Pentair mastertemp 400 shutting down after hitting 289

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JamesW said:

Pentair Membrane Key Pad Replacement.​

The membrane keypad sometimes fails and is separately replaceable with Pentair part number 472610Z for the five button keypad used on the non-connected heater version.

To replace the membrane keypad peel the old one off, clean the area as best you can, stick on the new keypad. Be sure to align the openings for the service lights. Also, push the ribbon cable all the way through before removing the protective paper or it can get stuck to the membrane.

If a single button on the keypad is not working it may be due to corrosion on the pins of the membrane keypad ribbon cable. Cleaning any dark pins with emery cloth may get the keypad working.[38]

The following applies to the 5 button keypads found on the older MasterTemp heaters. Pin 1 is the common wire. Shorting pins 1 to 2 briefly is the same as pressing "Spa On". Pressing a button on the membrane pad shorts a pin (2 through 5) to pin 1 to make a selection. Pin 1 is the lowest pin and pin 6 is the highest pin.[39]

  • 1 to 2 ...spa on.
  • 1 to 3...pool on.
  • 1 to 4...heater off.
  • 1 to 5...down arrow.
  • 1 to 6...up arrow.
You can briefly short the pins as listed above to simulate pressing a button but don't leave the pins shorted.

The pins are so small and close together that it's hard to short any two without touching the others. So don't do it if you can't short only two.

If you can short only a single pin to pin one, the board should respond as indicated. If it doesn't, then the control board is bad. If all pin combinations work by short but not by pad buttons then the membrane is bad.
View attachment 618697
Click to expand...
thank you I will try that
 
As soon as you see "Service Heater" you need to check the Fenwal and the back of the control board for error LEDs.

Check the flame current and the gas pressure.

Heater Flame Sensing - Further Reading

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The Fenwal has two test points for flame current FC+ and FC-.

The best way to measure the flame sense current is with a true RMS meter.

Measure the current with a good true rms meter that can measure dc current in the microamp range.

To measure flame current, connect a True RMS or analog DC micro-ammeter to the FC+ and FC- terminals.

Readings should be 1.0 µA DC or higher.

If the meter reads negative or below "0" on scale, meter leads are reversed. Reconnect leads with proper polarity.

If you don't have a RMS meter you can just test for voltage between FC+ and FC- terminals to confirm if you have flame sense.

Each micro-amp of flame current produces 1.0 VDC.

For example, 2.6 VDC equates to 2.6 µA.

Voltage is an indirect indication but easier to do with typical DIY equipment.

But it's still very difficult to measure unless you make up some pin wires to clip your voltmeter to.

Or you can order some insulated micro clips for the test.

The reading should be 3-8 volts and this corresponds to the millionth's of an amp signal your flame sense signal should reading.

If you try to check this be very careful since you can easily short the 24 vac circuit which can blow the transformer before the 2 amp fuse blows.

When not operating, the flame current should read 0 volts dc and 0 microamps dc.

DC amps and voltage should be zero when there is no flame.[6]


1732400582801.png
 

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The following are the LEDs:
  1. .....PS (Pressure Switch)
  2. .....HLS (High Limit Switch)
  3. .....SFS (Stack Flue Sensor)
  4. .....AFS (Air Flow Switch)
  5. .....AGS (Automatic Gas Shutoff).
  6. .....Service System
  7. .....Thermistor
  8. .....Heating
  9. .....Pool On
  10. ...Spa On
  11. ...Service Heater.
If it was one of these errors, the heater would not try to relight.

Since the heater tries to relight, the problem is most likely a loss of Flame Rectification.

This should produce a 3 flash LED on the Fenwal to indicate Ignition Lockout.

Maybe the LED does not work correctly.

In any case, check the Flame Current.

If it is low and erratic, then the ground wires might be bad or maybe there is a loss of flame due to low gas pressure.

Clean any ground wires and check the gas pressure.

 

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If you get a Service Heater light, then the heater is going to give a reason at the Fenwal or the board.

