SE
Marquis Spas
General Sensor Error
Display shows SE or SENSOR and spa may shut down heating.
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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
Loose or corroded sensor connectors, Failed temperature or high-limit sensor, Mismatched sensor pair, Damaged sensor wiring harness
How to Fix / Troubleshooting
Safety first: Turn off power at the GFCI breaker.
- Inspect sensor connections: Open the control pack and locate the sensor plugs (usually two identical connectors for M7 sensors). Ensure they are fully seated and free of corrosion or moisture.
- Check cables: Follow the sensor cables to the heater tube and look for cuts, abrasions, or rodent damage.
- Test resistance: With sensors unplugged and power OFF, measure resistance across each sensor. They should be similar and within expected range for water temperature. Replace any sensor that reads open, shorted, or far off from the other.
- Replace as a pair if needed: Marquis/ Balboa M7 systems work best with matched sensor pairs. If one fails, consider replacing both.
If SE persists after sensor replacement, the control board sensor circuit may be defective.
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Repair Difficulty
Medium
3/5
Required Part
M7 Sensor Pair for Marquis/ Balboa Heater
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