Balboa · VS / GS seriesFix soon

SnA on a Balboa hot tub: sensor a fault

The sensor plugged into the Sensor A jack is not giving a valid reading, and the spa has shut down. The water is not dangerous, but the tub will not run until the sensor circuit is fixed.

Also shown as: SA, Sn A, sensor A

Most likely causes

  1. 1Failed temperature sensormost likely
  2. 2Loose or corroded sensor plug at the boardcommon
  3. 3Damaged sensor cable (often from rodents)common
  4. 4Fault on the circuit boardless common

What to try, in order

  1. Turn the tub off at the breaker for 30 seconds, then back on. A one-off glitch may clear.
  2. If the code briefly appears during an overheat, let the tub cool and see if it goes away.
  3. With the power off at the breaker, look in the equipment bay for chewed or pinched sensor wires. Do not open the control box.
  4. If the code stays, the sensor most likely needs replacing. Note the control pack model number from the label for ordering.

SnA questions

Can I use my hot tub with an SnA code?

No. The control shuts the spa down when it cannot trust a sensor, so pumps and heat will not run normally.

Are Sensor A and Sensor B the same part?

On most Balboa M7 systems they are the same type of sensor in two positions on the heater. Check your pack model before ordering.

Related codes

Balboa -- · Temperature not yet knownBalboa CHEK PH · Maintenance reminderBalboa CLN FLTR · Filter reminderBalboa CNFG FAIL · Configuration errorBalboa dr · Heater may be dryBalboa dry · Heater is dryBalboa Ecn · Economy modeBalboa FLO · Low water flow

General guidance. Follow your manufacturer's instructions; anything inside the control box is work for a licensed professional. Updated October 5, 2026.