Pentair Mastertemp 250 not starting

[cdchris1]

I am having issues with my Pentair Mastertemp 250. When I opened, it started up and ran just fine for a couple of days and then I shut it down. Air temps have been a little cold for swimming until recently, so I did not have it running until today. I noticed that it was not on and saw a 'Service Heater' led on. So I started trouble shooting on my lunch break. Nothing happens when the heater starts. The panel calls for heat, the control enters startup, then there is a click and the 'Service Heater' led comes on. On the back of the control board, I get an AFS light. I tried jumping out the air flow switch. It does the same thing upon startup, but I get a HLS light with the switch jumped out. It goes back to AFS when I pull the jumper. There is no light on the ignition control. That is all the farther I got before I had to get back to work. Just wondering if anyone has any ideas on what to look for next. I plan on pulling the cover for the blower motor and checking the voltages there and the cap later. Thanks for any tips.

 

[ajw22]

The blower fan is the first thing that should start up.

Check the Air Flow Switch with a multimeter and confirm it is open before the blower fan starts.

Read Pentair MasterTemp Heaters - Further Reading

 

[cdchris1]

The air flow switch was open. I could not focus on work, so I ran out and went through the troubleshooting from the manual. I was not getting voltage to the blower, so I went back to the ignition control module per their proceedure. When I jumped F1 and F2 together, the blower started up indicating a bad ignition control module. Is there anything else I should test, or is everything pointing to the module like the manual says? Thanks again.

 

[ajw22]

Check that no rodents got into the heater and chewed any wires.

If all wiring is intact then replace the Fenwal box.

 

[cdchris1]

All the wiring looks good, and no signs of any critters. I'll get a new box on order. Thanks for the help!