Jandy Pool Heater Error Codes: JXi Check Flow, Check IGN Control, LED Flashes, and LXi Faults — A South Florida Pool Pro's Guide

The most likely fix on a Jandy heater code: check flow before you touch the heater. The message we see most on South Florida JXi heaters is CHECK FLOW, and Jandy's own manual lists four causes for it: a pump that isn't running, low pump pressure, a variable-speed pump set too low, or a faulty pressure switch. Three of those four live outside the heater. The other message worth knowing by name is FAULT-CHECK IGN CONTROL, a failed light-off that belongs with a licensed tech. Wording varies by manual revision, and the older LXi uses slightly different messages, so match your display against your heater's manual.

I've been on Florida pool routes since the late 1990s, and the pattern on Jandy heaters has held the whole time: the heater reports the problem honestly, and the problem usually sits upstream of it. The code meanings below come from Jandy's installation and operation manuals for the JXi, LXi, JE, and VersaTemp. The order we check things in is ours.

How a Jandy heater reports a fault

A JXi or LXi reports a problem two ways. The front display prints a message in words. Inside the cabinet, the ignition control board has an LED that flashes a count. If you searched for a “Jandy heater service light,” the display message is what you read first. The flashing LED is the light Jandy documents for ignition faults, and it sits behind a panel you shouldn't be pulling on a gas appliance.

Jandy JXi and LXi error-code quick reference

CHECK FLOW: the message that is usually your filter

Every JXi has a water pressure switch that won't let the burner fire without circulation, and CHECK FLOW is that switch reporting it never closed. Jandy specifies at least 30 gallons per minute through the heater, up to a 100 gpm maximum, and warns that flow under 30 gpm can cause nuisance operation and even damage the heater. Jandy's remedy list for this message, in order: breakers, wiring, and the time clock; a dirty filter, a blockage, or a valve in the wrong position; return eyeball fittings missing from the pool wall; adjusting or replacing the pressure switch; and turning up a variable-speed pump.

That last one is the South Florida special. Nearly every pad we service runs a variable-speed pump now, and a pump dialed down for savings may not push 30 gpm through the heater when it calls for heat. Raise the speed during heating hours before anyone suspects the switch. If the switch does need adjusting, that's a tech job — Jandy's procedure has the side panel off and the heater running.

FAULT-CHECK IGN CONTROL and the LED flash count

This is the light-off failure, and Jandy's cause list covers air and gas alike: split, pinched, or disconnected air pressure switch tubing; a combustion fan that won't run or runs slow; restricted air at the intake or discharge; a broken igniter; low gas pressure or volume; no flame; and loose wiring. On the LXi, Jandy adds oscillating pump pressure, fixed by cleaning the filter — the one homeowner check on this message.

A tech narrows it down with the LED on the ignition control. Jandy's LED codes read the same on the JXi and the LXi:

• LED on steady: ignition control fault.
• One flash: air flow fault — tubing, fan, or a restriction at the intake or discharge.
• Two flashes: flame exists when there is no call for heat. Jandy says to refer it to qualified service, and I'd leave the heater off until a tech has looked at it.
• Three flashes: ignition lockout — three failed tries to fire. Jandy calls it a soft lockout.

Past the LED it's gas work. Jandy specifies inlet gas pressure of 4.0 to 10.5 inches of water column on natural gas and 4.0 to 14.0 on propane, read with a manometer while the heater is firing — Jandy warns that a reading taken with the heater off can mislead. The manual also says gas valve failures are extremely rare and that the valve should be replaced only after it's confirmed as the root cause. If someone wants to sell you a gas valve first, ask what they measured. When the supply line is the problem, see our gas heater line sizing guide.

FAULT-HIGH LIMIT and FAULT-HIGH FLUE TEMPERATURE

FAULT-HIGH LIMIT means water inside the heater got hotter than its internal limit, or a limit switch faulted. Water overheats in a heater when it isn't moving through fast enough, so flow is the first look here too. Once flow is confirmed good, Jandy's LXi guidance is to verify the high limit switches, run a temperature rise test, and find the cause of the overheating — licensed work.

