A Hayward ProLogic or AquaLogic runs the whole pad: pumps, lights, valves, heaters and, on most systems, the salt chlorinator (Hayward ProLogic guide, p. 4). When it finds something wrong, the Check System LED lights and a message joins the rotating display. Hayward's troubleshooting guide covers the seven problems it sees most often, and the AquaLogic operation manual lists every condition that turns the light on. This guide goes through both: what each message means, what you can check from the keypad, and where it moves behind the panel's dead front.

The ProLogic and the older AquaLogic share one troubleshooting guide; the main board and display part numbers differ between them (Hayward ProLogic guide, p. 17).

Safety first

Everything here is done from the keypad and the breaker. Hayward's guide opens with a high-voltage electrocution warning: only qualified technicians should remove the dead front, the inner cover that keeps the wiring out of reach (Hayward ProLogic guide, p. 2). Nearly every fix past the first step in Hayward's guide involves testing voltages behind it. If a breaker trips again as soon as you reset it, leave it off.

First, find out what the light is about

The light doesn't say why it's on. Hayward's instruction is to go to the Diagnostic Menu and scroll through the items until you find the cause (AquaLogic manual, p. 39). Press Menu until the display shows "Diagnostic Menu", then use the < and > buttons to step through it. The messages also appear in the rotating default display.

The conditions that light Check System, from the AquaLogic manual (pp. 38-39):

Message	What it means
Inspect Cell	Time to inspect the salt cell, about every three months; press + during the message to reset the reminder
Low Salt / Very Low Salt	Salt too low; less chlorine, and the cell's life suffers
High Salt/Amps	The chlorinator has stopped to protect the electronics
Water Sensor, Air Sensor, Solar Sensor	That temperature sensor reads open or short circuit
Chlorinator Cell sensor	The cell's sensor reads open or short circuit
Low Volts	The chlorinator cell voltage is too low
No Cell Power	No cell power detected on the circuit board
Cell Power Error	A cell power error detected on the circuit board
Cell Missing	The chlorinator is enabled but no cell is detected
Chk Flow Switch	The flow switch input is invalid
No Flow-Filter Pump	The filter pump is on but the flow switch has seen no flow for 15 minutes or more
PS-16 Communication Error	On a PS-16, the expansion unit isn't responding

The salt cell messages, Inspect Cell and Low Salt, are covered in salt cell not producing chlorine and low salt reading when the water tests fine. The rest of this guide is about the controller.

No Cell Power, Low Volts and Cell Power Error

Hayward says No Cell Power and Low Volts mean the chlorinator cycle was interrupted because no voltage, or too little, was detected when the cell power relay switched on (Hayward ProLogic guide, p. 19). The chlorinator circuit runs from the ProLogic's own transformer and rectifiers, protected by a 20-amp fuse (p. 5).

Hayward's checks, in order, are the transformer output, the transformer input, the 120 volts reaching the board, and then the 20-amp fuse and the rectifier wiring. Depending on where the voltage goes missing, the fix is the incoming power, the fuse, the transformer or the main board (pp. 18-20). All of those checks are behind the dead front. Cell Power Error is shorter: Hayward says to replace the main board (p. 19).

What you can check: that the panel's breaker is on, and that the chlorinator's other conditions are met (see "The chlorinator shows 0.00 amps" below).

A blank display, or no lights

Hayward says a blank display with no lights can be caused by an abrupt power outage, and that resetting the unit may correct it (Hayward ProLogic guide, p. 22). Turn the panel's breaker off, wait, and turn it back on.

If it stays blank, Hayward's chart works through the display cable, the terminal blocks and the equipment plugged into them, the display fuse (a permanent 2-amp fuse on ProLogic boards, a violet 3-amp fuse on AquaLogic boards), the incoming 120 volts, and finally the display or the main board (pp. 21-24). A piece of connected equipment can take the display down: Hayward's fix for that is to unplug the terminal blocks and add the equipment back one at a time until the problem returns (p. 22). That's technician work.

For blank displays after a storm, see also pool pump not working after a power outage.

