I am having issues with a Bosch aquastar 125HX and I am hoping that somebody has some experience with it! The guys athe the Bosch tech support line only seem to be able to direct me to service bulletins which do not quite fit the description of my trouble or fix it. The heater seems to perform flawlessly when the cover is off but is unreliable when the cover is on! This is driving me crazy since I think I have tested everything well. If anyone has some input it would be greatly appreciated! Basically the unit will light and relight immediately after the water has been shut with no problem when the cover is off. Put the cover back on and it will light but not always immediately relight. Once the unit fails too light you have to wait 5 to 10 min before it will light again. Suggestions anyone??
Drill some large holes in the cover so the unit can get the right air to gas mix.When you work it with the cover off it can breathe. With it it on it cannot get the correct air/gas mix to make the thing work properly. MY best guess. Another thing is this when you cover it and the heat gets excessive withint the unit and it does brother! it probably shuts down a high limit to keep from melting that cheap cover. My opinion.
chek the flame sencore it could be coroided take it out clean it with sand paper this sould resolve the issue
For ignition issues … try moving the BLACK chassis ground wire from the controller directly to the metal chassis, instead of it sitting on the top of the plastic control unit retention screw. Since I attached the BLACK chassis ground wire directly onto the metal chassis, the pilot ignition and timing has been greatly improved with direct contact to the chassis. I have spent endless hours trying to figure out how to make our Aquastar 125 HX tankless heater more reliable. Providing you don’t have any other component issues, this mod. may do the trick for you as well. : )
Good luck! 