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Aqua balance weil mclain a03 error

Any help would be great. We have an a03 error that co.es and goes . Replaced board  and mixing valve already.  Spoke with tech support and everything checks out while on site. Any ideas? 


  • Tim_D
    Tim_D Member Posts: 129
    A03 is a high limit lock out. This is almost always a water flow issue.
  • Slacker
    Slacker Member Posts: 1
    Check your plate heat exchanger it has buildup in it . If you have hard water in your area and don't have a water softener install ed your plate heat exchanger is blocked. Don't need to replace it. Remove it from the unit look into openings with light it will have scale buildup. You could flush that out by filling with water and shake out the scale on the same side you see it in. I have to deal with 112 of these units for the last six years learned a lot that's not in manual.