A Jandy JXi or LXi tells you what's wrong in two places: a FAULT message on the front display, and a small LED on the ignition control inside the cabinet that flashes in a pattern. The newer JXiQ drops the flash codes and names more of its faults on the display instead. Here's what each one means, from Jandy's own manuals, how to reset an ignition lockout, and which faults you can clear yourself by checking the pump and filter.
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A Jandy heater fault code is the message the heater's controller shows when one of its safety checks stops it from firing, such as too little water flow, water that's too hot, or a flame that won't light. It tells you which safety check tripped, not always which part failed.
On a JXi and an LXi, the controller shows a FAULT message on the display, and the ignition control has its own LED that flashes a code. Jandy puts the ignition control behind the heater's front panel, so the flash codes are mostly something a technician reads; the display is where you'll see what happened. On the JXiQ, the ignition control's three LEDs only show status (power and communication), and the display carries a much longer list of named faults.
The JXi and LXi share most of their messages; where the wording differs, both are shown. This is what Jandy's manuals list for each:
| Message | What Jandy says it means | What to check first |
|---|---|---|
| CHECK FLOW (JXi) · NO FLOW (LXi) | The water pressure switch isn't sensing enough pressure at the heater's inlet: the pump isn't running, pump pressure is low, the pressure switch is at fault, or a variable-speed pump is set too low | Is the pump running? Then the filter, baskets, valve positions and pump speed. Jandy also says to check the time clock and current time |
| FAULT-HIGH LIMIT | Water in the heater went over the internal limit, or a limit switch is faulty. The JXi has two: 135°F at the heat exchanger's first pass and 150°F at its outlet | Flow. The JXiQ manual points to anything restricting water to the heat exchanger. Testing the switches is a technician job |
| FAULT-CHECK IGN CONTROL | The heater couldn't establish a flame: air-pressure switch tubing, the fan, restricted air at the intake or vent, a broken igniter, low gas supply or no flame at the burner | That the vent and air intake are clear and the gas is on. The rest needs a technician |
| FAULT-HIGH FLUE TEMPERATURE (JXi) · FAULT-FUSELINK/FIELD (LXi) | A flue temperature limit on the JXi; on the LXi, the roll-out switch or the vent temperature limit | Call a technician; these are safety limits |
| FAULT-SHORTED H2O SENSOR · FAULT-OPEN WATER SENSOR | Faulty wiring or a failed water temperature sensor | A technician; the fix is the wiring or a new sensor |
| FAULT-PUMP | Not a fault. In Maintain Temp mode it means the filter pump is currently off | Nothing. Jandy says no service is required |
The JXiQ uses its own names, such as CHECK H2O FLOW, HIGH LIMIT SWITCH, LOW GAS PRESSURE, FLAME SIGNAL FAIL and IGNITION CONTROL LOCKOUT, but the same idea applies: flow faults first, then gas, air and flame.
The JXi and LXi manuals give the same four codes for the ignition control LED:
| LED | What Jandy says it means |
|---|---|
| On continuously | Ignition control fault. Jandy says to refer it to qualified service personnel |
| Single flash | Air flow fault |
| Double flash | Flame present when there is no call for heat. Refer to qualified service personnel |
| Triple flash | Ignition lockout: three unsuccessful attempts to fire |
Treat the double flash seriously: it means the control is seeing flame when nothing asked for heat. Jandy's instruction if overheating occurs or the gas supply fails to shut off is to turn off the manual gas control valve to the heater and not attempt repairs on the gas controls yourself.
When a JXi can't light, the ignition control shuts off the gas valve, purges and tries twice more. After three failed attempts it shuts down and, on the JXi and LXi, tries again by itself after one hour. To get three fresh attempts sooner, Jandy's reset is to turn the control off, turn it back on and select Pool or Spa. On the JXiQ the lockout holds until you turn the power off at the breaker, turn it back on and select Pool or Spa.
One reset after a heater has sat unused is reasonable. If it locks out again, stop: three failed lights in a row means something is keeping the flame from establishing, and Jandy's list of causes is gas supply, the igniter, the fan and air flow, and blockages at the intake or vent. Its fault table even tells indoor installations to check the vent pipe for bird, insect or rodent activity. Pests are a familiar story with heaters that have sat idle all summer; see why heaters won't fire on the first cold morning.
If you smell gas, don't reset anything. Jandy's instructions are not to light any appliance, not to touch electric switches, and to call your gas supplier from a neighbor's phone, or the fire department if you can't reach them.
Jandy says a JXi needs at least 30 gallons per minute through it, up to 100, and that less than 30 can cause nuisance operation, damage the heater or make it turn off. The LXi's range is 30 to 125. That makes the pump the first suspect for a CHECK FLOW or NO FLOW message, and three things cause most of it:
If the pump is running at a sensible speed, the filter is clean and valves are open, and the message is still there, it's the pressure switch or the plumbing, and that's a call for us.
Jandy recommends a qualified service technician for all service and repairs on these heaters, and warns that tampering with the gas controls is dangerous and voids all warranties. Beyond the pump, filter, valves and time clock, the work is ours: pressure and limit switches, the igniter, temperature sensors, the ignition control, fans and gas pressure. Jandy also says not to use the heater if any part has been under water.
Our heater repairs run from about $200 for a small component to $1,000 or more; a replacement gas heater is roughly $4,500 to $5,000 installed. If you're weighing one against the other, read pool heater repair or replace. Different brand on your pad? See our Pentair MasterTemp codes or Hayward H-Series codes, and for anything else, pool heater repair.
The water pressure switch isn't sensing enough pressure at the heater's inlet, so the heater won't fire. Jandy lists the causes as the pump not running, low pump pressure, a pressure switch fault or a variable-speed pump set too low. Check the pump, filter, baskets, valves, pump speed and time clock first. On an LXi the same fault reads NO FLOW.
Turn the control off, turn it back on and select Pool or Spa; that gives it three new attempts to light. Left alone, a JXi tries again by itself after an hour. On the newer JXiQ, Jandy's reset is to turn the power off at the breaker and back on, then select Pool or Spa. If it locks out again, stop resetting and have it checked.
On the JXi and LXi, the ignition control LED gives four codes: on steadily is an ignition control fault, one flash is an air flow fault, two flashes means flame is present with no call for heat, and three flashes is an ignition lockout after three failed attempts. The JXiQ's LEDs only show power and communication status.
Water in the heater went over its internal temperature limit, or one of the limit switches has failed. The JXi has switches at 135°F and 150°F that close the gas valve. The usual cause is not enough water moving through the heat exchanger, so check flow first; testing or replacing the switches is a technician job.
It isn't a fault. Jandy says it's a status message showing that the filter pump is currently off while the heater is programmed in Maintain Temp mode, and no service is required.
Tell us the model and the message on the display. If it's flow, we'll tell you what to check; if it's the switches, sensors, igniter or gas side, we'll come out and fix it. Licensed, insured, serving Cypress and Greater Houston.