Reading A Wiring Diagram For Appliance Repair

A wiring diagram is a drawing of the electrical circuit of whatever it is you are working on. Often when working on appliances, it is necessary to read these diagrams when there is an electrical problem with the appliance you are working on. Knowing how to read a wiring diagram can save you from buying parts you don’t need.

Every appliance comes with a diagram hidden on it somewhere such as under the bottom, in the control panel behind the storage drawer or taped to the back. It will be somewhere you will not find it unless you were looking for it.



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On this page I will explain the basics on how to read a wiring diagram. The type of diagram I will talk about is a ladder diagram because it is easy to read and is the most common type of diagram. A ladder diagram looks like a ladder just as the name suggests.

So if you have an electrical device that will not work, look at the diagram and find the device. Everything between the two main lines that the light is on can affect the light. Also you should know that the main lines are marked L1, L2 and N. If a diagram has just L1 and N then the circuit is 110V, if the diagram has L1 and L2 then it is a 240 circuit and if it has L1, L2 and N it is a 110-220V circuit. Below is a picture of a few simple ladder-wiring diagrams to help explain what I am talking about.

110V Light Circuit

This first diagram is two very simple light circuits. From looking at this diagram you should see that both lights run all the time because there isn’t a switch to control them or a fuse. Also note that both lights run off of 110V because they are connected between the L and the N.

110V Light Circuit With Switch And Fuse

The next diagram is the same diagram only this time I stuck in a switch and a fuse. You should notice that the fuse cuts both lights off and the switch only turns off the top light. So the other light stays on all the time, provided the fuse is not blown.

220V Light Circuit

This diagram is the same as the first one only this time you should notice that the lights run off of 240V because the circuit is connected between a L1 and L2 lines.

110-220V Circuit

This diagram is a 110-220V circuit. There is a light that runs off of 110V and is controlled by a switch. There is a heater that runs off of 220V and is controlled by a switch and a thermostat. There is a fuse that turns both the heater and the light off if it is blown.

Simple Dryer Circuit

This is a simple dryer wiring diagram that shows examples of most of what you will see on many other wiring diagrams. I will break it down and explain each component of the dryer and how it is controlled.



The Motor

The motor is the most complicated part of this diagram. Notice that the motor coils are connected to an internal motor switch, which is only closed if the motor is running. This is why there is a start switch; the start switch temporary bypasses the motor switch to allow the motor to run. Once the motor starts, you no longer need the start switch because the motor switch takes over so the start switch is only closed when you are pressing on it.

There is also a timer switch and a door switch that have got to be closed in order for the motor to run. So when the timer is on, the door is closed and the start switch is pressed, the motor will start. It runs off of 110V.

The heater

A timer switch, two thermostats and the motor switch control the heater. The motor switch will only close if the motor is running. One of the thermostats is for turning the heater on and off during normal operation. The other thermostat is for safety and will turn the heater off if it overheats. The timer switch is on when the timer is on and calling for heat. It runs off of 220V.



The timer

The timer motor runs until the timer switch turns it off and it stays off until someone comes and turns it on. This means that the timer turns off when it gets to a point. It runs off of 110V.



The light

The light is on when the door is open so that you can see inside the drum. It runs off of 110V.



The safety switch

The safety switch is a switch that cuts the entire dryer off if it overheats.

Note that this is not an actual dryer wiring diagram, it is just a sample I drew to help you understand wiring diagrams.

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Shawn

  • Appliance repair since 1996
  • 2-years refrigeration courses
  • 1-year electric theory courses
  • 1-year residential wiring course


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