Common problems with Hood-type dishwasher and solutions

Commercial conveyor dishwashers are highly efficient dishwashing machines primarily used in high-traffic locations such as large restaurants, hotels, and cafeterias.

Hood-type dishwasher, due to their relatively compact structure and frequent use, are prone to common faults over extended periods of use. The following is a classification of common faults, their possible causes, and corresponding solutions, covering common issues for both commercial and residential models, along with notes on precautions:
1. Core Function Faults: No Water Inflow / Slow Water Inflow  
Fault Symptoms  
After starting the washing program, no water flows into the tank, or the water level rises extremely slowly and cannot reach the normal washing water level.
Some models may trigger a “low water alert” (indicator light flashing or audible alert).
Possible Causes and Solutions  
Water Supply Issues  
Check if the dishwasher's water inlet valve is fully open (typically located under the sink for residential models, or on the wall or back of the unit for commercial models). If the valve is not fully open or partially open, fully open it;
Confirm that the tap water pressure is normal (normal pressure should be 0.15-0.3 MPa): If the water pressure is too low (e.g., during peak usage hours), pause use and restart once the pressure has recovered; if the pressure remains low over the long term, residential models can install a booster pump, while commercial models should contact property management to inspect the water pipes.
Blocked/damaged inlet pipe
After turning off the water supply, remove the inlet hose (residential: connects the dishwasher to the faucet; commercial: connects the equipment to the main inlet pipe), and check the inside of the hose for blockages caused by sand, scale, or debris. Rinse with clean water. If the hose is aged or cracked, replace it with a food-grade pressure-resistant hose of the same specification (commercial models are recommended to use stainless steel braided hoses for greater durability).
Inlet valve malfunction
The inlet valve is the core component controlling water intake. If the valve core is stuck or the coil is burned out, water intake will be impossible.
Residential models: After disconnecting the power, remove the inlet valve housing and gently sand the valve core with fine sandpaper (to remove scale). If this is ineffective, replace the inlet valve with the same model (parts can be purchased through the brand's after-sales service);
Commercial models: Since the water inlet valve has a higher power rating, it is recommended to first use an electrical tester to check if the coil is powered (must be done after powering off to avoid electric shock). If the coil does not respond, directly replace the commercial-grade water inlet valve (self-repair is not recommended to prevent leaks due to poor sealing).
Abnormal water level sensor
If the water level sensor (float-type or pressure-type) is covered with scale or stuck, it may incorrectly detect “water level full,” causing the water supply to stop.
Remove the sensor housing (typically located above the water tank), and use a soft cloth dipped in white vinegar to wipe the float or sensor probe to remove scale. If the float is broken or the sensor wires are loose, replace the sensor or securely reconnect the terminals.

2. Core Function Failure: No Heating / Slow Heating  
Failure Symptoms  
The washing water temperature cannot reach the set value (typically, washing temperature requires 50-60°C, and disinfection temperature requires 80-90°C), dishes are not thoroughly cleaned of grease, or there is still moisture after drying.
In some models, the heating indicator light remains on, but the water temperature does not change.  
Possible Causes and Solutions  
Heating element scaling/burnout  
In dishwashers with removable lids, heating elements are often “submerged-type,” and prolonged use with hard water can lead to scale buildup, reducing heating efficiency; severe scaling can wrap around the heating element, causing overheating and burnout.
Solution: After disconnecting the power, open the water tank lid, remove the heating element (commercial models require removing the mounting screws, while residential models are typically snap-on), soak it in a specialized descaling agent (such as citric acid descaler) for 30 minutes, then clean the scale with a soft-bristle brush; If the heating element surface shows obvious deformation, bulging, or shows “no resistance” when tested with a multimeter after powering on, replace it with a heating element of the same power rating (note: commercial models typically have heating elements rated at 3-6 kW; ensure voltage compatibility to prevent overloading).
Thermostat/temperature sensor malfunction
If the thermostat (manual reset type) trips due to overheating (e.g., scale buildup causing poor heat dissipation from the heating element), it will cut off the heating circuit; if the temperature sensor (NTC thermistor) malfunctions, the mainboard will be unable to detect water temperature and will stop heating.
Thermostat: In commercial models, the thermostat is typically located on the side of the water tank and has a “reset button.” Pressing it should produce a “click” sound to restore functionality; if heating does not resume after resetting, the thermostat must be replaced;
Temperature Sensor: Use a multimeter to measure the sensor's resistance value (approximately 10kΩ at room temperature, with resistance decreasing as temperature increases). If the resistance reads 0 or infinite, the sensor is damaged and should be replaced with the same model.
Poor contact in the heating circuit
Loose or oxidized heating element terminals, or aged and broken wiring, can cause the heating element to fail to receive power.
After disconnecting the power, inspect the heating element terminals, use sandpaper to remove the oxidized layer, and tighten the screws securely. If the wiring is broken, use high-temperature-resistant wire (capable of withstanding temperatures above 150°C) to reconnect the circuit, and wrap it with insulating tape.