Maybe the Fenwal Led is burned out.

The following are the LEDs:
  1. .....PS (Pressure Switch)
  2. .....HLS (High Limit Switch)
  3. .....SFS (Stack Flue Sensor)
  4. .....AFS (Air Flow Switch)
  5. .....AGS (Automatic Gas Shutoff).
It is not the Pressure Switch because that would give a Service System Light (vs. Service Heater).

It is probably not Stack Flue Temp because the Stack temp is showing in normal range.

It is probably not HLS (High Limit Switch), AFS (Air Flow Switch) or AGS (Automatic Gas Shutoff) because the heater would not try to relight.

In my opinion, it is probably a loss of Flame Rectification, which might be due to a weak flame or a bad ground.

The Stack temp would be low with a weak flame, so I suspect that the issue is a bad ground.

Did you check the flame current and the gas pressure?

Did you clean the ground wire connection?
 
JamesW said:
If you get a Service Heater light, then the heater is going to give a reason at the Fenwal or the board.

Maybe the Fenwal Led is burned out.

The following are the LEDs:
  1. .....PS (Pressure Switch)
  2. .....HLS (High Limit Switch)
  3. .....SFS (Stack Flue Sensor)
  4. .....AFS (Air Flow Switch)
  5. .....AGS (Automatic Gas Shutoff).
It is not the Pressure Switch because that would give a Service System Light (vs. Service Heater).

It is probably not Stack Flue Temp because the Stack temp is showing in normal range.

It is probably not HLS (High Limit Switch), AFS (Air Flow Switch) or AGS (Automatic Gas Shutoff) because the heater would not try to relight.

In my opinion, it is probably a loss of Flame Rectification, which might be due to a weak flame or a bad ground.

The Stack temp would be low with a weak flame, so I suspect that the issue is a bad ground.

Did you check the flame current and the gas pressure?

Did you clean the ground wire connection?
Click to expand...
I cleaned the ground wire connection. Still same problem. I just bought a true rms multimeter so I'll check the flame current soon. It's a cheap one though 20 bucks. And check gas pressure. Thank you for your guidance.
 
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I had the same problem years ago on the same model Pentair Heater. The SF temp would reach a certain point and then go into service heater alarm. Eventually I found a large mouse nest inside the heater. The mice had chewed through the wire insulation and several wires were touching together. I spliced around the defective area and everything ran fine after. I hope you are as lucky as I was.
 
Sodium Chloride said:
I had the same problem years ago on the same model Pentair Heater. The SF temp would reach a certain point and then go into service heater alarm. Eventually I found a large mouse nest inside the heater. The mice had chewed through the wire insulation and several wires were touching together. I spliced around the defective area and everything ran fine after. I hope you are as lucky as I was.
Click to expand...
Thank you I will look for that
 
JamesW said:
If you get a Service Heater light, then the heater is going to give a reason at the Fenwal or the board.

Maybe the Fenwal Led is burned out.

The following are the LEDs:
  1. .....PS (Pressure Switch)
  2. .....HLS (High Limit Switch)
  3. .....SFS (Stack Flue Sensor)
  4. .....AFS (Air Flow Switch)
  5. .....AGS (Automatic Gas Shutoff).
It is not the Pressure Switch because that would give a Service System Light (vs. Service Heater).

It is probably not Stack Flue Temp because the Stack temp is showing in normal range.

It is probably not HLS (High Limit Switch), AFS (Air Flow Switch) or AGS (Automatic Gas Shutoff) because the heater would not try to relight.

In my opinion, it is probably a loss of Flame Rectification, which might be due to a weak flame or a bad ground.

The Stack temp would be low with a weak flame, so I suspect that the issue is a bad ground.

Did you check the flame current and the gas pressure?

Did you clean the ground wire connection?
Click to expand...
7.6 volts AC for FC with heater off. When I flip the breakers to off its 0.0 which is expected.
 

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