When the chlorine drops in a salt pool, it's tempting to blame the cell and start pricing a new one. Usually that's premature. A salt system turns its cell off, or turns it down, for half a dozen reasons that have nothing to do with the cell wearing out, and the lights on the control center tell you which.

This guide covers what Hayward's AquaRite, Pentair's IntelliChlor and Jandy's AquaPure manuals say. If your system's light says Check Salt or low salt but your test kit says the salt is fine, that's a different problem with its own guide: why a salt system says low salt when the water tests fine.

Safety first

Turn the pump and the salt system off at the breaker before you take the cell out. Hayward warns that only qualified technicians should remove the control panel, because of the voltage inside it (Hayward AquaRite guide, p. 2). If you clean a cell yourself, you're handling acid: Hayward and Pentair both say to wear gloves and eye protection, work in a well-ventilated area, and always add acid to water, never water to acid (Hayward AquaRite guide, p. 14; Pentair IntelliChlor guide, p. 20).

No Flow: the cell is off because the water isn't reaching it

Every salt system has a flow switch or sensor, and it won't make chlorine without flow. Pentair says plainly that if the cell doesn't receive adequate flow, no chlorine is produced (Pentair IntelliChlor guide, p. 2). Jandy's display shows NO FLOW and turns the cell off (Jandy AquaPure manual, p. 32).

AquaRite: the No Flow light flashes for 10 to 60 seconds when the pump starts while the system confirms flow. That's normal. If it stays on, the flow switch isn't reporting consistent flow (Hayward AquaRite guide, p. 27).
IntelliChlor: the Flow light is red when there isn't enough flow (Pentair IntelliChlor guide, p. 7).
AquaPure: NO FLOW stays on continuously (Jandy AquaPure manual, p. 41).

What the manuals say to check, in this order, is mostly the pool's circulation, not the salt system: whether the pump is running and has its prime, whether the valves are set so water reaches the cell, whether the strainer baskets are clogged, whether the filter is dirty, and whether something is lodged in the cell (Hayward AquaRite guide, pp. 27 and 29; Pentair IntelliChlor guide, p. 29; Jandy AquaPure manual, p. 41). If the pump itself isn't moving water, start with pump running but no water flow.

Variable-speed pumps and No Flow

This one catches a lot of people after a pump upgrade. Hayward's flow switch needs at least 11 gallons a minute to engage, and Hayward says that if a variable-speed pump is running and No Flow appears, try a higher speed (Hayward AquaRite guide, p. 27). A pump set to its slowest, quietest speed can be moving too little water for the salt cell to switch on, and the pool looks fine until the chlorine runs out. If your pump shows its own fault codes, see the Pentair IntelliFlo and Hayward TriStar VS guides.

When the flow is fine and the light stays on

Then it's the switch, its wiring, or the board. Hayward's checks are that the arrow on the flow switch points the way the water flows, that the switch has about 12 inches of straight pipe before it (the cell counts), and that its connector and wire aren't damaged. Hayward calls the flow switch a safety switch and says not to try to repair the switch or its wire, but to replace it. If a known-good switch doesn't clear the light, the next step is the main circuit board (Hayward AquaRite guide, pp. 27–30). On a Jandy, service code 172 means a flow sensor problem or an unplugged sensor, and Jandy says to contact a pool professional (Jandy AquaPure manual, p. 43). This is testing work, not guesswork.

Inspect Cell, or the cell light flashing

AquaRite: Inspect Cell flashing on its own is a reminder, not a fault. It comes on every 500 operating hours to prompt you to inspect and, if needed, clean the cell. After checking, hold the diagnostic button for about five seconds to reset the timer (Hayward AquaRite guide, p. 15).
IntelliChlor: the Cell light flashing green means the cell needs inspecting, the blades may have calcium buildup, and it is not producing chlorine (Pentair IntelliChlor guide, p. 7).
AquaPure: service code 125 means the cell needs cleaning (every AquaPure code is in our Jandy AquaPure code guide). Codes 120 and 121 (low current to the cell) and 123 (extremely low current) also start with cleaning the cell and checking the DC cord (Jandy AquaPure manual, p. 43).

In each case the first step is the same: take the cell out and look through it. Scale is a white, crusty deposit between the plates. Hayward adds that a cell can look clean and still need cleaning if the salt reading is off or chlorine output has dropped (Hayward AquaRite guide, p. 13).

