Gas Dryer No Heat
How a Gas Dryer works
Welcome! Is your Gas Dryer not heating up? The problem could be a blown Thermal-fuse, a blown Ignitor Coil, or a defective Gas Valve. Of course it could be something else like blocked up venting or an electrical problem but we will focus on the three main causes. I will take you through the process of how to find and repair the problem which could possibly save you a lot of money in the long run.
A Gas Dryer burns Natural Gas or Propane Gas to heat and dry clothes. The way it does that is what we want to learn. Gas flow in a Dryer is regulated by the Gas Valve. When the Timer starts it sends power to Ignitor Coil to heat up. An Ignitor coil is a small electric powered element that ignites the Gas. The Ignitor Coil heats up until it triggers the Radiant Sensor to open the Gas Valve and let Gas flow down the Burner Tube. Once Gas enters the Burner Tube the Ignitor Coil ignites the Gas then goes off. Now the Blower Fan pulls the heat up into the Drum where it dries your clothes.
But wait, the Gas does not stay on all the time. If it did the Dryer would over heat and burn up your clothes. The heat is therefore regulated by Thermostats that are attached to the Blower Housing assembly. The normal operating temperature of most Dryers is 155F (degrees Fahrenheit). That means a Thermostat that shuts off current when it is heated to 155F is used to shut off current to the Gas Valve and stop the flow of Gas. Once the thermostat cools down to about 140F it closes again and sends current back to the Ignitor coil for it to heat up and start the process all over again.
This ON and OFF process continues throughout the entire duration of the dry cycle. Changing the temperature setting of the dryer only sends power through a different pre-set Thermostat. Medium temperature is pre set at 145F and low temperature is pre-set at 135F.
Now that you know the basics of how a Gas Dryer works it’s time to get to work on solving your Gas Dryer’s problem. The first thing we need to do is determine if your Gas Dryer is “firing up”. If your machine has a bottom access panel, remove it. If it does not then there is usually a small access hole toward the bottom corner of the dryer’s front panel. If you don’t see it could be covered by a plastic cap. Remove the plastic cap with a small flat screwdriver. The goal is to be able to see the Gas Valve while the Dryer is in operation.
Step one. With the panel removed, start the machine and observe the Gas Valve and Burner area. You will hear some clicking noises then the Ignitor coil will begin to glow red.
- If after more than one minute you do not see the coil glowing then you either have a blown Ignitor coil or a blown Thermal-fuse.
- If the Ignitor Coil glows red and stays red for awhile then goes back out then the Gas Valve is defective.
- If the Ignitor heats up and the gas comes on but then shortly goes back out the problem is in the air flow and exhaust system.
Important note. Sometimes the Gas valve lights up and everything seems to be running fine. In this case you should let the machine run for about 5 to 10 minutes then come back and observe the process again. This is because the gas valve coils may work fine until they warm up but when they do they will begin to lose strength and stop functioning. The Ignitor Coil will then begin to cycle on and off without firing up the Gas.
Checking the Ignitor Coil
Checking the Ignitor Coil. The quickest way to check the Ignitor coil is to use a Voltage Detector while the machine is running but to be safe you should unplug the dryer and use a Ohm Meter to test for continuity. Using a Voltage Detector involves placing the tester on the Ignitor wire while the Dryer is running. If there is Voltage present but the coil is not lighting up then the coil is blown. If there is no Voltage present then the problem is somewhere else, like a blown Thermal-fuse.
The safe way to check the Ignitor Coil is to check it for continuity. Insure that the dryer is unplugged from the power source then unplug the Ignitor Coil’s leads. Using an Ohm meter, check for continuity between the two wires of the Ignitor. If the coil is good you should get a reading between 50 and 400 Ohms. If the coil is blown then you will get no reading. If you get no reading then you will have to confirm that the coil is blown by removing it and visually inspecting it.
The coil is very delicate so be careful when taking it out. Upon visual inspection a good coil should have a smooth consistency. A defective coil will usually have a visible hairline fracture.
Checking the Thermal-fuse
This is done if the Ignitor Coil does not light up and there is no power to it. The Thermal-fuse is a small white thermostat-like component. It is usually attached to the vent near the Blower compartment. In some machines they are round in shape while in others they are rectangular. Unplug the dryer, locate the Thermal-fuse and remove the wires that are attached to it. Now set your Multi-Meter to the resistance setting and check for continuity.
In checking for continuity you place one lead from the meter on one prong of the Thermo-fuse and the other lead to the other prong. If you get continuity then the Thermal-fuse is fine. If you do not get a reading then the Thermal-fuse is blown and needs to be replaced. Thermal-fuses usually cost no more than $10 and can be found at your local appliance parts retailer or you may even find it for next to nothing on eBay. Make sure that you have your machines Model number and Make before you go searching.
Checking the Gas Valve.
This is done if you have established that the Ignitor Coil is coming on but the Burner is not firing up. A malfunction in the Gas Valve usually occurs when the Solenoid Coils that open the flow of Gas in the Gas Valve get weak and burn out. The Solenoid Coils are located on the top of the Gas Valve. After testing the Coils and establishing that they are good there is no need to check the Gas Valve any further. So lets go ahead and test the coils.
In order to test the Gas Valve coils you will need your Multi-Meter. Disconnect the wires that are connected to the two coils. With your meter set on the resistance setting check the coils for the following readings.
- Between 1 and 2 your meter reading should be about 1365 Ohm +/- 25 Ohm.
- Between 1 and 3 your meter reading should be about 560 Ohm +/-25 Ohm.
- Between 4 and 5 your meter reading should be about 1220 Ohm +/- 50 Ohm.
If any of your readings are out of the ranges listed above then you need to replace the Coils. The coils are held on by a metal bracket with 2 screws. Once you remove the metal bracket the coils can then be lifted off the shaft they sit on. The coils are not interchangeable so pay attention to which goes where.
Now that you have performed these basic tests on the Gas Valve, the Ignitor Coil and the Thermal-fuse I hope that one of them was the source of your Gas Dryer heating problem. Remember to have your machines Model Number and Make before you go looking for the parts that you need. If none of the components that you tested turned out to be the problem then you may have a more serious problem and you need to call in a Service Technician. You may possibly have a problem with a sensor, the wiring, or the Timer unit. Good luck in your efforts.
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