Mastertemp throwing E01 code

doncaruana

LifeTime Supporter
Aug 25, 2011
405
Northville, Mi
Heater has been working okay, last night we had a major storm. No electrical damage noted anywhere and we never lost power. However...

Today I noticed the heater had thrown an E01 code. The control board only has LED11 (Service Heater) and LED7 (Not sure what this is, it's right in the corner).

I had varying degrees of getting it to come on. It would come on and fire for a second then throw the code, then it would just throw the code almost immediately and wouldn't even try to fire.

Then I let it sit for a bit after opening everything to look at the ICM and lo and behold, it came on and started running. For maybe 15 minutes, then it threw the code again.

There is some old stuff from rodents in there, but just some shells. Nothing major noticed.

What are my likely culprits?
Thermistor (replaced in 2017, but it had different symptoms, just read a really high temperature IIRC)?
Thermal regulator?
Control Board?

Thanks in advance!
 

JamesW

TFP Expert
Mar 2, 2011
19,755
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.

Looks like a bad thermistor. I would replace it. If the problem continues, it's probably a bad circuit board.

Check the wiring to make sure that it's not damaged.

You can check the resistance of the thermistor and compare it to a standard 10k thermistor chart.

 

doncaruana

LifeTime Supporter
Aug 25, 2011
405
Northville, Mi
I pulled the wires and put my meter on the thermistor and it came back at 9k (pool is about 80 degrees right now). Pentair said the good reading on the thermistor (that reading matched the temp) meant it was the control board. Also, for the few minutes it was running, the control pad read the right temp on it as well.

Obviously I trust you more than them, but since I just hung up with them, I wanted to pass it along...

PS - since this is a saltwater pool, probably wouldn't kill me to replace the thermistor again anyway, it's just a matter of finding one right now...
 
Last edited:

JamesW

TFP Expert
Mar 2, 2011
19,755
9k ohms is about 81 degrees. So, that looks ok.

However, it might be an intermittent problem.

I would verify that the wiring is good and replace the thermistor before buying a circuit board.

At least pull out the thermistor and check to see if it looks good.

Check the resistance of the thermistor at different temperatures to see if it matches at colder and warmer temperatures.

Get a glass of warm water and cold water with a thermometer and dip the sensor in the water to see if it matches the thermometer.

If it matches at 3 different temperatures, it's probably a bad circuit board.

Since you have evidence of mice, double check the wires because mice like to chew on the wires.


 

doncaruana

LifeTime Supporter
Aug 25, 2011
405
Northville, Mi
I actually was thinking of taking a 10k resistor and putting the leads for the thermistor. That should make the heater think it's about 77 degrees. If it still gets an open and there aren't any wiring issues, then it has to be the control board. Is that a valid test?
 

doncaruana

LifeTime Supporter
Aug 25, 2011
405
Northville, Mi
So I'm seating here next to the heater as it's running with the 10k resistor. When it first fired up it read 77 degrees. But I've notice the reading is slowly going down. It was at 69 after 10-15 minutes when I started typing this. It's at 44 now. Seems like that is indicating that the reading for my fixed resistor is somehow increasing, ie slowly creeping toward an open circuit.

Now, if I'm interpreting all that correctly, I'm guessing I need a new control board. Does that make sense or am I off base?
 

JamesW

TFP Expert
Mar 2, 2011
19,755
Seems like it's probably a bad circuit board.

Check the resistor to see if it still measures as 10k.

If yes, you probably need a new circuit board.
 

doncaruana

LifeTime Supporter
Aug 25, 2011
405
Northville, Mi
The wires looked good on visual inspection. No sign of deterioration or rodent chewing. The heater is 9 years old.

Heater still running...and holding at 41 degrees on the display... Kinda bizarre at this point...
 

JamesW

TFP Expert
Mar 2, 2011
19,755
Definitely odd. Check the resistance of the resistor. If it's still 10k ohms, I would say that the circuit board is bad.
 

doncaruana

LifeTime Supporter
Aug 25, 2011
405
Northville, Mi
I checked it with the circuit still intact and got 4.3k. But when I disconnected the resistor and just checked it, it was still 10k. Interestingly, I checked the leads going back to the circuit board at that point and got 7.5k.

Should get a new board here Monday.
 
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