MasterTemp 300

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R

rookies

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Sep 21, 2022
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ca
Pool Size
20000
Surface
Plaster
Chlorine
Salt Water Generator
Hello, Looking for any help! My 14 year old Mastertemp 300 heater keeps stopping around 85 degrees on the unit...my screen logic and easytouch read about 75 degrees, always 10 degrees cooler (I believe this is more accurate)

Pentair told me to replace the thermistor first then the control board. I looked at the thermistor and saw rusty bolts to the manifold, tighten up the bolts and replaced the thermistor and no change. Saw more seepage and tried to tighten up the thermistor then the plastic insert where the thermistor screws into broke....so now I need a new manifold... This is 1 issue...

Issue 2 is why the heater temp is running too high...I also checked the back of the control board and found red lites on LED 2, LED 5, and LED 11....Im having some problem fining out what exactly those are. I can replace the control board but not sure this would solve my issue.... and suggestions?

Thanks in advance!
Troy
 

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JamesW said:
Click to expand...
Thanks! Im trying to figure out if I piece this 14 year old heater together or bite the bullet and purchase a new one....so, theoretically if I replace the AGS and HLS, along with a new manifold, this control board should be fine....any experience on how long these units last?

Thanks again!
 
Just heard back from pentair...they are telling me:

LED 2 is Pressure Switch
LED 5 is Stack Flue Sensor
LED 11 is communication issue between control board and ignition control module.

There is a possibility that I have misread the LED lights on my control board....

Anyway some of you can take a look at the pics and see if the above are the problem....They dont match up to James numbers, but I may have misread my lights...
Thanks!
 

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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.
As you can see on your board, all of the LEDs for errors are labeled with the two or three letter codes.

LED 11 lines up with the Membrane pad display window for Service Heater.

LED 6 lines up with the Membrane pad display window for Service System.

LED 8 lines up with the Membrane pad display window for Heating.

LED 10 lines up with the Membrane pad display window for Spa On.

LED 9 lines up with the Membrane pad display window for Pool On.

You have to reverse the membrane because you are looking from the back.


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The old control board was replaced by the new Connected Heater control board p/n 461105.

The new Control Board Kit 461105 comes with "6 button" membrane keypad.

The new circuit board is different and it only has a Heating LED displayed through the Membrane Pad window.

Maybe Pentair was referring to the newer version of the board for the LED indicators?
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Thanks James....I will be receiving my manifold fri....and I will also order and install the following:

AGS switch (led 5)
HLS switch (led2)
Thermal regulator (led 11)

Thanks again for clarifying this and all the help!
 
Most likely, the problem is overheating due to a bad thermal regulator.

Remove the thermal regulator and see how it runs.

Check the stack flue temperature.

Exhaust Gas Temperature.​

While running, press and hold the On button to display the exhaust temperature (Older Models).

The new models use the Menu to get the SFS.

Here is what the normal exhaust temperature should be:
  • Below 250 degrees...very low
  • 250 to 290 ..................low
  • 290 to 350.................acceptable
  • 350 to 480 ..................high
  • Above 480...................error/shutdown.
Note: HD models can be up to 75 degrees higher. HD models use a cupro nickel exchanger and the efficiency is slightly lower resulting in less heat transfer and more waste heat.

If the exhaust gas temperature is higher then normal then water may be bypassing the heat exchanger through a broken bypass valve.

If you hold down the "pool on" button, it stays on 80, then flashes to 40, then back to 80, then the 80/40 reading and E05 indicate that the board is not getting a reading from the sensor. It's usually a bad sensor or damaged wires.

https://www.troublefreepool.com/wik...ir_MasterTemp_Heaters#Exhaust_Gas_Temperature

https://www.troublefreepool.com/wiki/index.php?title=Pentair_MasterTemp_Heaters#AGS_Error

https://www.troublefreepool.com/wiki/index.php?title=Pentair_MasterTemp_Heaters#Thermal_Regulator

https://www.troublefreepool.com/wik...emp_Heaters#HLS_.28High_Limit_Switch.29_Error

https://www.troublefreepool.com/wiki/index.php?title=Pentair_MasterTemp_Heaters
 

HLS (High Limit Switch) Error.​

The High Limit Switch prevents the Heat Exchanger outlet temperature from exceeding 135°F (±8°F).

The High Limit Switch is located in the lowermost well of the Manifold Adapter under the Manifold Switch Cover. Mounted below the AGS Switch, it is black to differentiate it from the AGS Switch, which is marked with a red dot.

The HLS is often caused by lack of sufficient water flow through the heat exchanger. This can be due to several things:

  • Thermal regulator not opening.
  • External bypass open.
  • Internal bypass broken.
  • Pump too small or on too low rpm.
  • Clogged filter.
  • Scale in heat exchanger.
The High Limit Switch is p/n 42001-0063S

Start by checking the thermal regulator.
 
James....great info and I will run those tests once Im able to start the heater, water sprays all over now due to a cracked manifold...

I never did get any error codes, just saw the red LED lites on back of board....

I will check the thermal regulator today.

The manifold I bought comes with all installed new switches, just not a thermal reg, but I ordered that already...
 
rookies said:
Thermal regulator (led 11)
Click to expand...
LED 11 is Service Heater, which is a generic nonspecific fault.

There is no LED for thermal regulator.

I posted the video link to indicate that the HLS and AGS errors were probably due to an actual overheat condition rather than faulty sensors.

If only one sensor was going off, then that might be a bad sensor.

With both suddenly going off, that points to an actual problem.

The sensors might be bad and you can test them in hot water to see where they trip.

If they do not trip (Open) at the indicated temperature, then they are faulty.

The High Limit Switch prevents the Heat Exchanger outlet temperature from exceeding 135°F (±8°F).

1730821861678.png
 

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