Pentair MiniMax Plus 400 burners won't start

[DenZ]

Hi everyone,

I have an issue with my pool heater Pentair minimax plus 400. I get POWER, TSTAT, AUX, PRESS lights on (green) and service light red. Heat light is off. On the back side all LEDs are green (PVALV, TFUSE, HITEMP). Pilot starts and burns, but the main burner does not start. Control panel gets 24V AC from the transformer. My guess valve does not open, but can't be 100% sure. Based on the manual there should be 24V between the red wire that goes to the valve and the ground, but I only get few volts. Tryingto figre out if it is valve, control pannel or something else. Is there a way to open valve manually to check confirm this is not a flow blockage issue? is there a way to bypass the contorl board and power valve directly to confirm its power board. I assume that since pilot starts and all LEDs are green it can't be ignition board, correct?

 

[1poolman1]

Hi everyone,

I have an issue with my pool heater Pentair minimax plus 400. I get POWER, TSTAT, AUX, PRESS lights on (green) and service light red. Heat light is off. On the back side all LEDs are green (PVALV, TFUSE, HITEMP). Pilot starts and burns, but the main burner does not start. Control panel gets 24V AC from the transformer. My guess valve does not open, but can't be 100% sure. Based on the manual there should be 24V between the red wire that goes to the valve and the ground, but I only get few volts. Tryingto figre out if it is valve, control pannel or something else. Is there a way to open valve manually to check confirm this is not a flow blockage issue? is there a way to bypass the contorl board and power valve directly to confirm its power board. I assume that since pilot starts and all LEDs are green it can't be ignition board, correct?

You should NEVER open a gas valve. Your voltage check should be between the two terminals on the gas valve, MV - MVPV, not to ground.
Also, check the flame sensor, which could be a part of the pilot assembly. The heater may not be sensing that there is a lit pilot. If the pilot flame is up to a "fork" in the assembly, that is the sensor and it needs to be cleaned. This a picture of a pilot assemble (upside-down) that may be in your heater.
Also, be sure any "green" ground wire that is on the main valve and connected anywhere in the cabinet has clean connection areas.

 

[DenZ]

You should NEVER open a gas valve. Your voltage check should be between the two terminals on the gas valve, MV - MVPV, not to ground.
Also, check the flame sensor, which could be a part of the pilot assembly. The heater may not be sensing that there is a lit pilot. If the pilot flame is up to a "fork" in the assembly, that is the sensor and it needs to be cleaned. This a picture of a pilot assemble (upside-down) that may be in your heater.
Also, be sure any "green" ground wire that is on the main valve and connected anywhere in the cabinet has clean connection areas.
View attachment 610147

Thank you a lot. I will double check the voltage between MV and MVPV. Manual does not elaborate much on flame sensor. Does if there is no flame, small flame or sensor is dirty, does it shut off gas to the burner and pilot or only burner? There is only one wire that goes to the pilot from ignition. How does the flame sensor sends signal to the control board, i.e. where to I check signal from the sensor?

 

[1poolman1]

Thank you a lot. I will double check the voltage between MV and MVPV. Manual does not elaborate much on flame sensor. Does if there is no flame, small flame or sensor is dirty, does it shut off gas to the burner and pilot or only burner? There is only one wire that goes to the pilot from ignition. How does the flame sensor sends signal to the control board, i.e. where to I check signal from the sensor?

You would need a meter that test microamps to test the fame sense portion. There are two signals that go down that one wire, the spark and the very tiny current that is looking for the flame to complete the circuit. Flame, ionized gas, conducts electricity. If the system stops sparking, the flame sensor is working and it is probably the grey Honeywell IID device that is not sending current to open the main valve. That's an old heater that hasn't been manufactured in at least 20 years. The IID device is a Honeywell S8600 series device that looks like this: