F21
Whirlpool Dishwasher
Severity: MinorWhat Does This Error Mean?
Whirlpool dishwasher error F21 means the rinse aid dispenser or its sensor has a fault. The dishwasher uses rinse aid to help water sheet off dishes during drying, preventing spots and streaks. F21 often means the rinse aid reservoir is empty, the dispenser is clogged, or the sensor has failed.
Affected Models
- Whirlpool WDT750SAHZ
- Whirlpool WDT970SAHZ
- Whirlpool WDTA50SAHZ
- Whirlpool WDF520PADM
- Whirlpool WDT730PAHZ
Common Causes
- The rinse aid reservoir is empty and needs to be refilled
- The rinse aid dispenser opening is blocked by dried rinse aid or detergent residue
- The dispenser flap or door is stuck in the closed position and will not open during the rinse cycle
- The rinse aid level sensor is coated with residue and is giving an inaccurate reading
- The rinse aid dispenser solenoid has failed and cannot open the dispenser door during the cycle
How to Fix It
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Open the dishwasher door. The rinse aid dispenser is on the inside of the door, next to the detergent dispenser. Turn the cap counter-clockwise and lift it off.
The dispenser cap is usually marked with a rinse aid symbol — a star or a droplet icon.
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Check the level. If it is empty or very low, refill with liquid rinse aid up to the maximum fill line. Replace the cap and press it down firmly until it clicks.
Do not overfill — overfilling causes rinse aid to spill into the tub during washing, which creates excessive foam.
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Wipe around the inside of the dispenser opening with a damp cloth to remove any dried rinse aid or detergent residue that may be blocking the sensor.
A toothpick can help clear debris from the small sensor opening inside the dispenser compartment — do this gently.
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Check the dispenser flap — the small door that opens to release rinse aid during the rinse cycle. It should move freely when pressed with your finger. If it feels sticky or stiff, clean around it with warm water.
Dried rinse aid can cause the dispenser flap to stick, preventing it from opening during the cycle.
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Run a complete wash cycle and observe whether F21 clears. If the error persists with a full dispenser and a clean sensor, the dispenser assembly likely needs replacement.
A replacement rinse aid dispenser assembly for Whirlpool dishwashers typically costs $20–$50 in parts.
When to Call a Professional
If refilling and cleaning the dispenser does not fix F21, the dispenser solenoid or level sensor needs professional testing. A technician can replace the dispenser assembly — it is typically a moderate-cost part and straightforward to fit.
Frequently Asked Questions
Can I run the dishwasher without rinse aid?
Yes, the dishwasher will still wash dishes without rinse aid. However, dishes — especially glassware — will have more water spots and streaks, and drying performance will be worse. In hard water areas, skipping rinse aid also accelerates limescale buildup inside the machine.
My rinse aid reservoir is full but F21 is still showing. Why?
If the reservoir is full but the error persists, the level sensor is likely coated with residue and is giving a false empty reading. Clean around the sensor inside the dispenser compartment. If that does not help, the sensor or dispenser solenoid has likely failed and needs replacing.
How often should I refill rinse aid?
For most households running the dishwasher daily, refilling rinse aid once a month is typical. The built-in rinse aid indicator light will tell you when it is running low — watch for it on the control panel. Adjusting the rinse aid dosage setting (if your model has one) to match your water hardness helps it last longer.