Dishwashers clean by hydraulic reaction: water forced out of angled jets pushes the arm round, and the sweeping jets do all the work. If an arm does not turn, the machine is effectively spraying two fixed points and everything else comes out dirty. There is no motor driving the arm, which is good news — the fault is always either something blocking it, something clogging it, or not enough water pressure reaching it.
Read this first
- Switch the dishwasher off at the breaker before removing the sump cover or reaching into the pump area.
- Broken glass hides in dishwasher sumps and in spray arm ends. Use a flashlight and gloves rather than bare fingers.
- Never defeat the door latch to run a cycle with the door open so you can watch the arms — you will flood the kitchen and the interlock exists for a reason.
Step by step
Spin both arms by hand
Open the door and give the lower arm and the upper arm a flick with a finger. Each should spin several full turns freely and coast to a stop, with no grinding, wobble or catching. An arm that will not turn at all, or turns with a gritty resistance, has a bearing or debris problem. An arm that spins beautifully by hand but still does not turn during a cycle has a water supply problem instead — that distinction decides everything below.
Look for what the arm is hitting
Load the machine the way you normally do, then close the door slowly while watching, or spin each arm by hand with the racks in place and listen for a clunk. Long knives poking through the cutlery basket, tall stemware, a pot handle hanging down from the upper rack, and the lip of a large mixing bowl all catch the arm as it swings. A sagging upper rack that has dropped on one side does exactly the same thing.
Clear every jet
Twist or unscrew the arm off — most release with a quarter turn or a single central nut — and hold it up to the light. Every hole should be open. Work a straightened paperclip through each blocked one, paying attention to the small angled jets at the ends of the arm, which do most of the driving. Then flush the arm out under a hot tap from the underside so the debris exits the way it came in rather than being pushed deeper.
Clean the filter and the sump
Twist out the cylindrical filter assembly in the tub floor and lift the flat screen underneath it. Wash both under hot running water with a brush. Then look into the sump with a flashlight and remove labels, seeds, fruit stickers, bits of bone and glass. A clogged filter starves the circulation pump, and a starved pump cannot generate the pressure the arms need to turn — this is the most common cause of arms that spin fine by hand and not at all in service.
Check the arm's bearing and retaining nut
Look at the hub the arm rotates on. On lower arms it is usually a plastic post with a shoulder; on upper arms it is often a nut through the centre. Wear, a cracked hub, or a retaining nut that has been overtightened will bind the arm. Check for a hairline crack on the underside of the arm too — a cracked arm loses pressure through the split and stops driving itself round. Arms are typically $15 to $40 and simply twist on.
Check the upper feed tube
Water reaches the upper arm through a tube that runs up the back of the tub, or in some designs through a fitting on the upper rack itself. Check that the tube is clipped in place, is not split or disconnected at either end, and that the rack-mounted coupling on models that use one is seated. A machine where the lower arm turns strongly and the upper does nothing almost always has a feed tube problem rather than an arm problem.
Mark the arm and run a real cycle
This is the honest test. Stick a small piece of masking tape on the tub edge, position the arm pointing at it, close the door and run a short cycle without opening it. When it ends, look at where the arm sits. If it has moved, it turned. If it is exactly where you left it, it never rotated, and you have confirmation rather than guesswork. Do the same for the upper arm separately.
What this repair costs
Doing it yourself
$0–$60
Hiring a technician
$140–$350
Prices are general estimates for typical US jobs, not quotes. What you actually pay depends on your appliance's brand and age, the part required, your region, and each shop's labour rate. The DIY figure assumes you supply the labour and buy the part yourself.
Parts you may end up buying
| Part | Install | Typical price | Typical lifespan |
|---|---|---|---|
| Spray Arm | easy | $15–$40 | 5–8 years |
| Inlet Valve | moderate | $15–$40 | 8–12 years |
| Drain Pump | moderate | $35–$120 | 8–12 years |
| Door Latch and Switch Assembly | easy | $20–$80 | 6–12 years |
| Heating Element | moderate | $25–$85 | 8–14 years |
| Float Switch | easy | $10–$35 | 10+ years |
| Door Gasket | easy | $20–$75 | 6–12 years |
| Rack Roller and Adjuster Kit | easy | $12–$50 | 5–10 years |
| Detergent Dispenser | moderate | $30–$100 | 8–12 years |
| Circulation Pump and Motor | advanced | $90–$330 | 8–14 years |
Still not fixed
When to call a pro
If both arms are clear, the filter is clean, the machine fills normally and the arms still will not turn, the circulation pump is not generating pressure — either the impeller is damaged or the pump motor is failing. That is a $90–$330 part and often means pulling the machine out and laying it on its back, which crosses into a reasonable service call. On an older machine, weigh that repair against the cost of a new dishwasher before committing. Any hardwired work under the machine needs the circuit confirmed dead.
More dishwasher guides
- Dishwasher Not Cleaning — Find Out What It Is Short Of30–60 minutes
- Dishwasher Not Draining — Clear the Standing Water20–60 minutes
- Dishwasher Leaking — Find the Source Before It Damages the Floor30–90 minutes
- Dishwasher Not Drying Dishes — Why, and What Actually Helps15–45 minutes
- Dishwasher Soap Dispenser Not Opening — Why the Pod Is Still There20–60 minutes
- Dishwasher Door Won't Latch or Stay Closed30–90 minutes
- Dishwasher Won't Start — Work Through the Lockouts First30–75 minutes
- Dishwasher Not Filling With Water — Trace the Supply45–90 minutes
- Dishwasher Smells Bad — Clear the Sources in Order45–90 minutes plus a cleaning cycle
- White Film on Dishes — Hard Water Scale or Permanent Etching?30 minutes plus a test cycle
- Dishwasher Making Noise — Match the Sound to the Part30–75 minutes