Water Temp Sensor

[jsoto58]

How do you check to see if the water temp sensor is working that does to a Pentair Panel?

My MasterTemp 400 shows erratic temperatures on the board. It is controlled by my Pentair Panel. It goes through the startup of 128 r13 but never starts. It initially shows a temp of 78 and then jumps to 120 something and stays there.
I checked the Thermistor and it shows 9.5 ohms. I had a spare one that I installed and still the same results.
It was working fine a couple of days ago, but now no go.

Any ideas?

 

[ajw22]

9.5 ohms is not correct. 9,500 ohms maybe correct. The thermistor should read 10,000 ohms at 76F.

Temperature Sensors - Further Reading

www.troublefreepool.com

Check the thermal regulator and bypass valve in the Mastertemp heater.

Pentair MasterTemp Heaters - Further Reading

www.troublefreepool.com

 

[jsoto58]

You are correct, it is 9.5k ohms.

Heater never starts its sequence, but led shows temp bouncing around. Temp at ET shows correct water temp.

 

[JamesW]

Show the whole system.

 

[jsoto58]

I placed a 10k ohm resistor on the thermister. The heater went through the initialization (128, R13) and then briefly showed 76 then jumped to 99 and then back to 76/77 and back to 99 and stayed there. The heater never tried to start. ET shows correct water temp and the setpoint was greater than water temp. No error codes present.
Heater was working fine last week.

Is this a board problem?

 

[JamesW]

I placed a 10k ohm resistor on the thermistor.

Show what you did.

 

[jsoto58]

I have already disassembled the resistor. I used alligator clips to connect to the leads of the thermistor wiring as shown in other posts. I did this correctly.

 

[JamesW]

Probably a bad board.

Did you check the wires carefully?

 

[jsoto58]

I will check the wiring thoroughly

If I need a control board, should I upgrade to the new 6 button? I have the old 5 button screen.
Do you have a part number?