Hey guys new to the forum and I’ve already done some research but looking for some help. I have a pentair master temp 400 pool heater. Recently I went thru and replaced the thermistor, HLS, AGS, SFS, and thermal regulator. Now the issue I’m having with the heater is that it turns on, I hear the blower turn on and then it Ignites, it runs for about 2-3min and then turns off and I get a AFS light and service light that comes on. If I turn power completely to the heater it does the same cycle over again. The pool heater was working fine and just started doing this. Any recommendations on where to start? Thanks
Mastertemp 400 heater AFS light
- Thread starter jorge.perez.rn
- Start date
- Jul 21, 2013
- 65,118
- Pool Size
- 35000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-60
Be sure the tubes to the AFS are connected on both ends and that there is no rodent damage.
Replaced the air flow switch with a new one and ensured the tubes were connected and no reoffend damage. Still getting same issues. The heater will run for about 5-10min then the AFS light and service light come on. If I turn the heater off and restart again, I hear blower start and after about 10 sec it ignites and runs but then will turn off again after about 5 min
The next time you try, have the case open and block a portion of the blower orifice with your hand and see if the problem still happens. Twice I have seen that blocking a few of the fan inlet vents stopped that problem. The first time it was totally by accident that I had my hand resting on the orifice. Heater stayed running until I removed it as I stood up and the got an AFS error. Second time was just a try and it worked. Blocked a few of the vents with Plast-Aid and they are still working. Took a couple of tries, you don't want to block too much or it won't work either.
Last edited:
This worked for me. I placed blue painters tape over some of the fan inlet vents and the heater stayed on. I know it worked and it worked for you as well. But trying to understand why this works . Thanks
Air Flow Switch works on low pressure (vacuum). Blocking a portion of the orifice increases that in the orifice body and actuates the switch.