mastertemp 400

  1. M

    MasterTemp 400 HD Shutting Off Rapidly

    I have a mastertemp 400 HD heater and I'm having an issue with maintaining the temp. Initially when you turn it on, it stays on and heats it up well. However once it reaches the set temp, it will shut off Rapidly instead of staying on for a few minutes to heat it back up to a degree or two over...
  2. generessler

    Mastertemp 400 control board dead?

    Hi. Bought our house this past July. The heater - Mastertemp 400 - worked fine. We used it at least once per month through November. At one point - I think in August - Error 01 (Thermistor) was a problem. I replaced that, but later found the real problem was the connector on the control board...
  3. B

    MasterTemp 400 won't turn off

    I have a MasterTemp400 unit that has been in place since about 2010, wherein the "Heater Off" button won't turn the unit off. The button (and all other buttons) feel incredibly tactile and seem to be functioning. However the Heater Off button doesnt turn off the LCD display like it does in this...
  4. P

    Pentair MasterTemp 400 keeps cycling on & off

    I have a MasterTemp 400 that I have been troubleshooting since last year. I've check different foruns and looks like a common issue, but I have yet to see a resolution. Perhaps you can help. As soon as I turn the heat on, I see a 75 reading. It 'heat' blinks to call for heat and then steady...
  5. D

    Just opened pool but heater won't start

    Hi, My Pentair Mastertemp 400 goes through its electronic startup routine and then reports a HLS error (and service heater led). My water is circulating normally, my chlorine generator is saying that it is working but the heater stops as quickly as it starts without lighting or blowing. I...
  6. JoyfulNoise

    MasterTemp 400 Failure To Ignite Issue - SOLVED

    I wanted to document this on the forum threads since this issue got diagnosed and solved via PM. First, let me give total credit to our esteemed forum expert @JamesW for helping me to diagnose, test and fix this heater issue. James' help saved me from calling in a "pool service" guy and...
  7. Kihon

    Another.....Mastertemp 400 with AGS LED + Service Heater LED

    Hello TFP experts. I have Mastertemp 400 that's about 5 years old. I have attempted a a deep dive search here and found a few threads that very similar. MasterTemp 400 Heater won't stay running, but it was never confirmed if a new control board solved the problem? Mastertemp 400 - Burner...
  8. 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...