The Pentair Mastertemp 400 is a powerful pool heater -when it works as it should. However, there are a couple of instances where you may experience problems while using it.
It can be frustrating trying to identify and troubleshoot malfunctions in your Pentair Mastertemp 400. Therefore, our team has compiled a list of the common problems with the pool heater and how you can troubleshoot them.
Let’s get to it. Starting with the error codes.
The Pentair Mastertemp 400 error codes
Here’s a list of all codes you may encounter while using the Pentair Mastertemp 400.
1. ERR AGS: Automatic Gas Shutoff
When you see the AGS error code, the gas flow has shut off because of a low flow rate or a damaged pressure switch. To troubleshoot, start by checking if the water flow rate meets the minimum requirement for a heater. If it’s below the minimum, service the pump and filter, then confirm the right operation of the Pressure Switch.
Next, confirm the flow rate is okay, and the water temperature is below 104 degrees F. If it’s above, you must replace the thermistor or control board to stop the overheating. Ultimately, you can replace the AGS.
Also, verify the Internal Bypass Valve and the thermal governor are in top shape and that there’s no blockage in the Heat Exchanger.
2. ERR HLS: High Limit Switch
The HLS error code appears when the water flow rate is below the set minimum for a heater and the water temperature goes above 104 degrees F.
The best solutions include; servicing the pump and filter and replacing the thermistor or control board. If you don’t see any change get a new HLS.
3. ERR PS: Pressure Switch
This error code is triggered by an open pressure switch and water overflow. Correct the water flow rate by servicing the pump and filter to fix it. Next, check the wiring and clear any blockage from the pressure tap.
If nothing works, replace the Pressure Switch and adjust it to close while the pump runs and open while it is off.
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4. ERR AFS: Air Flow Switch
If the system hasn’t attained perfect airflow after one minute of a startup, the heater turns off automatically, and the AFS error shows up on the display.
To fix, verify that the blower works, then clear any blockage in the blower intake, exhaust, and heat exchanger. Also, the exhaust shouldn’t be too long.
Next, ensure the wiring and connection of pressure taps to AFS is solid and that the connection of vinyl tubing to AFS and blower isn’t punctured, bent, disconnected, or misrouted.
Lastly, check all the blower wiring and correct the faulty ones. From the line voltage between pins 1 and 3 of the blower connector on the ignition, try the wires BM and F1, and connect between 24VAC and IND terminals on the ignition control board.
If the code persists, replace the AFS, blower, or ignition control board.
5. ERR SFS/E05: Stack Flue Sensor
Does the heater run normally after you turn it on, but then the exhaust temperature shoots to 450F- 500F within 3-5 minutes? Does it start after many tries only for the exhaust temperature to stagnate at 250F or below? Or does it not start at all?
These issues trigger the SFS code, and they are caused by an incorrect fuel supply or a faulty thermal regulator.
To solve the problem, ensure the heat exchanger coil has no leaks, soot, liming, or low flow. Next, confirm the thermal regulator is positioned properly. Thirdly, correct the pressure and volume of the fuel supply.
You may disconnect the sensor and inspect its continuity across its terminals. The resistance is supposed to be 3.5-4.0 mega ohms.
Also, inspect the J3 and J6 connections for corrosion or looseness. If the error doesn’t go away after troubleshooting, you should replace the heater membrane pad, heater control board, and the SFS.
You can replace them in succession while checking if the error disappears. Remember to reset the power to the heater after every replacement.
6. ERR IGN: Ignition Control Module
You’ll see this error code when the Ignition control module doesn’t ignite the heater. To fix it, you must ensure the burner is okay.
First, open the burner and remove anything that might be blocking it. Next, confirm that it’s secured with gas and other lines. If the burner has significant damage, replace it with a new one.
7. E01/126: Temperature Sensor is Open
The water temperature sensor is faulty if you see either of the two error codes on your Pentair Mastertemp 400 display. That could be due to damaged wiring or thermostat. Check the two and consider replacing them.
The Pentair Mastertemp 400 pool heater keeps shutting off
When the heater shuts off when you turn it on, and there is no error code to notify you what or where the problem is, you can reset the system so that it starts afresh. Here is how to use the Pentair Mastertemp 400 reset button:
- Open and turn the underside of the control panel board.
- Press the yellow button on the corner.
- Press the temp pad to set the maximum pool temperature.
- Wait for 30 seconds.
- Press the temp pad again and set the max temperature to 1040 F or lower.
- Wait for 30 seconds.
- Power on your heater to see if the problem is gone.
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The Pentair Master temp 400 burner issues
The burner has a long exhaust vent if it pulsates or surges on the ignition. To solve it, shorten the length of the exhaust vent and the number of elbows.
Other issues with the burner include:
A loud, high-pitched whine
You’ll hear this noise when the flame is too rich. To troubleshoot, start by confirming the pressure tap between the gas valve and blower inlet. The regulator setting should be -0.2” (-0.5cm) wc. Next, get a certified technician to replace the gas orifice.
