Appliance controls are parts of things. Because they are parts of dozens of things in your home, knowing how to fix them is vital to fixing many things you own. (You can order replacement parts from FixItClubParts.com.) This Fix-It Guide on appliance controls repair tells how appliance controls work, what often goes wrong, how to identify an appliance controls problem, and what parts and tools you will need to fix it. It then gives instructions for how to test and service an appliance controls switch, how to test and service an appliance controls thermostat, how to test an appliance controls rheostat, how to test an appliance controls timing mechanism, how to test an appliance controls timer motor, and how to test and service an electronic appliance controls touch-pad. Appliance controls repair may be all that is need to complete power tool repair, range hood repair, roasting oven repair, sump pump repair, and many other household repairs.
How Do Appliance Controls Work?
Appliance controls are the devices that turn things on and off, regulate temperature, speed, duration, and otherwise control appliance functions. Appliance controls include switches, thermostats, rheostats, and timing mechanisms. Some appliances, such as toasters, use mechanical controls while others, like microwave ovens, use digital controls. Knowing how they work will help you fix just about any of them.
Appliance switches vary in complexity and functions. Switches operate by making contact with the conductor of an electrical circuit. When an appliance is plugged in, it’s connected to an electrical circuit in your home. Power runs through the wires of the circuit to the appliance. When the appliance’s on-off switch is turned on, electricity flows through the switch to operate the appliance. There are several common types of switches: push-button, toggle, rocker, slide, and throw switch.
Other appliance controls are also switches. Rheostats, thermostats, solenoids, and timers, for example, are all types of switches. These components operate inside appliances to turn on motors, open and close valves, control heating elements, and turn on different parts of the appliance during different cycles, such as the rinse and spin cycles of a washing machine. Let’s take a closer look at them.
A thermostat is a switch that controls temperature in a heating element or a cooling device. It opens and closes a circuit to furnish current based on temperature. Thermostats used in appliances may use a bimetal strip, bimetal thermodiscs, or a gas-filled bellows chamber to control the electrical contact. If faulty, they should be replaced rather than repaired.
A rheostat is a variable controller that directs the amount of current flowing to many older appliance components. A blender with a dial control that can be turned to increase or decrease motor speed uses a rheostat to do so. Because rheostats can be damaged by moisture, they can easily malfunction.
A timing mechanism controls current flow based on a mechanical or digital timing device similar to a clock. Timing mechanisms on small appliances usually turn the appliance on or off. Timers on major appliances–washing machine, dishwasher, dryer, frost-free refrigerator, or oven, for example–control the various cycles. Mechanical timers on large appliances consist of a shaft, gears, and a series of notched cams, one for each circuit or cycle. The timer is powered by a small timer motor. Digital timers are much simpler, using low-voltage electricity to control various functions such as turning on or off a device. While some timing mechanisms can be adjusted, those that are faulty should be replaced rather than repaired.
Many of these mechanical controls have been replaced, or at least are assisted, by digital controls. The good news is that digital controls are relatively trouble free, going many years without service. The bad news is that when they do go out, there’s no repair to do; you simply buy another unit and plug it in exactly as the old one. Of course, make sure you’ve solved any other electrical problems first so the digital controller won’t be damaged on installation.
What Can Go Wrong with Appliance Controls?
What can go wrong with appliance controls? They can quit controlling! Switches won’t turn on and off, thermostats don’t properly regulate heat, rheostats don’t provide smooth control, and timers quit timing. In many cases, all that’s needed is a good cleaning or reconnecting the wires. Otherwise, the controller should be replaced rather than repaired.
Sometimes the only problem with a controller is that an electrical connection to or from it has become loose. With the appliance unplugged, carefully wiggle the connection to make sure that it fits snugly. If there is corrosion at the terminal, remove the connection and clean the terminal with a small brush.
How Can I Identify an Appliance Controls Problem?
- If an appliance won’t operate at all, test the on-off switch (see below) and replace if faulty. Also check the thermal fuse.
- If an appliance doesn’t heat, test the thermostat (see below) or rheostat (see below) and replace if faulty.
