Balboa · VS / GS series (M7 heater)Fix soon

SnS on a Balboa hot tub: sensors out of balance

The two heater sensors disagree with each other. If SnS alternates with the temperature it may be temporary. If it flashes by itself the spa has shut down.

Also shown as: Sn S, sensor balance, sensors out of sync

Most likely causes

  1. 1Poor water flow through the heatermost likely
  2. 2One sensor drifting or failingcommon
  3. 3Scale buildup on the sensors or in the heaterless common
  4. 4Circuit board faultless common

What to try, in order

  1. Check the water level and clean the filter with the power off at the breaker.
  2. Open all jets and let the pump run for a few minutes to even out the water temperature.
  3. Reset power at the breaker for 30 seconds.
  4. Test calcium hardness and pH. Hard, high-pH water leaves scale on the heater.
  5. If SnS flashes alone and will not clear, book service for sensor testing.

SnS questions

Is SnS serious?

It can be temporary. If it keeps alternating with the temperature for more than a day, or flashes alone, a sensor is probably failing and should be replaced.

Can a dirty filter cause SnS?

Yes. Slow flow lets one end of the heater get warmer than the other, so the two sensors read differently.

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.