New Max-E-Therm 400 won't fire up

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Terry D.

Member
Jan 26, 2023
16
Florida
Just installed a new Max-E-Therm 400 to replace an old one. This new one has only one LED, which blinks red as it tries to fire up. It keep cycling this startup attempt, but doesn't fire. I thought maybe it was insufficient natural gas supply so bumped it up from 7 inch to 10 inch water column (it is supposed to operate at 4 to 14 inch), measured in the supply line after the regulator. Does the gas valve have to be purged of air?
My old one had several LED's and a red digital message display. All the troubleshooting guides refer to LED's for the pool button, the spa button, etc. This new one has only the one LED and the display is LCD like a calculator display. The old red LED digital display was easier to read but maybe not as reliable?
 
Welcome to TFP.

There is an ON/OFF slide switch on the gas valve that may have been left in OFF on the install.

Is this a NG heater or propane?
 
It can take a few starts to purge the air in the gas line.

A NG heater will try to light 3 times before it gives an Ignition Failure.
 
Terry D. said:
I will let it try to start a few more times. I am not smelling gas. Just wondered if the valve should be bled of air.
Click to expand...
No need to "bleed" a gas valve, especially on a Max-E-Therm, the blower is actually pulling gas through the valve. You should smell a little bit of gas each time the heater lights, that's normal. Do you hear a "click" at anytime in the cycle? That would be the gas valve opening. As was mentioned before, the switch on the valve may still be in the "off" position.
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1poolman1 said:
No need to "bleed" a gas valve, especially on a Max-E-Therm, the blower is actually pulling gas through the valve. You should smell a little bit of gas each time the heater lights, that's normal. Do you hear a "click" at anytime in the cycle? That would be the gas valve opening. As was mentioned before, the switch on the valve may still be in the "off" position.
View attachment 470761
Click to expand...
The blower is on, the red Heating LED blinks on and off, the LCD screen shows SPA temp at 68 and set to 98. After about ten seconds, there is a click and the blower shuts off and the blinking red light shuts off. After about 20 seconds, the cycle starts again - blower, flashing red light, etc. Unlike my old 400, there do not appear to be multiple LED's. Maybe the touch buttons are backlit, but I don't think so. The only LED that lights up on the underside of the main board is the red "Heating" LED. Here are two pictures: One is with the Heating light blinking and the other is after it clicks and shuts off.
 

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AFS- Air flow switch. Check the tubing of the airflow switch to make sure they are all well seated on the barb connectors of the afs and blower cap.

What is the voltage going into the heater?

Further reading:

AFS Error​

AFS is the air flow switch that senses if the blower is on and there is sufficient air flow to the burner. Sequence is blower motor should turn on, AFS senses air flow through a white tube down by the burner can, and switch closes to start the ignition sequence.

You can gently blow into the white tube and you should hear the click of the air flow switch turning on. Check the white tube for cracks or breaks. The white tube is not available as a separate part and comes with the Pentair MasterTemp & Sta-Rite Max-E-Therm Air Flow Switch assembly P/N 42001-0061S.

If you hear the air flow switch closing then check the continuity of the air flow switch relay using a multimeter. Connect the multimeter to the two contacts on the air flow switch after removing the heater wires. You should see it electrically open when no air is blown into the switch and closed when air pressure is through the tube.
 

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Poolbreh said:
View attachment 470780
Click to expand...
There is so much much noise from my pool pump nearby that I am not sure what I should be hearing. Blew in the tube softly and then harder and didn't hear anything, but there definitely is a noticable click when the red heating light and blower shut off. There is no smell of gas. Could there have a plug inside the threaded gas inlet that I didn't notice when I hooked up the gas which might be blocking the gas supply?
 
With an AFS error the heater never gets to opening the gas valve in the startup sequence.

You have the new “connected” heater model. The LED diagnostics that were on the back of the board are now displayed on the screen and sent by RS-485 to the IntelliCenter.

From Pentair MasterTemp Heaters - Further Reading

A running change to all Pentair MasterTemp & StaRite Max E Therm heaters, took place on the afternoon of 5/7/2021.

All heaters made before 5/7/2021 have membrane keypads with five buttons, which identifies them as “Non Connected” models.

Connected Heater Features:

  • RS485 connection to IntelliCenter Automation
  • Upgraded menu structure: Flame strength indicator, Runtime, Cycle Count, Error Code Log
  • Ability to control an external bypass valve
  • Six button membrane keypad
There are significant parts changes with the "Connected Heater" that the Pentair MasterTemp & StaRite Max E Therm : Parts Matrix for “Connected Heater” Update May 2021 lists.

Different parts between heater versions include:

  • PCBA
  • Membrane Keypad
  • Ignition Control Module - ICM -Fenwal box
  • Wiring Harness
  • Bypass Valve Kit
 
Terry D. said:
There is so much much noise from my pool pump nearby that I am not sure what I should be hearing. Blew in the tube softly and then harder and didn't hear anything, but there definitely is a noticable click when the red heating light and blower shut off. There is no smell of gas. Could there have a plug inside the threaded gas inlet that I didn't notice when I hooked up the gas which might be blocking the gas supply?
Click to expand...

No, With an AFS error the heater never gets to opening the gas valve in the startup sequence.

If you had a gas flow problem you would get an IGN error.
 
Put a multimeter on the Air Flow Switch and check for continuity and that the switch closes when you blow into the tube if you don’t hear it click.

With supply chain issues component quality has dropped and more problems are being found in installations.
 
You have the new “connected” heater model. The LED diagnostics that were on the back of the board are now displayed on the screen and sent by RS-485 to the IntelliCenter.
Can I run this heater from the panel like I did my old one?
ajw22 said:
You have the new “connected” heater model. The LED diagnostics that were on the back of the board are now displayed on the screen and sent by RS-485 to the IntelliCenter.

From Pentair MasterTemp Heaters - Further Reading

A running change to all Pentair MasterTemp & StaRite Max E Therm heaters, took place on the afternoon of 5/7/2021.

All heaters made before 5/7/2021 have membrane keypads with five buttons, which identifies them as “Non Connected” models.

Connected Heater Features:

  • RS485 connection to IntelliCenter Automation
  • Upgraded menu structure: Flame strength indicator, Runtime, Cycle Count, Error Code Log
  • Ability to control an external bypass valve
  • Six button membrane keypad
There are significant parts changes with the "Connected Heater" that the Pentair MasterTemp & StaRite Max E Therm : Parts Matrix for “Connected Heater” Update May 2021 lists.
Click to expand...
Can I still run the heater from the control on the top of the heater or do I need some remote panel?
 
Terry D. said:
Can I run this heater from the panel like I did my old one?
Click to expand...

Yes, runs the same just with better diagnostics that you don’t have to open up the top to see.

Terry D. said:
Can I still run the heater from the control on the top of the heater or do I need some remote panel?
Click to expand...

Yes, controls are the same.
 
ajw22 said:
Put a multimeter on the Air Flow Switch and check for continuity and that the switch closes when you blow into the tube if you don’t hear it click.

With supply chain issues component quality has dropped and more problems are being found in installations.
Click to expand...
AFS works, so will go from there with the multimeter checking components. Thanks for the help, everyone.
 
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What is the input voltage?

Usually a new heater with an AFS problem is a 120 volt input with a 230 volt plug installed.

This is because the blower is not spinning fast enough (Due to low voltage) to create enough air flow to trigger the air flow pressure differential switch.

The heater comes with the 240 volt plug installed.

Note: Do Not change the plug without being 100% sure.

If you install the 120 volt plug with 230 volt supply, you can destroy the heater.

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