Hard water makes this a regular job here

East Valley water is hard, and summer evaporation concentrates it. The manuals all point the same way:

Hayward says calcium and pH have the biggest effect on how often a cell needs cleaning (Hayward AquaRite guide, p. 13).
Pentair recommends inspecting the cell every two months if it tends to scale, more often in hard-water areas (Pentair IntelliChlor guide, pp. 19–20).
Jandy warns never to use dry acid to adjust pH in arid areas with heavy evaporation and little fresh water added, because its by-products build up and can damage the cell (Jandy AquaPure manual, p. 37).

Don't overdo the acid. Pentair says not to leave acid in the cell for more than 30 minutes, and that excessive acid washing damages the blades (Pentair IntelliChlor guide, p. 20). If a cell needs acid washing every few weeks, the water balance is the problem to fix, and Pentair suggests having the water tested for calcium hardness and balance.

Cold water: the cell switches itself off

This is the winter one, and it's common from November on. Salt systems protect the cell by cutting back or stopping in cold water:

AquaRite: output scales back to 20% or less at 60°F, and chlorine production stops altogether at 50°F. The display may read COLD (Hayward AquaRite guide, pp. 12 and 38).
IntelliChlor: below 52°F (±3°F), the Cold Water light turns red and the system goes to standby, with no chlorine produced (Pentair IntelliChlor guide, pp. 2 and 7).

Less chlorine is needed in cold water, but not none: Pentair says very little production is needed in cold water as long as free chlorine is kept at 2 to 4 ppm (Pentair IntelliChlor guide, p. 20). Keep testing through the winter, and top it up from another source if the system is resting. If the display says COLD or HOT when the water clearly isn't, Hayward says to clean the cell first, then check that the cell isn't directly downstream of a running heater, and if neither explains it, the cell, which carries the temperature sensor, may need replacing (Hayward AquaRite guide, p. 38).

The light is fine, but the chlorine is still low

If nothing is lit and the chlorine still won't hold, the manuals' troubleshooting tables list the same everyday causes before they get anywhere near the cell (Pentair IntelliChlor guide, p. 28; Jandy AquaPure manual, p. 40):

Low stabilizer (cyanuric acid), in an outdoor pool. Both manuals list it first.
Not enough pump hours. The cell only works while the pump runs. Cut the run time and you cut the chlorine.
Output set too low, or the weather has warmed up without anyone turning the output up.
A heavy load: rain, leaves, a party, pets in the pool. Boost or super-chlorinate, then recheck.
High nitrates or phosphates, or metals in the water. These need a water test.

Hayward also notes that a cell's own salt reading drifts as the cell ages. If the cell is clean and an independent test shows the salt is right, that's normal aging: don't add salt, and raise the output setting instead (Hayward AquaRite guide, p. 43).

When the cell itself is worn out

Cells don't last forever. Pentair says the IntelliChlor cell is designed to run about 10,000 hours, or roughly five years of average use, and has a usage-hours meter you can check from the control panel (Pentair IntelliChlor guide, p. 19). An old cell, clean, with good salt, good flow and good chemistry, that still can't keep up at a high output setting is near the end.

The difference between a worn cell, a scaled cell, a failed flow switch and a failing board is the difference between a cleaning, a small part and a large one. It's worth measuring before buying. See salt system repair.

When to call

Call when No Flow stays on with the pump running well, when a code points at the board, the sensor or the power supply (Jandy's 124, 126, 127 and 170 to 173, for example), when a clean cell still won't produce, or when you'd rather not handle acid. We test the water independently, check the flow switch, read the code against the manual for your system, and test the cell before anyone suggests replacing it.

If you don't know what's wrong, a diagnostic is $120, and it's credited toward your repair if you go ahead. Start from salt system repair, or answer a few questions in the Pool Problem Finder. A photo of the control panel and of the cell's label helps.

Sources

Every manufacturer statement above links to this list. Page numbers are the printed page numbers in each document.

Hayward Industries, AquaRite Troubleshooting Guide Residential, TSG-AQR159d (2017).
Pentair, IntelliChlor Salt Chlorine Generator Model IC15, IC20, IC40, IC60 Installation and User's Guide, P/N 520589 Rev. R (8/7/23).
Zodiac Pool Systems, Jandy AquaPure Electronic Salt Water Chlorinator Installation and Operation Manual, H0325600 Rev F.

Hayward, AquaRite and TurboCell are trademarks of Hayward Industries. Pentair and IntelliChlor are trademarks of Pentair. Jandy and AquaPure are trademarks of Zodiac Pool Systems. They are named here only to identify equipment.

Salt cell not producing chlorine: Inspect Cell, No Flow and the other lights