FLO and FLC describe opposite flow-switch states. FLO means the switch reads no flow while pump 1 is running. FLC means the switch reads flow while pump 1 is off. In both cases the controller prevents the heater from running. If the problem started after a schedule change or the filter icon is confusing, check the series-specific filtration and purge guide.
| Display | Official meaning | First owner-safe checks |
|---|---|---|
| FLO / ER 00 | No flow detected while pump 1 is running | Water level, blocked intake, filter restriction, closed valves, air lock, and actual pump movement |
| FLC / ER 01 | Flow detected while pump 1 is off | One power reset; service the flow switch or related wiring if it returns |
What FLO means
During a heating call, pump 1 must move water through the heater. If the flow switch remains open, the controller displays FLO and disables the heater. That protection prevents the heater from operating without confirmed water movement.
What FLC means
FLC appears when the flow switch remains closed even though pump 1 is off. That is not a dirty-filter diagnosis. It points to a switch that is stuck, misadjusted, shorted, or otherwise reporting the wrong state.
FLO checks in the correct order
- Turn off power before reaching into the filter or equipment area.
- Confirm the water level is high enough for normal skimmer operation.
- Confirm intake and skimmer openings are clear.
- With stock Progressive Pro Filters, the official path is complete-cartridge replacement. An unofficial teardown can open and rinse the stack, but it is labor-intensive, permanently modifies the cartridge, and cannot restore the media to new condition.
- With reusable pleated filters, remove and rinse them, inspect for damage, and replace them if normal flow does not return.
- Confirm service valves are open.
- After a refill or service, follow the year-specific manual for clearing an air lock.
- Restore power and confirm pump 1 starts and moves water.
If pump 1 does not run, the code returns with filters removed for a brief diagnostic test, or circulation remains weak, stop. Pump, wiring, controller, valve, plumbing, or switch diagnosis belongs to a qualified technician.
FLC checks
Cycle power once. If FLC returns while pump 1 is off, do not keep resetting the spa and do not buy filters as a guess. The flow-switch circuit requires inspection. The heater stays disabled because a false flow signal would make heater operation unsafe.
Where Kit v3 helps—and where it does not
Kit v3 helps a compatible 2020+ Custom Series owner move away from sealed proprietary cartridges to reusable generic filters that can be removed, rinsed, cleaned, and reused. This can make routine filter maintenance simpler and lets the owner replace a loaded cartridge without dismantling sealed media.
Kit v3 does not repair a failed pump, stuck flow switch, closed valve, air lock, damaged sensor, heater, controller, or wiring. If a mechanical or electrical fault causes the code, an adapter cannot fix it.
Filter Not Present is a different message
With Kit v3, Filter Not Present remains expected because the adapter does not emulate the stock detection signal. FLO and FLC are actual flow-switch faults. Do not treat the expected detection message as proof of a hydraulic failure.
When to call service
- FLC returns after one reset.
- FLO returns with correct water level and an unrestricted filter path.
- Pump 1 does not start or sounds abnormal.
- The spa trips a breaker, leaks, overheats, or displays a heater/probe code.
- You would need to open the control pack or work on energized equipment.
Order Kit v3 for a compatible filter setup
If the recurring problem is the sealed proprietary-filter path—not a failed component—check the confirmed 2020+ Custom Series compatibility list, then order Kit v3. Compatible reusable filters are required and sold separately.
FAQs
Can a restricted filter cause FLO?
Yes. A restricted filter can reduce flow enough to keep the switch open while pump 1 runs. It is one possible cause, not the only cause.
Can a dirty filter cause FLC?
No direct manufacturer source identifies dirty media as the reason a switch reads flow while the pump is off. A returning FLC needs flow-switch circuit service.
Should I keep resetting the spa?
No. One reset is enough to rule out a transient display state. A returning code requires diagnosis.
Will Kit v3 clear every flow code?
No. It changes the filter path only. It does not repair hydraulic, electrical, heater, sensor, or control faults.
References
This is an independent aftermarket owner resource. Spa Filter Adapter is not affiliated with, endorsed by, or approved by Arctic Spas. Product and maintenance claims are separated by system and tied to the sources below.