gas heater

  1. 1

    Mastertemp400 cycling in spa mode

    Hey experts, When I turn my mastertemp 400 onto spa mode. It will run for about a minute then turn on a HLS error light. After maybe two minutes light will go off and it will go through the same process again. This issue first started with an E05 error message. I came to this forum to start...
  2. M

    Master temp 400

    Turn the heater on fan turns on then immediately goes to service mode. Water flow is good, gas pressure good, changed board, changed air flow switch still goes to service light immediately. Any ideas.