- If an appliance doesn’t come on at the set time, or if the machine doesn’t change functions as designed, test the timer (see below) and replace it if it is faulty. It’s usually more efficient to replace a faulty appliance control than to attempt repair. Some devices, such as heating pads, require replacement of the entire unit.
What Do I Need for Appliance Controls Repair?
Appliance controls typically are replaced, not repaired. In some cases, they may just need a careful cleaning of contacts. Otherwise, get replacement parts from the manufacturer or aftermarket supplier. Here’s what you’ll need:
- Small file for cleaning contacts
- Electrical contact cleaner
What Are the Steps to Appliance Controls Repair?
Test and service an appliance switch:
- Unplug the appliance and disassemble enough to access the switch. Disconnect one lead from the switch.
- Set the multimeter on RX1 (resistance times 1) scale. Clip probes to the switch terminals or leads. Turn the switch on (for multi-speed switches, press one switch at a time and note each reading). Zero ohms means the switch is okay. High or fluctuating ohms means the switch is broken or dirty.
- Clean any switch contacts with a small file or with electrical contact cleaner. Contacts should make firm connection when the switch is on. If they don’t, replace the switch rather than repair it.
- Use electrical contact cleaner to clean less accessible switch contacts. In order to work cleaner into the switch, operate the control buttons as you spray the cleaner into apertures. Don’t over-spray.
Test and service a large-appliance thermostat:
- Unplug and disassemble the appliance enough to access the thermostat.
- Hook the clip of the multimeter to one lead of the thermostat and touch the probe to the other. Or you can touch one probe of the multimeter to each terminal. The reading should be zero.
- Turn down the temperature control dial; you’ll see the contact points open at the thermostat. The meter should stop buzzing when the contacts open.
- If the thermostat is faulty, replace it with a new one, following the manufacturer’s instructions.
Test and service a small-appliance thermostat:
- Unplug and disassemble the appliance enough to access the thermostat.
- Set the multimeter on RX1 (resistance times 1) scale. Place one probe of the multimeter on the output side and one probe on the input side. The reading should be zero.
- Replace the thermostat if faulty.
Test an appliance controls rheostat:
- Unplug the appliance and disassemble enough to access the rheostat.
- Set the multimeter on RX1 (resistance times 1) scale. Clip the probes to the rheostat terminals or leads. Zero ohms means the rheostat is okay. As the probes are moved along the rheostat wire, the reading should change incrementally.
- If necessary, use canned (compressed) air to clean around a rheostat wire.
Test an appliance controls timing mechanism:
- Unplug the appliance and access the timing mechanism.
- Set the multimeter to RX1 (resistance times 1) scale. Make a sketch of the timer wires for future reference, then disconnect all timer wires from their terminals. Make sure you’ll be able to reconnect the wires exactly the same way when you’re done.
- Touch or clip one probe of the meter to the common terminal. Touch the other probe to each cycle terminal in turn. Rotate the timer control knob as you work. The multimeter should read zero ohms meaning there’s no resistance to the flow of electricity.
- If one or more circuits do not give these results, the timer is faulty and should be replaced.
- To replace a timer, disconnect its wires one at a time, connecting the corresponding wires of the new timer as you progress in order to avoid the chance of mis-connection.
Test an appliance controls timer motor:
- Unplug and disassemble the appliance enough to access the timer motor .
- Set the multimeter on the RX10 scale and connect the leads to the two motor wires. A good motor should give a relatively high reading (usually 2,000 to 3,000 ohms), but not infinite (meaning no electricity will flow through it).
- If the reading is infinity, replace the motor or the entire timer mechanism, as available.
Test and service an electronic appliance controls touch-pad:
- If the entire pad does not work, check the circuit board or pad wiring on the rear of the pad for incomplete connections.
- If a single button does not work, clean its contacts by rubbing them gently with a pencil eraser and then wiping away any residue with a foam swab dipped in alcohol.
- If the pad still does not work, replace the entire assembly.
Many digital control systems include error codes that can tell you what the problem is. The appliance’s owner’s manual or a helpful parts supplier can help you find and interpret the codes.