3. Cleaning Effectiveness Issues: Dishes Not Cleaned Properly / Residue Remains
Issue Symptoms
Dishes still have grease, food residue (such as rice grains or sauce residue), or white water stains after drying.
Detergent residue remains in the crevices of some dishes (e.g., bowl rims, chopstick holders).  
Possible Causes and Solutions  
Spray arm blocked / not rotating  
The spray arm is a core cleaning component. If food residues (e.g., bone fragments, vegetable leaves) block the spray nozzles or the bearings are jammed, water flow cannot be sprayed evenly, resulting in more cleaning blind spots.
Solution: Remove the upper and lower spray arms (unscrew counterclockwise to remove), rinse the spray holes with clean water, and use a thin metal wire (such as a paperclip) to gently clear stubborn residues (be careful not to puncture the large spray holes to avoid reduced water pressure); check if the spray arm bearings are stuck, and if they rotate poorly, apply a small amount of food-grade lubricant (high-temperature grease is recommended for commercial models).
Clogged filtration system
The bottom of a lift-up dishwasher typically has 1-2 layers of stainless steel filters (coarse filter + fine filter). If not cleaned promptly, food residues can clog the filters, obstructing water circulation and causing dirty water to repeatedly rinse the dishes.
Solution: After each wash cycle, remove the filter (residential models are typically pull-out, while commercial models require unscrewing the mounting screws), rinse off any remaining food particles with clean water, and thoroughly clean the filter once a week using a soft-bristle brush and neutral detergent. If the filter is damaged (with holes), replace it immediately to prevent debris from entering the wash pump and causing damage to the pump housing.
Detergent/water softener issues
Insufficient detergent or incompatible type: Commercial models require specialized “low-foam dishwasher detergent.” Using household dish soap will produce excessive foam, blocking the spray arms. If the detergent dosage is too low, it cannot effectively break down grease.
Solution: Follow the dosage instructions in the manual (commercial models typically have an automatic dispenser; check if the dispenser is clogged to ensure accurate dosage);
Lack of water softener: In hard water areas, failing to add water softener will leave white scale (calcium and magnesium ion residues) after washing;
Solution: For household models, install a water softener at the water inlet; for commercial models, regularly add specialized water softening salt (top up to the marked level in the salt tank).
Insufficient water temperature/pressure
If the water temperature is below 50°C, the detergent's activity is insufficient, making it difficult to break down grease; if the washing pump pressure decreases (e.g., due to debris inside the pump), the water flow's impact force weakens;
Solution: First, troubleshoot the “no heating” issue (refer to Section 2) to ensure the water temperature meets requirements; if water pressure is low, disassemble the washing pump's inlet (requires power disconnection and drainage), clean debris from the pump; if the pump body makes unusual noises or leaks, replace the washing pump.

4. Operational and Safety Faults: Lid Cannot Close / Alarm Triggers After Closing  
Fault Symptoms  
After opening the lid, it cannot be closed smoothly, or the machine does not start after closing, triggering the “Lid Not Closed Properly” alarm.
Some commercial models have heavier lids, which may cause sticking or misalignment during closure.  
Possible Causes and Solutions  
Lid Hinge Failure  
The hinge is the core component connecting the lid to the machine body. Long-term use may cause screw loosening or hinge shaft wear (commercial models experience more wear due to frequent lid opening and closing);
Solution: Use a wrench to tighten the hinge mounting screws (residential models typically use Phillips screws, while commercial models use hex screws); if the hinge shaft is dry, apply a small amount of high-temperature grease; if the hinge is broken or severely deformed, replace it with a hinge of the same specification (note: the lid is heavy, so two people should assist during replacement to prevent it from falling).
Aged sealant strip on the lid
If the sealant strip on the edge of the lid (which prevents water leakage during cleaning) is aged, deformed, or detached, it will cause the lid to fail to seal properly when closed, triggering a “seal detection alarm”;
Solution: Remove the aged seal strip, clean any dirt from the seal strip groove, and replace it with a food-grade seal strip of the same model (for household models, a universal version can be purchased online; for commercial models, contact the brand's after-sales service). Ensure the seal strip is fully seated in the groove without any wrinkles during installation.
Safety latch malfunction
Some models are equipped with a “lid safety lock” (to prevent the lid from accidentally opening during cleaning). If the lock spring is loose or the latch is worn, the lock may fail to secure properly;
Solution: Disassemble the lock housing, check if the spring has fallen out, and reinstall it if necessary. If the latch is worn, lightly sand the contact surface of the latch with sandpaper. If it still fails to secure properly, replace the lock assembly.