Troubleshooting guide
Pool heater won't fire
Gas pool heaters have a water pressure or flow switch that must close before the burner can light. A dirty filter or low pump speed is the most common reason a heater just sits there.
If you smell gas, stop
Safe checks you can do
- Is the pump running fast enough? Jandy lists "variable speed pump set too low" as a cause of CHECK FLOW. Run the pump at a higher speed while you test.
- Clean filter, clean baskets. Pentair's MasterTemp guide says restricted flow can keep the burner from firing, and if the light stays on after the filter has been serviced, a qualified tech should check the pressure switch.
- Valves. Make sure the valves to and from the heater are open and the returns aren't blocked.
- Settings. Is the heater on, set for the right body of water (pool or spa) and set above the current water temperature? If automation controls the heater, check it's calling for heat.
What the common codes mean
| Heater | Flow / pressure | Ignition |
|---|---|---|
| Pentair MasterTemp | ERR PS: water pressure switch open. Clears when flow returns. | ERR IGN: the ignition module couldn't light the heater. Press HEATER OFF to clear. |
| Hayward Universal H-Series | LO: water pressure switch, vent pressure switch or temperature limit switch fault. | IF: ignition failure. Retries 3 times, locks out, then retries every 60 minutes. |
| Jandy JXi | CHECK FLOW: pump not running, low pump pressure or pressure switch fault. | CHECK IGN CONTROL: air, fan, igniter, gas supply or no flame. |
Full lists: Pentair, Hayward and Jandy codes.
When it's a tech job
Don't bypass a pressure switch (Pentair's manual warns against it). If flow is good and the code stays, or you see ignition, high-limit, flue or sensor codes, the next steps involve gas, high voltage or combustion parts. A tech on video can confirm what the heater is telling you and which part it points to before anyone orders one.
Common questions
Why won't my pool heater turn on?
The most common reason is not enough water flow: a dirty filter, full baskets, closed valves or a variable-speed pump set too low. Gas heaters won't fire until their pressure switch sees enough flow. Check those, then check the heater's settings and any code on its display.
What does ERR PS mean on a Pentair MasterTemp?
ERR PS means the water pressure switch is open: there isn't enough water flow through the heater. Pentair says the error clears and the heater resumes once flow is established.
Can I bypass the pressure switch to test my heater?
No. Pentair's manual warns not to bypass the water pressure switch or make it inoperable. It's a safety device. Have a qualified tech test it if flow is good and the code stays.
Related guides
Pentair error codes
MasterTemp ERR PS, HLS, IGN, AGS; IntelliFlo3 alarms; IntelliChlor lights.
Read the guideHayward error codes
Heater LO, IF, HS, AO; MaxFlo VS Check System messages; AquaRite lights.
Read the guideJandy error codes
JXi CHECK FLOW, HIGH LIMIT, CHECK IGN CONTROL and the ignition LED flashes.
Read the guideFilter pressure high or low
The gauge tells you when to clean the filter, and when something upstream is wrong.
Read the guideSources
- Pentair, MasterTemp pool and spa heater installation and user's guide: safety controls and Table 8, heater error and fault codes
- Hayward, Universal H-Series heater troubleshooting guide (UHS16b): diagnostic codes and failure-to-light sequence
- Jandy (Zodiac), JXi gas-fired pool and spa heater installation and operation manual (H0574300): service diagnostic messages and ignition control LED codes
Brand names belong to their owners. Pool Helpline isn't affiliated with or endorsed by any manufacturer. Steps and codes vary by model and year, so always check your own owner's manual.
Parts & supplies for this fix
Hayward Filter Cartridge - Fits C2030 Filters (CX481XRE)$108.99 · free shipping
Waterway Air Relief Plug 715-1001$12.99 + $8.99 shipping
Hayward Filter CX470XRE Cartridge - Filbur (APCC7648)$98.99 + $10.99 shipping
Super-Pro Pool Filter Pressure Gauge Steel Bottom Mount 1/4" 0-60 PSI (83060BU)$27.99 + $10.99 shipping