Dishwasher Not Cleaning Dishes? 6 Things to Check Right Now
A dishwasher that runs a full cycle and still leaves food residue, cloudy glasses, or greasy film on your plates isn’t just annoying — it’s a sign something mechanical or maintenance-related has gone wrong. Before assuming you need dishwasher repairs, there are several things worth checking yourself. Some of these you can resolve in under ten minutes. Others will point you toward a specific component failure that needs professional attention. This guide covers the most common causes across all major brands — Bosch, Miele, Samsung, LG, Whirlpool, GE, and others — so you know exactly what you’re dealing with.
1. Clogged or Damaged Spray Arms
The spray arms are the workhorses of your dishwasher. They spin and push pressurized water through small nozzles to reach every corner of the tub. When those nozzles clog with mineral deposits, food debris, or broken glass particles, water distribution becomes uneven — and the bottom rack or upper rack (depending on which arm is affected) stops cleaning properly.
Remove the spray arms — most twist off or unclip without tools — and hold them up to light. If any of the holes are blocked, soak the arms in warm white vinegar for 20–30 minutes and use a toothpick or thin wire to clear each opening. On Bosch 300 and 500 series dishwashers, a third spray arm sits beneath the upper rack; this one is frequently overlooked and is a common culprit in top-rack cleaning failures. Miele dishwashers use a slightly different arm design with a central water feed — if the connection seal is worn, pressure drops significantly even when the holes themselves are clear.
Also check that the arms spin freely when you rotate them by hand. A spray arm that catches on a tall utensil or oversized pan won’t complete its rotation cycle.
2. Blocked or Dirty Filter Assembly
Most modern dishwashers — including virtually every Bosch, Miele, Fisher & Paykel, and LG model made in the last decade — use a manual filter system rather than a self-cleaning grinder. That filter sits at the bottom of the tub and needs to be cleaned every two to four weeks depending on how heavily the machine is used.
Twist out the cylindrical filter and lift out the flat mesh screen beneath it. Rinse both under running water and use a soft brush to remove any greasy buildup. A filter clogged with food particles forces the pump to recirculate dirty water, which means your dishes are technically being washed in the same contaminated water the entire cycle. This is one of the most common reasons Ottawa households report that their dishwasher “stopped working as well as it used to.”
3. Dishwasher Repairs Often Trace Back to the Wash Pump or Circulation Pump
If the spray arms are clean, the filter is clear, and you’re still getting poor cleaning results, the problem may be internal. The circulation pump forces water through the spray arms under pressure. When the pump impeller wears down or a bearing starts to fail, water pressure drops noticeably — dishes come out wet but not clean, and you may hear a low humming or grinding sound during the wash cycle.
On Samsung dishwashers, error codes like 5C, 5E, or OC can indicate drainage or circulation issues that affect wash performance. LG models may display AE or IE errors that point to water supply or pump faults. Whirlpool and Maytag machines typically don’t throw a code for a weakening pump — the only symptom is progressively worse cleaning results over weeks or months.
This type of repair requires disassembling the pump housing and is not a DIY-friendly job on most platforms.
4. Water Temperature and Detergent Problems
Dishwasher detergent — whether pods, powder, or gel — requires water temperature of at least 49°C (120°F) to activate enzymes and cut through grease effectively. If your home’s hot water heater is set low, or if the dishwasher is on a long supply run from the heater (common in larger homes in Nepean and Barrhaven), the water arriving at the machine can be too cool for proper cleaning.
Run the hot water at your kitchen sink for 30–45 seconds before starting a cycle. This purges the cold water sitting in the supply line and ensures the dishwasher fills with genuinely hot water from the first minute. Many Bosch dishwashers include an internal heating element and an Aqua-Stop sensor that monitors incoming water temperature — if the supply temp is consistently low, these machines compensate but extend cycle time significantly.
Also check that you’re not overloading the detergent dispenser or using old detergent. Pods that have absorbed moisture or powder that has clumped won’t dissolve correctly, leaving residue on dishes and the tub interior.
5. Loading Errors and Blocked Detergent Dispenser
Even a perfectly functioning dishwasher can’t clean dishes that are loaded incorrectly. Nesting bowls, stacked plates with no gap between them, and large cutting boards placed flat across the lower rack all block water circulation and prevent spray arms from rotating freely.
Equally important: make sure nothing is blocking the detergent dispenser door. A large pot or pan positioned directly in front of the dispenser will prevent it from opening during the wash cycle — detergent stays trapped inside, and dishes go through the entire cycle without any cleaning agent. This is a surprisingly common issue and one that’s easy to fix before assuming you need a repair.
Frequently Asked Questions
Why are my dishes coming out with a white film even after a full cycle?
White residue is almost always caused by hard water mineral deposits — calcium and magnesium that precipitate out of the water during the heated dry cycle. Ottawa’s water supply has moderate hardness levels that can cause this over time. Using a rinse aid consistently, running a monthly dishwasher cleaning cycle with citric acid or a commercial cleaner, and verifying that your detergent contains a water-softening agent will usually resolve this. On Miele and Bosch dishwashers with built-in water softeners, check that the salt reservoir is filled — an empty softener reservoir is a direct cause of filming on glassware.
My dishwasher is running but the dishes on the top rack aren’t getting clean. What’s causing that?
Top-rack cleaning failures almost always point to either a clogged upper spray arm, a worn-out upper rack spray arm seal, or insufficient water pressure reaching the second level of the machine. On Bosch dishwashers specifically, the middle spray arm that feeds the upper rack connects via a tower in the back wall of the tub — if that connection fitting cracks or the seal degrades, pressure to the top rack drops significantly. Checking that fitting is a good first diagnostic step before looking at the pump.
How do I know if my dishwasher problem needs a technician or if I can fix it myself?
Filter cleaning, spray arm clearing, and loading adjustments are all reasonable DIY tasks. Beyond that — pump issues, control board faults, door latch failures, water inlet valve problems, and anything involving error codes — these require proper diagnostic tools and disassembly experience. Attempting pump or electrical repairs without the correct knowledge can cause additional damage or void any remaining warranty. If your machine is displaying error codes, producing unusual sounds, or not responding to cycle selections, those are reliable indicators that professional appliance repair in Nepean or elsewhere in Ottawa is the appropriate next step.