Your problem could be one or more of many. I suggest you go to the aqua hot hydro hot website with your Hydro hot model Number and download the "Service Manual" (Not Owners Manual). The service manuals have a wealth of info in them and fixes. To check out the controller voltages and all else. There is also some recent posts by Gerald on things he just did to get his running properly. But I found the Service Manuals a great help. They don't have one for all but another number may be the same as yours. I could not find one for my 500 Model but the 200 covered mine too.