Comm Error 1 and Comm Error 2

Comm Error 1 typically happens after a brownout or power outage. Hayward says to turn the breaker that feeds the ProLogic off for 2 minutes, then turn it back on (Hayward ProLogic guide, p. 33). That's yours to try.
Comm Error 2 typically means power is being applied incorrectly to the communication circuit, a problem with the local display, or, rarely, the main board (p. 34).

If a Comm Error survives the 2-minute power cycle, Hayward's next steps are to disconnect the terminal blocks and communication equipment, test the display wiring harness, and replace the display or the main board (pp. 32-34). Hayward also notes that from ProLogic revision 4.10, heaters have their own terminal block, and a heater wired to the wrong position can cause display problems and communication errors (p. 33). If the error started after work on a heater, say so when you call.

CSM Comm Error

CSM is the Chemistry Sensing Module, part of Hayward's Sense & Dispense. Hayward says this error appears when Sense & Dispense is enabled but the module isn't found (Hayward ProLogic guide, p. 26).

The first question is whether you have one. If no sensing module (HL-CHEM) is installed, Hayward's fix is to turn the feature off: press Menu until "Configuration Menu" appears, press and hold < and > together until it unlocks, press > until "Chemistry Wizard" appears, press + to enter, then + again to disable (p. 26). If a module is installed, Hayward's steps are to check its cable and connector and test the communication port, and it says a damaged cable means replacing the module, not repairing the cable (p. 27).

Changing anything in the Configuration Menu changes how the system is set up. If you're not sure what's installed, leave it for the diagnostic.

Chlorinator Off, High Salt/Amps

Hayward says this means the ProLogic has detected the salt cell drawing more current than the threshold for the cell model it's programmed for (Hayward ProLogic guide, p. 29). Hayward's steps (pp. 28-30):

Test the salt with an independent test, using a calibrated salt meter. Hayward's desired salt level is 3,200 ppm. If the salt is above 3,400 ppm, it has to come down (p. 29).
Reset the chlorinator in the Diagnostic Menu, with the pump running (p. 29).
Read the chlorinator voltage in the same menu. If it's too high, Hayward says the main board needs replacing. The guide gives the limit as 35 volts in its steps and says in a note that the circuit should never exceed 33 volts (p. 30).
Check the programmed cell type matches the cell that's installed (p. 30). This matters after a cell has been replaced.

The only way to lower salt is to partly drain the pool and add fresh water (AquaLogic manual, p. 38). Hayward's guide gives a formula for how much to drain, and recommends lowering the water no more than six inches at a time before refilling, to avoid damage to the pool structure or surface (Hayward ProLogic guide, p. 31). Before draining anything, confirm the reading with a second independent test.

The chlorinator shows 0.00 amps, or isn't running

The AquaLogic manual lists what has to be true for the chlorinator to run: the filter pump running, the flow switch seeing flow, the chlorinator set above 0%, the water at the cell between 50°F and 140°F, and the salt within range. If one isn't met, the chlorinator display in the Diagnostic Menu says why (AquaLogic manual, p. 39).

If it reads 0.00A and nothing else is wrong, Hayward says the chlorinator is working normally and is in the off part of its cycle; press + or - to start a new one (p. 39). After the pump first starts, Hayward's guide notes up to a 60-second filter delay before readings appear (Hayward ProLogic guide, p. 29).

The Diagnostic Menu also shows Instant Salt, calculated from the cell's voltage, current and temperature. Hayward says it can differ from the average salt on the main display because salt was just added and hasn't mixed, because of calcium on the cell, or because the cell is aging (AquaLogic manual, p. 40).

Heater Not Firing

The ProLogic tells a heater to fire by closing a low-voltage contact (Hayward ProLogic guide, p. 36). Hayward's checks (pp. 35-38):

Is the filter pump running? The Filter LED should be lit and the pump actually running. If the pump won't come on from the controller, that's the auxiliary problem below.
Is the Heater LED lit with the pump running?
Is the Check System LED on? Clear any errors first. Hayward gives a water temperature sensor failure as an example of an error that stops heating.
Is something else heating? Solar priority can take precedence over the heater.
Raise the heater set points to 104°F to see if it fires. If it still doesn't, Hayward says to call technical support, and to set the set points back first.

