Pentair MasterTemp Heater Not Igniting Error Codes
- Low water flow, pressure switch open
- Ignition lockout latched
- Gas supply or pressure fault
Problem Description
The Pentair MasterTemp gas pool heater does not ignite when called to heat. The control panel may display error codes, the heater may click without lighting, or the blower may run without gas ignition. MasterTemp heaters use a hot surface igniter (HSI) — a glowing element that lights the gas rather than a spark igniter. The most common failures are the HSI burning out, the flame sensor not detecting the flame, or insufficient water flow triggering the pressure switch.
Why This Happens in Real Homes
A MasterTemp that will not ignite is usually a water-flow or pressure-switch issue, a dirty flame sensor or HSI, or a gas fault, and the panel code narrows it down. In real installs a dirty filter dropping flow trips the pressure switch and blocks ignition.
Confirm flow and gas, reset the lockout, and clean the flame sensor before replacing parts.
Symptoms
- MasterTemp will not ignite
- Control panel shows an error code
- Ignition lockout
- Fires then drops out
- No heat with the pump running
- Clicks but no flame
- Intermittent flame
- Repeated lockouts
Recognize these? Here's what usually causes it.
Common Causes
- Low water flow, pressure switch open
- Ignition lockout latched
- Gas supply or pressure fault
- Dirty or failed flame sensor
- Failed hot surface igniter (HSI)
- Dirty filter cutting flow
- Closed gas valve
- Airflow or venting problem
Most fixes happen in the first 3 steps.
Step-by-Step Solution
Read the error code on the control panel
The MasterTemp display shows specific error codes. The most common: E01 (water temp sensor open/shorted — bad thermistor), E02 (water temp limit exceeded — check flow), E05 (stack flue sensor tripped — exhaust too hot from restricted flow), E06 (ignition lockout — 3 failed ignition attempts), AGS (auto gas shutoff after flame failure). Press any button to clear the error, then attempt to restart. If E06 repeats, the igniter, flame sensor, or gas supply needs troubleshooting. The full error code list is on page 16 of the MasterTemp service manual.
Verify water flow and pressure switch
The MasterTemp will not attempt ignition unless the pressure switch detects adequate water flow. The pump must be running and the filter must not be dirty. Check filter pressure — if above 25 PSI, backwash or clean the filter. Open the heater front panel and locate the pressure switch (a small disc with two wires on the water header). With the pump running, you should hear the switch click closed. If it does not click, water flow is too low or the switch is faulty. Disconnect one wire and test with a multimeter — it should show continuity when the pump runs.
Inspect the hot surface igniter (HSI)
Turn off gas and power to the heater. Open the front access panel. The HSI is a thin silicon carbide rod positioned inside the burner assembly — it glows orange-hot to ignite the gas. Remove the two screws holding the HSI bracket and gently pull it out. Inspect the element — if it is cracked, broken in two pieces, or has visible fracture lines, it is burned out and needs replacement. Do not touch the HSI element with bare fingers — skin oils cause hot spots that shorten its life. Handle by the ceramic base only. Pentair HSI part number is 42001-0052S.
Clean or replace the flame sensor
The flame sensor is a separate rod near the HSI that detects whether the gas actually ignited. If the flame sensor is coated with carbon or corrosion, it cannot detect the flame and the control board shuts off gas within 7 seconds of ignition (AGS error). Remove the flame sensor (one screw, one wire connector) and clean the rod with fine sandpaper (400 grit) or steel wool until the metal is shiny. Reinstall and test. If the heater ignites but shuts off after 5-7 seconds, the flame sensor is still the issue — replace it. Part number 42001-0063S.
Check gas supply and pressure
Confirm the manual gas shutoff valve is open (handle parallel to pipe). If using propane, check that the tank has fuel. The MasterTemp requires specific gas pressure: 3.5 inches water column (IWC) for natural gas, 10 IWC for propane at the heater inlet. Low gas pressure causes the heater to ignite weakly and then trip the flame sensor. If multiple gas appliances run simultaneously (pool heater + house furnace + dryer), gas pressure at the heater can drop below the minimum — a gas line sizing issue that requires a plumber.
Reset the ignition lockout
After three failed ignition attempts, the MasterTemp enters ignition lockout (E06) and stops trying. To reset, turn the heater off using the On/Off button on the control panel, wait 30 seconds, then turn it back on. If lockout keeps recurring, the underlying cause (bad HSI, dirty flame sensor, gas issue) must be fixed first. Do not repeatedly reset lockout without diagnosis — the control board limits lockout resets as a safety measure and may require a full power cycle (breaker off for 60 seconds) after multiple lockouts.
Quick Solutions
Still having issues? This is usually the deeper cause below.
If the keypad rejects valid codes, a lockout timer may be running — five failed entries locks most keypads silently for 5–10 minutes.
The Pentair MasterTemp installation and service manual is at https://www.pentair.com/content/dam/extranet/residential-pool/manuals/mastertemp-heater-installation-guide.pdf — it includes all error codes, wiring diagrams, igniter access, and gas pressure specifications. The hot surface igniter lasts 3-5 years on average. Keep a spare on hand (part 42001-0052S) so you are not waiting for a part when the heater fails on a cold weekend. Gas-side work (gas valve, gas piping) should be done by a licensed technician.
This issue almost always looks more complex than it is — the majority of cases trace back to a single setting, a stale credential, or a default that shipped wrong.
- Low water flow, pressure switch open
- Ignition lockout latched
- Gas supply or pressure fault
- Dirty or failed flame sensor
- Failed hot surface igniter (HSI)
Before you go — try one of these (they fix most cases).
Official Manufacturer Manual
Pentair provides official product documentation through their online manual rather than downloadable PDF. Access setup guides, troubleshooting steps, and product specifications for your Pentair MasterTemp Pool Heater.
Source: pentair.com
Need More Help? Pentair Support
Note: The contact information below connects you directly to Pentair's official customer support team, not Trunetto. They can help with warranty claims, device replacements, and advanced technical issues.