Pentair Mastertemp not igniting


Well-known member
Mar 28, 2013
Central PA
So I had an issue where I put 240v to my (as hooked up) 120v heater. Well after replacing a handful of things, I got the heater back up and running however I did notice a long buzzing noise when igniting. I had the heater running a few times late spring and then not running for the past few months. Now here is what is happening:

1) turn on heater
2) I hear the blower start and run for about 10 seconds (assuming its waiting for the sensor to say its running)
3) buzzing noise from inside the unit that goes for about 5 seconds (assuming this is the igniter)
4) when it does flame, the blower stays on and the cycle repeats in about 30 seconds or so

So my first question is, when your igniter goes bad, does it make a sound or just silence? I hear buzzing coming from where the igniter is located. Is there a natural gas valve that could not be opening and that valve needs to be replaced? I'm looking to get parts ordered today so I can get this Dang thing up and running. Thanks


TFP Guide
Jun 4, 2012
western NY
You most likely have a spark ignition system. This system also utilizes the igniter as the flame sense circuit. Pull the igniter from the unit and use steel wool to clean it. Reinstall it making sure the mounting area is corrosion free...flame sensors need a good ground.

The delay at startup is the pressure switch proving timer to make sure the exhaust is clear and flowing. If it is lighting and going out, this is the flame sensor circuit. The system allows for the unit to "run Free" for a few seconds to allow for the flame sense circuit to establish a current flow. The flame sense circuit then takes over and controls the gas valve. If the sensor is dirty (they do need periodic service) then the circuit can not establish good current flow and it tells the gas valve to close since it does not think the flame is lit.