Short answer: A control board is usually the problem only after the cheaper parts check out. Confirm the appliance has power, look up any error code, and test the door or lid switch, fuses, and sensors. Then inspect the board for burn marks, swollen capacitors, or corrosion. If everything else tests good and the symptoms still point to the board, match the part number printed on the board itself and replace it.
The control board is the brain of a modern washer, dryer, refrigerator, dishwasher, or range. When it fails, the appliance can go completely dead, ignore button presses, or stop halfway through a cycle. The trouble is that an inexpensive door switch or a blown thermal fuse can cause the exact same symptoms.
Because a board usually costs more than the parts around it, it pays to rule those parts out first. This guide walks through the checks in order, shows you how to read the label on a board, and explains why some replacement boards fail right after they're installed.
Safety before you open anything
- Cut the power. Unplug the appliance or switch off its breaker before removing any panel. Turning the appliance off at the controls is not enough.
- Shut off gas and water where it applies. Close the gas valve before moving a gas range or dryer, and the water supply before working on a washer, dishwasher, or refrigerator with an ice maker.
- Leave microwave internals to a trained technician. A microwave's high-voltage capacitor can hold a dangerous charge even after the unit is unplugged.
- Protect the board from static. Wear an anti-static wrist strap if you have one, or touch a grounded metal object before handling the board. Hold it by the edges.
- Know when to stop. Some of the checks below involve a multimeter. If you aren't comfortable testing voltage, test only with the power off, or call a technician or electrician for that step.
Main board or user interface board?
Many appliances have two boards, and it helps to know which one you're dealing with.
- The main board (also called the power board, relay board, or machine control) switches power to the motors, heaters, pumps, valves, and compressor. It is often mounted in the console, under the top, behind the back panel, or near the bottom of the cabinet.
- The user interface board handles the buttons, knobs, and display. It sits directly behind the control panel.
A simple rule of thumb: if the display and buttons work but the appliance won't run a component, look toward the main board and the parts it controls. If the appliance seems to run but the display is blank, garbled, or unresponsive, look toward the user interface board and its ribbon cable.
Common symptoms and what to check first
| Symptom | Check these first | Points to the board when |
|---|---|---|
| Completely dead, no lights | Breaker, outlet, power cord, door or lid switch, any fuse on the board | Power reaches the board, the fuse is good, and nothing lights up |
| Lights come on but it won't start | Door switch, lid lock, door lock assembly, thermal fuse | The switches test good but the board never sends power to the motor |
| Dryer runs but won't heat | Thermal fuse, heating element or gas igniter, thermostats, one tripped side of a 240V breaker | On electronic models, the heater circuit tests good but the board's heat relay never closes |
| Refrigerator warm, fans or compressor not running | Condenser coils, condenser and evaporator fans, defrost heater and thermostat, start relay, thermistors | Those parts test good and the board isn't supplying voltage to them |
| Buttons don't respond or display is garbled | Keypad membrane, ribbon cable seated fully, moisture behind the panel | The cable and keypad are good, which points to the user interface board |
| Stops mid-cycle or resets randomly | Loose or corroded connectors, a leak dripping onto the board, an overheating motor or pump | The problem continues after connectors are cleaned, reseated, and dry |
| Error code on the display | The part the code names, according to the tech sheet | The code specifically calls out the board or a communication fault, or the named part tests good |
Step-by-step: rule out the cheaper parts first
1. Confirm the appliance is getting power
Check the breaker panel and reset anything that has tripped. Plug a lamp or phone charger into the same outlet to confirm it works. Dryers and ranges run on 240 volts through a double breaker, and if only one side trips, the appliance may light up and even run without heating. Resetting the breaker fully (off, then on) is worth doing before anything else.
2. Read the error code and find the tech sheet
If the display shows a code, look it up before you touch a single part. Most appliances have a folded tech sheet tucked inside, often behind the kick plate, inside the console, under the cooktop, or on the back of a panel. It lists what each code means and usually explains how to run a diagnostic or service mode that tests components one at a time.
3. Test the usual suspects
With the power off, use a multimeter to check the inexpensive parts that most often mimic a board failure:
- Door switches, lid switches, and door locks should show continuity when the door is closed or the switch is pressed.
- Thermal fuses in dryers and some dishwashers should show continuity. A blown one can cause no heat or no start, depending on the model.
- Sensors and thermistors should read within the resistance range listed on the tech sheet for the current temperature.