FAULT-HIGH FLUE TEMPERATURE is a JXi message: the flue temperature limit tripped. Jandy's remedy starts with inspecting the vent for obstructions — on indoor installs it specifically calls out bird, insect, and rodent activity in the vent pipe — and then replacing the flue sensor. A look at the top of the heater from outside is yours. The sensor isn't.

Fix before you call: the homeowner sequence

1. Write down the exact message. Photograph the display and note whether you have a JXi or an LXi — the wording differs.
2. Confirm the heater is being asked to heat. Control in POOL or SPA, set point above the current water temperature — Jandy's own first check before service.
3. Clean the filter and empty the baskets. A loaded filter is the most common reason a heater can't see flow.
4. Walk the pump and valves. Pump running, time clock or automation set correctly, valves to the heater open, return eyeball fittings in the pool wall, and a variable-speed pump fast enough to move 30 gpm through the heater.
5. Clear around the heater. Jandy wants the top, underneath, and surrounding area free of leaves and combustible debris, and the combustion air openings unblocked.
6. Confirm gas at the source. The main gas valve outside the heater jacket open, and on propane, a tank that isn't empty.
7. Restart once. If the same message comes back, stop. Resetting the same fault over and over isn't diagnosis.

One rule overrides the list, and it matters in hurricane country: if any part of the heater has been under water, Jandy says not to use it until a qualified technician has inspected it and replaced any affected control or gas control parts.

Jandy JE and VersaTemp heat pump faults

Jandy's JE and VersaTemp manuals carry the same diagnostic table, and the display holds a fault until the problem is resolved.

• FAULT-NO FLOW. Low or restricted flow — an external bypass valve in the wrong position or a malfunctioning flow switch. Pump running, valves set, filter and skimmers clean, water level up, and any fountain or waterfall that bypasses the heat pump inlet temporarily shut off.
• FAULT-HIGH REF PRESSURE. Head pressure opened the high pressure switch. Jandy's fix is a flow fix: pump on, valves open, filter and skimmers clean, and a higher speed on a variable-speed pump. Cycle the unit off and on up to three times before you call.
• FAULT-LOW REF PRESSURE. Suction pressure dropped, which Jandy notes can happen when the air is cold. Check that the fan runs and air comes out the top.
• FAULT-HIGH WATER TEMP. A safety shutoff when the water reaches the maximum allowed temperature, unless the unit is in chiller mode.
• COIL SENSOR or WATER SENSOR faults (shorted or open). A sensor failed or came disconnected, and the control shuts the heat pump off.

Both manuals also mention a five-minute delay countdown, so a unit that won't start right after it's switched on may simply be waiting it out. Anything past the flow and fan checks is refrigerant or electrical work, and refrigerant work requires an EPA-certified technician.

South Florida failure modes

• Storm debris. One storm can pack the baskets and load the filter at once, which produces CHECK FLOW on a JXi and FAULT-NO FLOW on a JE from a single cause.
• Critters in the vent. Jandy calls out birds, insects, and rodents in vent pipes. On outdoor Florida pads we find wasp nests and spider webs in heaters that sat idle all summer.
• Water chemistry. Jandy's JXi warranty doesn't cover heat exchanger damage from corrosive water, and the LXi warranty excluded scaling that restricts flow. Balanced water is the cheapest heater insurance on the pad.

What repairs cost, and when to replace

Most heater repairs we quote land between $250 and $1,800. A heat exchanger, or a compressor on a heat pump, runs $4,000 to $5,000, and at that number a new heater at $5,000 to $7,000 installed is usually the better buy on an older unit. A diagnostic visit runs $0 to $125, and it's free for our weekly-route clients.

When to call a pro

Flow, valves, the filter, the baskets, and the gas supply valve outside the heater are yours. Everything inside the cabinet — the LED read, igniter, air pressure switch, sensors, limit switches, and gas pressure under load — is licensed work. We manage heater repairs across Palm Beach and Broward under our Florida Certified Pool/Spa Contractor license, doing most of the work ourselves and bringing in a licensed gas contractor for gas line work, or an electrician when a job needs a new circuit. Start with our pool heater repair service, or work the brand-neutral checklist in our pool heater troubleshooting guide first. Running a different brand? See the Raypak, Pentair MasterTemp, and Hayward code guides.