Manitowoc E20 Error Code — What It Means
The E20 error code is a Water System Fault. It means the control board detected an abnormal water level or an out-of-range measurement from either the high or low water probe. The machine failed to sense water reaching the high-level probe within the required timeframe during the fill and circulation cycle, or the board detected that the high or low water sensors remained active (or inactive) incorrectly at the end of a harvest cycle.
In some scenarios, E20 appears if the system senses water high but never senses water low, or if the evaporator outlet temperature (T4) drops below 10°F too early in the freeze cycle (6 to 7.5 minutes), indicating a lack of water load on the evaporator. This often results from insufficient water flow due to a clogged filter, failed pump, or valve issue.
Before You Replace Anything
Technicians sometimes replace the control board when the real problem is mineral buildup or a corroded connection at the probe terminals. Always clean the probes and check the connections before ordering a board.
Common Causes
- Clogged water filter (~40%) A dirty filter prevents water from reaching the high-level probe, triggering the fault.
- Mineral buildup on probes (~25%) Scaling creates a false conductivity bridge that makes the sensor read wet even when dry.
- Stuck dump valve (~15%) If the dump valve plunger is stuck open, water drains to the floor instead of filling the evaporator.
- Failed water pump or inlet valve (~10%) The pump may not be running, or the inlet valve is stuck closed, preventing water fill.
- Corroded probe connections (~7%) The wiring connection at the control board for the water probes may be corroded, causing signal loss.
- Out-of-range probe resistance (~3%) If a probe is more than 10% out of range compared to the factory chart and clean, it needs replacement.
Quick Diagnosis
Answer these to narrow it down fast.
Is water leaking onto the floor during the freeze cycle?
No: Check the water filter and pump operation next.
Is the water filter visibly clogged or discolored?
No: Inspect the water probes for mineral deposits or corroded wiring.
Do the high or low water probes have visible white or brown mineral buildup?
No: Measure probe resistance against the factory chart and check connections at the control board.
Step-by-Step Fix
- Check and replace the water filter. Inspect the internal filter for clogs or discoloration. If dirty, replace it immediately. This is the most common cause of E20.
- Verify water flow and pump operation. Listen for the inlet valve opening and confirm the pump is running. If no water enters the machine, troubleshoot the valve and pump circuits.
- Inspect the dump valve. Check if the dump valve plunger is stuck open by looking for water leaking to the floor during the freeze cycle. Clean the plunger and seat if dirty.
- Clean the water probes. Descale the high and low water probes using a food-grade descaler to remove mineral bridges. Do not sand the probes, as this accelerates rescaling.
- Measure probe resistance. If cleaning fails, measure the resistance of each probe with an accurate temperature reference and compare to the factory chart. If the probe is more than 10% out of range and clean, replace it.
- Check probe connections. Inspect the wiring connections at the control board for corrosion or looseness. Clean or reseat the terminals if needed.
- Monitor evaporator temperature. If the T4 (evaporator outlet) temperature drops below 10°F within 6 to 7.5 minutes of the freeze cycle start, the machine has no water load. Return to step 1 and verify water flow and probe operation.
Parts Often Needed
| Part | Notes |
|---|---|
| Manitowoc water filter | Amazon | Match the filter part number to your model. Most units use a replaceable cartridge. |
| High or low water level probe | Amazon | Order by model number. Only replace if resistance is more than 10% out of range and cleaning did not help. |
| Dump valve plunger kit | Amazon | Includes plunger and seat. Order if the valve is stuck open or leaking. |
| Water inlet valve | Amazon | Replace if the valve does not open or water does not flow into the machine. |
When to Call a Pro
Call a commercial refrigeration technician if you are not comfortable working on ice machines or if the steps above do not clear the fault. Ice machines operate under food-safety regulations and require proper cleaning and descaling procedures. If the evaporator is damaged or not being cleaned regularly, the technician may recommend replacing the evaporator. A pro will also have the tools to measure probe resistance accurately and compare it to the factory chart, and can diagnose control board or wiring issues that are beyond typical DIY scope.
Rough cost: A pro service call runs about $150-400.