How to Fix 3 Flashing Dots (: : :) on Your Sundance® Spa

Few things interrupt a relaxing evening faster than stepping outside, lifting your hot tub cover, and seeing three flashing dots (: : :) on your Sundance® Spa topside control panel while the water feels chilly.

The 3 flashing dots icon (sometimes accompanied by an FLO message or alternating temperature display) is one of the most common diagnostic warnings on Sundance® models. It signifies a water flow or high-limit thermal circuit issue. When the spa's circuit board detects that water isn't moving across the heater manifold at the required speed, it automatically shuts off the heater element to prevent dry-firing or thermal damage.

This step-by-step guide walks you through why the 3 flashing dots appear, how to troubleshoot the issue at home, and when to call a professional technician.

What Causes the 3 Flashing Dots Warning?

Your Sundance® Spa relies on a magnetic flow switch inside the heater plumbing loop. When the circulation pump or primary jet pump pushes water through the heater tube, water pressure forces a small magnetic paddle inside the switch to close, signalling to the circuit board that it is safe to energize the heater.

If water flow slows down or stops, the paddle drops open, breaking the circuit and triggering the 3 flashing dots warning.

The most common causes include:

1. Dirty or Dirty/Clogged Filters: Restricted water intake starving the circulation pump.
2. Airlock in the Plumbing: Air pockets trapped in the pump manifold after a drain-and-refill.
3. Low Water Level: Air entering the skimmer assembly instead of water.
4. Failing Circulation Pump: The pump isn't running or spinning fast enough to close the flow switch.
5. Defective Flow Switch or Sensor: Debris stuck in the switch, or a faulty sensor/hi-limit switch.

Step-by-Step Troubleshooting Guide

Verify Water Level:

Quick Check.

Check that your water level is at least halfway up the skimmer weir door or filter intake screen. If the water level is too low, the pump will pull in air, creating pressure drops that open the flow switch. Top off the spa with fresh tap water if needed.

Clean or Bypass Your Filters:

A dirty filter cartridge is responsible for nearly 80% of flow errors.

1. Turn OFF the main GFCI breaker.
2. Remove your MicroClean® filter cartridge(s).
3. Turn the GFCI breaker back ON with the filters removed.
4. If the 3 flashing dots disappear and heating resumes, your filters simply need a deep chemical soak or replacement.

Check for an Airlock:

If the error appeared right after refilling your spa:

1. Turn OFF power at the breaker.
2. Remove the filter cartridges and insert a garden hose directly into the primary standpipe inside the filter bucket.
3. Run water for 1–2 minutes to force trapped air bubbles out through the pumps and heater manifold.
4. Turn power back ON.

Inspect the Flow Switch Paddle:

With power turned OFF at the GFCI breaker, remove the front cabinet access door. Locate the clear micro-flow switch along the heater plumbing loop. Check if foreign debris or hair is jammed inside the clear housing, preventing the magnetic paddle from moving freely.

Difference Between Solid vs. Flashing Dots

• 3 Flashing Dots (: : : flashing): Indicates a temporary flow restriction or open flow switch while a heating cycle is requested. The spa will usually attempt to run pumps to re-establish flow.
• 3 Solid Dots (. . . solid): Indicates a watchdog / high-limit safety trip. The circuit board detected temperatures above safe operating limits or a sensor circuit error. Turn OFF power immediately and allow the heater tube to cool before restarting.

Prevent Flow Issues with Proper Maintenance & Chemistry

Keeping your filtration system clean and preventing scale accumulation inside the heater tube will prevent flow switch errors from occurring.

• Prevent Scale Buildup: Hard water minerals can coat the flow switch paddle and heater element. Using the Mineraluxe System, including the Mineraluxe 2-Part Kit, Mineraluxe Cubes, and Mineraluxe Oxygen, keeps plumbing lines free of scale and biofilm.
• Chemical Balancing: Explore our full range of Hot Tub Chemicals to keep pH and calcium hardness within optimal ranges.

When to Call for Professional Service

If you have cleaned your filters, confirmed proper water levels, and purged airlocks, but the 3 flashing dots persist, you may have a failed circulation pump, bad flow switch, or faulty circuit board relay.

• Replacement Parts: Find genuine OEM switches, sensors, and pumps in our Hot Tub Parts Collection.
• Book Certified Service: If you live in Uxbridge or the Durham Region, schedule an on-site diagnostic with our factory-trained repair team at Hot Tub Service & Repair.
• Upgrade Your Spa: Thinking of upgrading to a new model with advanced filtration and glass-touchscreen controls? Explore our full lineup across the 980 Series, 880 Series, 780 Series, and 680 Series in our main Sundance Spas Collection.