Top 10 Heating Coil Problems in Commercial Dishwashers & How to Fix Them

Commercial dishwashers are essential for keeping kitchens running efficiently, but heating coil problems can quickly disrupt operations. These coils are responsible for maintaining the high temperatures needed to sanitize dishes, so any malfunction can lead to longer wash times, incomplete cleaning, or even equipment damage. Understanding the common issues that affect heating coils is crucial for restaurant owners, kitchen managers, and maintenance teams.
In this guide, we’ll explore the top 10 commercial dishwasher heating coil problems and provide practical solutions to fix them. From electrical failures to mineral buildup, you’ll learn how to troubleshoot and resolve each issue effectively, ensuring your dishwasher operates reliably and your kitchen stays on schedule.

Why Commercial Dishwasher Heating Coils Fail

Commercial dishwasher heating coils are crucial for high-temperature cleaning, but they can fail due to several common issues. Understanding these causes and maintaining proper commercial dishwasher parts can help prevent downtime.

• Limescale and Mineral Buildup: Hard water deposits reduce efficiency and cause overheating.

• Electrical Overload: Surges or improper wiring can burn out coils.

• Corrosion: Continuous exposure to water and chemicals erodes the metal.

• Frequent Cycling: Constant on/off operation shortens coil lifespan.

• Poor Maintenance: Neglecting cleaning and inspections accelerates wear.

• Improper Installation: Incorrect coil placement can lead to uneven heating.

• Chemical Damage: Strong detergents or sanitizers can weaken coil material.

Regular inspection and proper care significantly extend the life of heating coils and help prevent dishwasher temperature issues.

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Top 10 Heating Coil Problems in Commercial Dishwashers

A commercial dishwasher not heating properly can disrupt kitchen operations. Early heating coil failure signs include uneven water temperature, longer wash cycles, and visible corrosion, helping prevent costly downtime.

1. High CO₂‑Driven Corrosion
In areas with high dissolved CO₂, the copper sheath of the coil corrodes prematurely, causing electrical shorts or water leakage.
Causes: Elevated carbon dioxide concentration in water that attacks the copper sheath.
Symptoms: Blue-green staining on coil, erratic heating, and short circuits.
Fixes:

• Test water chemistry and reduce CO₂ levels.

• Replace coil with a corrosion-resistant or coated element.

• Monitor the coil regularly to detect early signs of chemical damage.

2. Burnt‑out Coil
The heating coil can burn out completely due to prolonged use or electrical overload, causing the dishwasher to stop producing heat entirely.
Causes: Electrical overload, aging coil, frequent high-temperature cycles.
Symptoms: Water remains cold, cleaning is incomplete, dishwasher fails to heat.
Fixes:

• Test coil continuity with a multimeter.

• Replace the heating element if an open circuit is detected.

• Inspect wiring and connections to prevent recurrence.

• Schedule periodic coil inspections to catch early overheating.

3. Limescale / Mineral Buildup
Hard water and mineral deposits accumulate on the coil, reducing heating efficiency and causing uneven water temperature.
Causes: Hard water, lack of descaling, high mineral content.
Symptoms: Longer wash cycles, partially cleaned dishes, uneven heating. Fixes:

• Descalcify the coil regularly.

• Install a water softener or filtration system.

• Clean the dishwasher interior frequently.

• Track water hardness to adjust maintenance frequency.

4. Thermostat or High‑Limit Switch Fault
A faulty dishwasher high-limit thermostat stops the coil from reaching the proper temperature.
Causes: Worn sensors, electrical faults, and temperature control failure.
Symptoms: Water never reaches the required heat, and cycles cut off unexpectedly.
Fixes:

• Test the thermostat and high-limit switch for continuity.

• Replace faulty sensors or switches.

• Inspect wiring leading to thermostat for damage.

• Record temperature readings during cycles to ensure proper heating.

5. Manufacturing Defects / Impurities
Internal defects in the coil’s resistance wire or sheath from poor manufacturing can lead to early failure.
Causes: Impurities in resistive wire, uneven magnesium-oxide packing, poor welds.
Symptoms: Early burnout, intermittent shorts, failure soon after installation.
Fixes:

• Replace the element under warranty if detected early.

• Source high-quality spare parts from OEM suppliers.

• Inspect new coils for visible defects before installation.

6. Localized Overheating due to Poor Heat Transfer
Certain segments of the coil overheat because of poor thermal coupling, eventually causing wire breakage or arcing.
Causes: Scaling/sludge buildup, degraded insulation, sheath damage.
Symptoms: Hot spots, blistered sheath, arcing faults, coil failure.
Fixes:

• Clean the scale and sludge from the coil.