Hayward's guide also tests in Service mode, which cancels all scheduled automation and suspends safety features including freeze protection (p. 37). If the heater fires only in Service mode, Hayward says to check that freeze protection isn't active and that solar priority isn't overriding normal heating (p. 37). On the AquaLogic, pressing Service twice gives a timed service mode that returns to normal after 3 hours (AquaLogic manual, p. 5).

If the ProLogic is calling for heat and the heater still won't fire, the heater itself may be showing an error, not be in bypass, or have failed (Hayward ProLogic guide, p. 35). See Hayward pool heater error codes or why your pool heater isn't heating.

An auxiliary that won't run (lights, pump, cleaner)

Hayward says the ProLogic only tries to switch a relay if that auxiliary's LED is lit on the display (Hayward ProLogic guide, p. 40). So:

Press the button for that equipment. If its LED comes on and the equipment still doesn't run, the relay or the wiring is next, which is technician work (pp. 41-43).
If the LED won't come on, something in the automation may be blocking it. On the AquaLogic, Hayward says a relay that won't turn on is probably the interlock feature, which can require the filter pump to be running and the valves to be in the pool-only position, to protect pumps and other equipment (AquaLogic manual, p. 4). Hayward's guide uses Service mode to confirm it: if the LED lights in Service mode, a control feature such as an interlock is overriding it, and when you then try the button normally the system should explain any interlock (Hayward ProLogic guide, pp. 40-41). If the LED won't light even in Service mode, Hayward's next step is replacing the local display (p. 40).

Two more things that look like failures: manual turn-off is disabled while freeze protection is active and the air is below its set temperature (AquaLogic manual, p. 4), and the red System Off button on a remote keypad turns every output off until it's pressed again, which Hayward warns also overrides freeze protection (p. 5).

Temperature sensor and flow messages

Water, Air or Solar Sensor, open or short circuit. The Diagnostic Menu shows each sensor's reading. If a reading is wrong, Hayward says to check where the sensor is placed, and if it isn't placement, the sensor most likely needs replacing. If it reads "Open Circuit" or "Short Circuit", the wiring and its terminal block connection need checking (AquaLogic manual, p. 40), which is inside the panel. The air sensor matters: freeze protection depends on it (p. 38).
No Flow-Filter Pump. The filter pump has been on for 15 minutes or more with the flow switch seeing no flow (AquaLogic manual, p. 39). Check the pump is actually moving water: its basket, the skimmer basket, the filter pressure and the valves. See pump running but no water flow. The Diagnostic Menu shows the flow switch status, with a short delay going from flow to no flow and a longer one the other way (p. 40).
Chk Flow Switch means the flow switch input itself is invalid (p. 39), which is a switch or wiring fault.

When to call

Call when No Cell Power, Low Volts or Cell Power Error appears with the panel powered, when the display stays blank or a Comm Error survives a 2-minute power cycle, when High Salt/Amps returns with the salt tested correct and the cell type right, when the heater or an auxiliary won't run with its LED lit, or for any sensor or flow switch message. We read the Diagnostic Menu, test the transformer, fuses, relays and sensors against Hayward's guide, and tell you what has failed and what putting it right involves before anything is quoted.

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 pool automation repair or salt system repair, or answer a few questions in the Pool Problem Finder. A photo of the display and the label inside the panel door helps. For Jandy and Pentair systems, see pool automation not working.

Sources

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

Hayward, ProLogic/AquaLogic Troubleshooting Guide, Residential, TSG-PL447c (2016).
Goldline Controls (Hayward), Aqua Logic Automation and Chlorination Operation Manual, 092043H (2008), for the PS-4, PS-8 and PS-16.

Hayward, ProLogic, AquaLogic, Goldline and Sense & Dispense are trademarks of Hayward Industries. They are named here only to identify equipment.

Hayward ProLogic and AquaLogic: what the Check System messages mean