FS1
AquaCal
Water Inlet Temperature Sensor Fault
Display shows FS1; heater will not operate or operates erratically.
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Open or shorted inlet thermistor, Damaged sensor harness, Corroded connector at control board, Incorrect replacement sensor installed
How to Fix / Troubleshooting
Safety first: Disconnect power before working on sensors or wiring.
- Identify FS1 sensor: Refer to the AquaCal wiring diagram to locate the inlet water sensor (FS1). It is usually installed in the inlet side of the water manifold.
- Inspect wiring and connector: Check for cuts, abrasions, or rodent damage along the sensor cable. Reseat the connector on the control board.
- Resistance check (advanced): With the sensor disconnected and using a multimeter, measure resistance and compare to AquaCal's temperature‑resistance chart. Replace if readings are out of range.
- Install correct sensor: Use only AquaCal‑approved replacement sensors; mismatched thermistors can cause persistent FS1 errors.
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Repair Difficulty
Medium
3/5
Required Part
Inlet Water Temperature Sensor
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