• Inspect and repair the sheath if damaged.

• Replace the faulty coil with a properly rated element.

• Monitor temperature across coil segments during operation.

7. Floating Star‑Point Wiring Misconfiguration
Incorrect or floating neutral wiring in three-phase coils causes slow heating or imbalance, stressing the coil.
Causes: Poor wiring practices, missing neutral connection.
Symptoms: Very slow heat-up, one leg overheating, uneven load.
Fixes:

• Verify wiring against the manufacturer’s diagram.

• Connect neutral or rewire correctly.

• Test balance across phases.

• Label wiring clearly to avoid future misconfigurations.

8. Control Board Relay “Sticking” / Failed Coil Activation
A relay on the control board may fail to switch, preventing the heating coil from energizing.
Causes: Worn or shortened relay contacts on the control board.
Symptoms: No heating, although coil tests fine; error codes; intermittent heat.
Fixes:

• Replace the faulty relay on the control board.

• Check solder joints and connector pins.

• Re-run diagnostics after replacement.

• Keep spare relays on hand for quick replacement.

9. Dry‑Firing (Heating Without Water)
Operating the coil without sufficient water causes overheating and potential failure.
Causes: Low water level, faulty float switch or sensors, or operator error.
Symptoms: Coil glows red-hot, burning smell, dishwasher shuts down.
Fixes:

• Verify water level sensors and float switches.

• Ensure proper water fill before heating starts.

• Train operators to avoid running empty cycles.

• Install alarms or automatic shut-off for low-water conditions.

10. Sheath Degradation due to High-Temperature Corrosion
The coil’s outer sheath corrodes internally from high-temperature chemical attack, compromising insulation.
Causes: Detergent or sanitizer chemical attack, oxidation, and long use at high heat.
Symptoms: Insulation breakdown, short to ground, erratic heating.
Fixes:

• Replace the coil with a chemically resistant material.

• Use compatible detergents and chemicals.

• Perform frequent inspections for early sheath damage.

• Maintain logs of chemical use and cycle temperatures for preventive care.

How to Quickly Diagnose a Commercial Dishwasher Heating Coil Failure

Dishwasher heating element problems are one of the most common causes of poor dishwasher performance. Quick and accurate diagnosis can save downtime and prevent costly replacements.

• Visual Inspection: Look for discoloration, corrosion, blistering, or mechanical damage, including bent coils or loose mounting clips.

• Continuity & Resistance Tests: Use a multimeter to check coil continuity and measure resistance; deviations indicate internal damage or shorted turns.

• Cycle Discrepancy: If the coil heats in diagnostic/test mode but not during normal cycles, check relays, control boards, or sensors.

• Bright Red Glow / Hot Spots: Unusually bright or uneven heating suggests coil overwork or localized failure.

• Mechanical Interference: Ensure spray arms or other components are not touching or damaging the coil.

• Sensor & Control Checks: Faulty optical water-intensity (OWI) sensors or high-limit switches can mask heating issues.

• Flange Corrosion: Inspect coil mounting points for galvanic corrosion, especially in hard-water areas, as it can cause intermittent heating failures.

Technicians can use commercial dishwasher diagnostics to quickly pinpoint coil failures. This helps decide whether repair or replacement is needed.

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Step-by-Step Fixes for Common Heating Coil Problems in Commercial Dishwashers

Quickly addressing problems helps fix commercial dishwasher heating issues, keeping your machine running efficiently and preventing costly downtime.

Step 1: Check for Burnt or Open Coil
Test the coil with a multimeter to determine continuity and replace it if the element is broken.

Step 2: Remove Limescale Build-Up
Descale the coil regularly and consider installing a water softener if your water supply is hard, or use vinegar and citric acid for stubborn mineral deposits.

Step 3: Inspect Thermostat and High-Limit Switch
Check sensors for faults and replace any malfunctioning components to restore proper temperature control.

Step 4: Fix Mechanical Damage or Misalignment
Ensure coil mounting clips are secure, and spray arms or other parts do not touch or bend the coil; re-anchoring loose coils prevents vibration-driven damage.

Step 5: Clear Melted or Sticky Residue
Remove any melted plastic on the coil carefully, and clean sticky residues from new replacement parts using mild solvents or isopropyl alcohol.

