MasterTemp 400 won't stop heating at desired temp

  • Last Post 25 November 2020
cbwell posted this 24 November 2020

My MasterTemp 400 won't stop heating at the temp I've set.  This is true for both heating the pool and the spa.  I set the desired temp on the control panel as well as on the unit itself.  But, it just keeps heating, going past the set temp.  For instance, the pool was set to 85 and this morning it was 93 and still running. 

The control panel on the unit is currently only reading a '1' but the master control panel is reading temps accurately.   Even before the display panel was reading a '1' it was doing the same thing.

Any ideas?  It has a new control display membrane.

InyoRob posted this 25 November 2020

We spoke to a Pentair technical representative and he believes it is a bad control board. The control board is part number 42002-0007S. Click Here to View More Details on the Control Board