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COOL on a Jacuzzi / Sundance hot tub: water 20°f below set

The water is more than 20°F below the set temperature. The pump and heater turn on to bring it back up. This is normal after a refill.

Also shown as: COL, CL, cold

Most likely causes

  1. 1Fresh refill with cold watermost likely
  2. 2Cover left off for a long timecommon
  3. 3Tub not heating because of another faultless common

What to try, in order

  1. Keep the cover on and let the tub heat.
  2. Check again in a few hours. A 240V tub typically gains 3 to 6°F per hour.
  3. If the temperature is not rising, check for a second code and clean the filter.
  4. If it still will not heat, see our guide on a hot tub that is not heating.

COOL questions

Is COOL an error?

No. It is a status message that the water is well below the set point.

How long until COOL goes away?

After a cold refill, expect several hours on 240V and up to a day or more on a 120V plug-in tub.

Related codes

Jacuzzi / Sundance -- · Watchdog shutdownJacuzzi / Sundance FL1 · No flow detectedJacuzzi / Sundance FL2 · Flow switch stuck closedJacuzzi / Sundance FLO · Flow switch problemJacuzzi / Sundance HOLD · Panel buttons locked outJacuzzi / Sundance ICE · Freeze protection activeJacuzzi / Sundance OH · Overheat protectionJacuzzi / Sundance Sn1 · Hi-limit sensor fault

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