Master Temp 400 not heating to set temp

Paso Jack

New member
Mar 14, 2021
Paso Robles, CA
Hi. My heater is not heating to the set temp. The heater is reading 104 but the control panel is reading 99... it will not heat past that. The water temp is 95. I have replaced the thermal regulator and the thermal sensor. Any help would be appreciated.


Gold Supporter
TFP Guide
Jul 21, 2013
Northern NJ
Pool Size
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
Welcome to TFP.

What model control panel and automation of you have?

When the heater hits 104 it will shut itself off. That is the maximum temperature the heater will go to.

You say you replaced the temperature sensor. Did you use genuine Pentair part Thermistor p/n 42001-0053S?

Has there been any repairs to the wiring in the MasterTemp? Problems with critters chewing on the wires?

Have you checked the temperature sensor using a multimeter and a bowl of hot water and see that it reads correctly? Temperature Sensors - Further Reading

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