The flame doesn’t stay lit even though the combustion seems normal
This happens when the flame current isn’t sensed. To fix it, look for a wet or damaged igniter and replace it with a new one. Secondly, ensure the burner flame holder is grounded properly. Lastly, replace the ignition control module.
The flame is fluttery, the burner doesn’t stay lit, and the exhaust has an acid smell
You will encounter these burner problems when the flame is too lean. The best way to troubleshoot is to confirm the gas regulator setting is -0.2” (-0.5cm) wc. Call a qualified technician to replace the gas orifice if it’s not.
The thermistor
When your thermistor has a problem turning on, check the wiring. If the connection is fine, replace the thermistor.
The Pentair Master temp 400 heat exchanger
When you discover boiling in the heat exchanger characterized by “bumping” sounds, there’s likely low water flow to the heater, the thermal governor is stuck closed, or the bypass valve is open. The solutions include servicing the pump and filter, replacing the thermal governor, and servicing the heat exchanger and bypass valve.
Another symptom of a failing heat exchanger is sweating. A faulty thermal governor causes it, and the best solution is to get a new thermal governor.
You should also check the heat exchanger for signs of corrosion. Immediately you notice the parts are corroding, prepare to get another heat exchanger even before the heater starts acting up.
The red diagnostic LED’s on the back of the board are not on
Switch off the power to the heater for a few seconds, then switch it back on. Ensure the temperature is set above the water temperature. Wait for at least a minute to see if the LEDs turn on.
If the LED’s come on but doesn’t stay on, check if the red “SERVICE HEATER LED” is on. If it’s not, confirm the water temperature is set above the water temperature reading. Are the settings okay, but the LEDs won’t turn on, and the heater doesn’t fire, then it is time to replace the control board.
Pentair Mastertemp 400 service heater light is on
When facing this problem, ensure your temperature setting is above the water temperature. Then, turn off the heater power, wait for 5 seconds and turn it back on. If the heater’s power stays on, continue observing its behavior for several minutes to be sure it won’t malfunction again.
Additionally, confirm the burner is firing. If it’s not, verify the status of the blower. In case it’s not responding, replace the control board. But, if the blower is okay, ensure the gas supply and flow are seamless. Don’t hesitate to replace damaged gas valves that are leaking.
The red Service System LED is on
This could be because of filter blockage, minimum water flow, or pump issues. Your first solution is to service the pump and filters and remove any blockage.
Also, adjust the water pressure switch downwards until the service system LED turns off. The minimum flow requirement for the Pentair Mastertemp model 400 is 40gal/min (151 LPM).
The green SPA or Pool LED is off
The absence of these LED lighting means the line voltage to the heater has a problem. To correct it, you must ensure the 12-pin plug is installed correctly (red 240V and clack 120V).
Also, you’ll have to check the wiring connections between the power supply and junction box, the junction box and terminal board, and between the terminal board and transformer primary. Restore continuity wherever there’s a fault.
If the wiring is okay and you still have the problem, replace the transformer.
The gas flows during ignition try, but your burner doesn’t fire
In this case, the problem could be the voltage across igniter leads or the gas pressure. For the former, you must replace the ignition control module to fix the gas pressure. You’ll need a large gas line and replace the meter and/or regulator.
Pentair Mastertemp 400 display is not working
The key factors that can lead to the display failure are a damaged display board and switch. However, other issues like disrupted connection, poor water flow, and faulty ignitor can also trigger or worsen the situation.
To troubleshoot the problem, you can check and replace the display board and the controller fuse, turn off the by-pass valve so that water passes through the heater, repair or replace the ignitor, unplug the heater then plug it back after a few minutes.
Maintenance of your Pentair Mastertemp 400
To avoid troubleshooting the Pentair Mastertemp 400 every time it develops a complication, regular schedule maintenance. This will help identify minor issues before they escalate and stall the heater’s performance. It’s recommended to do the maintenance every 6 months at the start of each swimming season.
Here are some of the factors you should check:
- Test the function of the pressure relief valve.
- Check the heater panels and venting system. Remove any obstructions that prevent ventilating air flow, burner exhaust, or room air.
- Ensure there are no combustible materials, gasoline, or corrosive liquids near the heater.
- Test the water pressure switch.
- Inspect the joints for signs of leakage, check the pipes for cracks or breakage, and ensure the combustion air blower is well-lubricated.
- You can curb corrosion of the heater’s parts by maintaining balanced water chemistry in your pool and installing a corrosion-resistant positive seal check valve between the chlorinator and the heater. Also, test the water regularly and ensure the chlorine residual doesn’t fall below 0.6 ppm.
To ensure the maintenance is done properly, get a professional technician to check the entire system. They’ll know what to look for, where, and how to fix underlying issues.
Conclusion
Hopefully, these troubleshooting solutions will help you to fix your Pentair Mastertemp 400 issues. If there are other underlying issues, share them in the comment section, and we’ll address them.