance to keep proper gas pressure flowing. Most coils should show at least 1300 ohms ( GIVE OR TAKE 150 OHMS). Anything significantly less Thus u get an ignition but then it soon goes back out. The flame does not stay lit.

Air Flow and Heat
The motor that drives the tumbler also drives a fan that circulates air through the heating chamber and the tumbler and expels it through the vent. If the air can't circulate, perhaps because of lint blockage, the heating chamber overheats, which prompts the cycling thermostat to turn off the gas. The thermostat resets when the chamber cools, but the chamber heats up quickly and the thermostat again shuts off the gas. The result is that the temperature in the tumbler doesn't stay hot, and your clothes take longer to dry, if they get dry at all.

Warning
There's a big difference between a dryer that doesn't heat up at all and one that just doesn't get hot enough to dry your clothes. In the first instance, the problem is usually a defective part, and things should be back to normal after you replace it. In the second instance, the problem is caused by restricted air flow, and you need to clear the lint filter and vents and take steps to prevent lint build-up. If you don't, you'll use more energy for drying than you need and the dryer may continue to malfunction. Worse, you may have a dryer fire.