- Wire connectors should be fully seated, with no melted plastic, green corrosion, or darkened pins.
4. Inspect the board
Take a photo of every connector before you unplug anything, so reassembly is easy. Remove the board and look closely under good light, front and back. Warning signs include:
- Brown or black scorch marks, especially around relays and connectors
- Capacitors with domed tops or crusty residue around their base
- Cracked solder joints, often a thin ring around a pin
- White or green corrosion from water or condensation
- A burnt electrical smell
5. Make the call
If the board shows clear damage, it needs replacing. If there's no visible damage but power, codes, and the cheaper parts all check out, the board is still the most likely cause. Boards can fail internally without leaving a mark.
Why some replacement boards fail right away
A board rarely burns out for no reason. A relay on the board switches power to a motor, pump, or heater, and if that component has shorted, it can pull enough current to damage the relay. Install a new board without fixing the shorted part, and the new board can fail the same way.
Before you install a replacement, look at what the damaged area of the old board controls. If the scorch mark sits next to the relay for the drain pump, test the drain pump. Also fix any leak that let water reach the board, and replace any connector with melted or discolored pins, since a bad connection can overheat the new board's terminals.
How to match a replacement control board
Control boards are one of the easiest parts to order wrong, because similar-looking boards can differ in firmware, connectors, or the models they support. Before you order:
- Start with your appliance model number. If you don't have it yet, see where to find your appliance model number.
- Use the part number printed on the board. Boards often carry more than one number, so match the service part number rather than a random number stamped on the circuit board.
- Check the revision or suffix. The letters or digits after the main number can indicate a newer version. A newer revision often replaces an older one, but confirm it before ordering.
- Note any software or version code. Some brands program boards for specific models. If your old board lists a version, compare it with the listing or ask the seller.
- Compare connectors. Count the connectors on your old board and note their positions. A board with a different connector layout won't fit, whatever the label says.
- Take photos of both sides. Clear photos of the label and the connectors make it much easier for a parts seller to confirm the match.
New, used, or rebuilt: which board should you buy?
You'll usually have three options, and each has trade-offs.
- New OEM boards come straight from the manufacturer's parts network. They cost the most and are only available while the manufacturer still supports the part.
- Used OEM boards are genuine boards removed from other appliances. They usually cost much less, and once a manufacturer stops making a board, they're often the only option left for an older appliance. Check the photos, confirm an exact part number match, and read the seller's return and warranty terms.
- Rebuilt or repaired boards are original boards with failed components replaced. Quality depends heavily on who did the repair.
Whichever route you choose, compare the price of the board with the age and value of the appliance. A common rule of thumb in appliance repair is to think twice about any repair that costs more than half the price of a comparable new appliance.
Rabon Services Group carries thousands of control boards for refrigerators, ranges, washers, and dryers. Search by the number printed on your board using our part number search, and review our refund policy before you order.
Installing the new board
With the power still off, ground yourself, handle the new board by its edges, and connect each harness using the photos you took earlier. Press every connector until it seats fully. Reinstall the board and panels, restore power, and run a diagnostic or test cycle if your tech sheet describes one. For a detailed walkthrough on one common appliance, see our guide on how to replace a dryer control board.
Frequently asked questions
What causes an appliance control board to go bad?
The most common causes are a shorted component such as a motor, pump, or heater overloading a relay; water or condensation reaching the board; power surges; loose connectors that overheat; and ordinary age and heat over many years of use.
Can a control board be repaired instead of replaced?
Sometimes. Someone with soldering experience can replace a failed relay or swollen capacitor. For most DIYers, replacing the whole board is faster and more reliable, especially when the damage has spread across the circuit.
Do I need to program a new control board?
Many boards work as soon as they're installed. Some brands, though, ship boards that have to be set up for a specific model, or require a matching software version. Check the part listing, the installation instructions, and the tech sheet before you install.
How do I know if it's the main board or the display board?
If the buttons and display respond normally but a motor, heater, or pump never turns on, suspect the main board or that component. If the appliance runs but the display is blank or buttons don't register, suspect the user interface board and its ribbon cable.
Is a used control board a safe buy?
A used OEM board can be a smart way to save money or keep an older appliance running, as long as the part number matches exactly and the seller stands behind the part. Check photos for burn marks or corrosion and read the return terms before you order.
Written by the Rabon Services Group team in Farmington, Minnesota. Since 2017, we've helped DIYers, repair shops, and extended warranty companies find the parts they need to repair appliances.