Dryer Timer Not Working

Before we begin talking about a dryer timer that is not advancing, or otherwise not working, let's first talk about what a dryer timer is. Today dryer manufacturers are starting to switch over from timers, to dryer electronic controls. Electronic controls are less expensive to manufacture, and for the most part more dependable than a dryer timer. That's because dryer timers are mechanical. Of course anything mechanical will eventually fail. A dryer timer is usually made up of a metal housing, with a small motor secured to the outside of the housing. The motor is connected to a series of gears, that rotate cams, that open and close switch contacts within the timer. Imagine for a second that a dryer console had a series of push-button switches running from left to right. Now imagine that these push-button switches controlled the loads on the dryer. One switch controls the motor, another switch controls the heater, and so forth. If you were to walk up to this imaginary dryer and push the switch that controls the motor, the motor would start, and the dryer drum would rotate. And if you had clothes in the dryer, you could push the next switch that completed the circuit to the dryer heater. Now you have a dryer that is tumbling the clothes with the heater on.

We all know that taking clothing out of a hot dryer before it has time to cool down, will cause the clothes to wrinkle. So using our imaginary dryer, you would have to set the timer on your wristwatch or cell phone, to estimate when the clothes were dry. This way you could put your beer down, put the football game on pause, and run back to the dryer and push the switch that would turn the heat off. The drum would continue to rotate, because the switch for the motor was still depressed. After 15 minutes or so, you could return to the dryer, and depress the switch to disengage the contacts for the motor, the dryer would shut down, and now you could remove the clothing that is dry and cooled down.

Fortunately, dryer timers have motors on them, and a series of gears and switches that control the motor and the heater, permitting you to enjoy your beer and football without all that unnecessary exercise. During the dryer design process, the engineers decide how long a set of switch contacts inside a dryer timer should be closed, to control specific loads. The manufacturer of the timer uses this information to manufacture the gears and cams within the timer to accommodate that time frame.

The good news is, dryer timers rarely fail. In fact, probably 60% of dryer timers purchased are unnecessary. That's because a dryer timer is the most misdiagnosed component on a dryer. The interesting thing about that is, most appliance parts sales outlets, do not allow the return of timers that have been installed. Therefore if you misdiagnosed the problem and assume it is the dryer timer, it is yours to keep.

here are basically two things that will make a dryer timer not advance. One is a motor or mechanical failure within the gears of the timer, the other is when the timer is used on the automatic cycle of the dryer. Most dryers that have an automatic cycle, use the dryer thermostat to control when the timer can advance toward the off position. Therefore if the dryer control thermostat is not cycling on and off, the dryer timer will not advance, and you might think that the timer is defective when it is not. When you have a timer that is not advancing, always rotate the timer to the position that operates by time. In other words, set the timer for 60 minutes drying time. If the timer starts to advance after a few minutes, it's probably not defective. If you have a dryer timer that is not advancing in the automatic cycle, you need to look for a defective control thermostat, or a vent restriction. If the vent is restricted on a dryer, and by the way this is very very common, the control thermostat can not cycle because the hot air is not moving past it. The heater will then cycle on the high limit thermostat. However in most cases, this will not advance the timer motor.

So how do you diagnose a defective timer on a dryer that is not heating? Assuming that you have checked all components in the heat circuit before the timer, now you want to see if the timer switch contacts that control the heater are defective. The first thing that you need to do is identify what switch contacts those are. To do that you will have to look at the timer sequence chart, or dryer schematic, the owners or service manual. If you have followed the diagnostic procedures that we have listed for a dryer that is not heating, you will be at a point where you have your ohmmeter on the dryer cord. If you need more information about a dryer that's not heating, and how to put your meter on the dryer cord to check it, Click Here. Assuming that your meter is on the dryer cord at this point, and that you have identified the particular switch contacts to control heat in the dryer, all you need to do is use a jumper wire across those contacts. If the wires on your timer are attached to individual spade terminals, you can look for the heavy-duty wires. If the wires are attached to your timer by a plastic connector block, meaning when you unplug the wires you unplug them all at once, it will be more difficult to jump out the heater switch contacts. What makes it so difficult is the fact that you need to leave the wire connectors attached to the dryer timer. This is where that extra set of leads for your meter comes in handy. You can slide the long metal ends of the extra meter leads alongside the wires that go in the connector block. Now you will have two meter leads sticking out of the plastic block, but not attached to a meter. You can attach your jumper wire with alligator clips on the other end of those leads, the portion of the leads that normally go into the voltmeter. Don't forget that you will have to move the slide on the motor shaft that controls the weights for the centrifugal switch. This will ensure that the motor centrifugal switch contacts that control the heater are closed.

To back up your diagnosis, when you read the resistance of the heater on your meter, remove one of the wires that normally supplies power to the heater. When you do that, the meter should stop reading the heater resistance, and go back to blinking indicating infinite resistance.