Step 6: Reset Error Codes After Replacement
After replacing components, manually clear error codes to ensure the coil heats properly in normal wash cycles.

Step 7: Check Control Board or Relay Issues
Test relays and inspect control wiring, replacing any faulty components to ensure proper coil activation, especially after major part swaps.

Step 8: Verify Performance in Real Cycle
Run a full wash cycle, not just diagnostic mode, to confirm the coil heats consistently and the dishwasher reaches proper temperatures.

When to Replace the Commercial Dishwasher Heating Coil

Knowing when to replace a heating coil prevents downtime and ensures proper dishwasher performance.

• Failed Continuity: Multimeter tests show an open or broken circuit.

• Poor Heating Performance: Water heats unevenly or fails to reach the proper temperature.

• Frequent High-Limit Trips: Safety switches repeatedly trip during operation.

• Severe Limescale: Insulating scale reduces heat transfer, causing burnout.

• Galvanic Flange Corrosion: Corrosion at the flange can cause leaks or shorts.

• Stress-Corrosion or Thermal Cycling Damage: Micro-cracks or hot spots reduce coil integrity.

• Foreign Object Burns: Melted plastic or debris marks indicate compromised coil function.

Timely heating coil replacement prevents downtime and ensures your dishwasher performs efficiently.

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Maintenance Tips to Prevent Heating Coil Problems in Commercial Dishwashers

Regular heating element maintenance keeps your dishwasher efficient, extends its lifespan, and reduces costly repairs.

• Rotate Heavy Use Cycles: Avoid running consecutive high-temperature cycles. Rotating lighter cycles prevents overheating and coil strain.

• Flush with Vinegar Solution: Run a vinegar or food-safe rinse occasionally. This removes hidden mineral buildup that standard descaling may miss.

• Check Water Inlet Pressure: Low or fluctuating water pressure makes the coil work harder. Maintain consistent flow for efficient heating.

• Inspect for Scale Hot Spots: Look for uneven scaling or discoloration. Targeted cleaning prevents localized overheating and coil failure.

• Tighten Mounting and Brackets: Loose brackets allow vibration. Securing them reduces mechanical stress and shorts.

• Use Eco-Friendly Detergent: Avoid corrosive detergents. Use balanced, manufacturer-recommended options to preserve the coil.

Wrapping Up: Heating Coil Troubles and Solutions

Commercial dishwasher heating coils are essential for high-temperature cleaning and smooth kitchen operations. Performing regular heating coil troubleshooting helps catch issues early and maintain efficiency. Timely commercial kitchen dishwasher repair prevents costly downtime and ensures long-lasting performance.

Key Takeaways:

• Install Water Filtration: Using inline filters reduces sediment and particulate buildup that can damage coils.

• Check Voltage Stability: Fluctuating power can weaken coils; use surge protectors or dedicated circuits.

• Inspect Mounting Integrity: Regularly verify that brackets and supports are secure to prevent vibration damage.

• Schedule Seasonal Deep Cleans: Comprehensive seasonal maintenance targets hidden buildup and corrosion.

• Audit Detergent Dosage: Overuse can accelerate chemical wear; ensure correct proportions for efficiency.

• Use Coil-Specific Lubricants: Some coil connections benefit from food-safe anti-corrosion coatings on terminals.

• Track Cycle Duration: Avoid excessively long cycles that overstress the heating element.

By addressing a faulty dishwasher heating coil promptly, commercial kitchens can maintain consistent dishwasher performance. Early detection and following a proper heating element repair guide help safeguard equipment from further damage and reduce downtime. Proactive maintenance steps also improve efficiency and minimize unexpected repair costs.

FAQs

How much does it cost to replace a heating coil in a dishwasher?

The cost to replace a commercial dishwasher heating coil typically ranges from $100 to $400, depending on the model and brand. Labor charges may add extra, so professional installation is often recommended.

Why is my commercial dishwasher not heating up properly?

A dishwasher may fail to heat due to a burnt-out coil, faulty thermostat, or tripped high-limit switch. Electrical issues or mineral buildup on the heating element can also prevent proper heating.

What causes a commercial dishwasher heating element to burn out?

Heating elements can burn out from frequent high-temperature cycles, electrical overloads, or poor water coverage. Corrosion and chemical damage from harsh detergents also shorten coil lifespan.

Can scale buildup affect the heating coil in a commercial dishwasher?

Yes, hard water deposits form limescale on the coil, reducing heat transfer and causing uneven water temperature. Over time, this can lead to coil overheating and eventual failure.