Dryer Is Not Heating

If the dryer ventilation restriction is completely removed and no heat is produced, then you should diagnose the problem. When a dryer doesn't heat, there's a good chance that the hardest-working component, the heater, is the problem. If you inspect the heater and find that the resistance wire inside the heater is broken then you have found the problem. Remember that for the heater to fail, it would have to be full voltage.

So don't make it more complicated and suspect that the timer is faulty or something. However, it is possible that the control thermostat is stuck and the heater has been operating on the high limit thermostat. But you won't be able to interpret that until after the heater has been replaced. There is no point in checking the control thermostat contacts because we know they are closed. We know this because for the heater to fail, the control thermostat contacts must be intact to allow voltage to be applied to the heater.

If there is no obvious break in the heater resistance coil, it may still be defective. The next thing to do is isolate the heater by removing one of the terminals that supply voltage to the heater. If you are not sure of its capacity, you can remove both terminals supplying voltage to the heater. You can now use an ohmmeter to check the resistance of the heater. A good drying heater will show resistance in the range of 5 to 30 ohms. If you are using a digital meter (by the way, we recommend you use a digital multimeter), touch the two wires together so you can see what happens when your meter reads zero resistance.

Notice that when you touch the two wires together, the meter display drops to zero, indicating zero resistance. When you separate the two wires from the meter, look at the screen to see what happens. Most of the time it will only blink, depending on which brand multimeter you have. When you put your multimeter's wires into the heater terminal, if the heater is open, in other words, broken in a place that is not obvious, the meter will continue to blink. This means that the heater must be replaced.

Sometimes when you get to the heater element of the dryer to inspect it, you will find that one of the wires supplying voltage to the heater has been burned in half. If you find that wire leads to a half burned heater, you do not have to check the heater. For that wire to fail, the heater would have to be producing heat, and current would have to pass through the wire. Of course, you will have to repair the cable, but you should look for a ventilation restriction or other condition that is causing the dryer to get too hot.

This is actually a common problem with dryers that have the heater located behind the drum, such as Frigidaire and GE dryers. The problem occurs when the customer opens the door to remove their clothes before the end of the cycle. When this happens, the heater is fully operational and has not had a chance to go through the cool down cycle. The heat from the heater radiates to the cable lugs and sometimes causes them to deteriorate or become brittle.

If you find the dryer heater is good and the wires going to the heater are not faulty then you should check the dryer control thermostat and the high limit thermostat, sometimes called a safety thermostat or fuse link. Again, with your meter set to read ohms, remove the wires to the thermostat, and check for continuity. Unlike the heater, when you read the resistance through a thermostat, it will show zero resistance. If the meter blinks indicating infinite resistance, then that thermostat is faulty.

All tumble dryer control and high limit thermostats will have normally closed contacts. If you find that a high limit thermostat or safety thermostat is defective, you should check for a dryer ventilation restriction. If all the high limit thermostats and safety thermostats are good, then you should proceed to the next step in the circuit. Making sure the heater is now reconnected, and that all wires to the dryer thermostats are connected, the next thing in the heater circuit is the heater switch contacts on the centrifugal switch, connected to the motor.

The motor's centrifugal switch is designed to close a set of contacts that allow current to flow to the heater when the motor reaches full speed. The easiest way to verify these contacts is to use a jumper wire with alligator clips. Connect the jumper wire through the wires in the heater circuit at the centrifugal switch. It is not necessary to remove them from the switch. Make sure the dryer timer and temperature selector switch are set to heat.

Now connect the cables of your digital multimeter, making sure it is configured to read ohms, on the left and right blades of the dryer cable. Some dryer cables have three conductors and others have four. Either way, route the cables from your meter to the blades on the far left and right. If you read the heater resistance now, then you know the dryer motor's centrifugal switch is faulty. If the meter continues to flash infinity, do not remove the jumper wire from the centrifugal switch on the motor. We will leave it there to simulate that the motor is accelerated so that we can check the heat contacts of the selector switch and the timer.

At this point, you will have to read the schematic diagram and/or the electronic control/timer sequence table, for your particular dryer model. If no timer or electronic control sequence chart is available, you should look at the cables connected to these items and follow them. An electronic dryer control will have a heavy-duty relay or a separate heat control board with the relay. Either way, look for heavy-duty cables going in and out of a relay. You can use an additional jumper wire through those contacts, again no need to disconnect them, to read the resistance on your meter connected to the dryer wire. If you see resistance in the wire now, then you know that the relay was probably not closing.

You can check the heat selector switch and the timer in exactly the same way. If at this point you still don't read the resistance on your meter, it's time to throw in the towel and call a professional appliance service technician. The reason to call a professional right now is that electronic control boards and timers are very expensive. If you guess what the problem is, and you're wrong, you won't pay for that item. This is because electronic control boards and timers cannot be returned. One more thing, for the record, appliance service technicians don't like working on appliances that have been taken apart by an inexperienced person. Be sure to reassemble the dryer before calling a dryer technician. This will save you the expense of having to put it back together for yourself. These are steps for Washing Machine Repair.