I have 2003-vintage H400IDL2 Low NOx heater. Pool controls are Aqualink RS6.
A few years ago the temperature sensor circuit on the RS6 board failed, so I have been manually turning the heater on/off since. (Previously the heater was in BO mode for remote operation.) I just upgraded the RS6 to iAqualink with the IQ900RS kit (rev R firmware). Pool temp via the RS6 is reading correctly now.
I cannot seem to switch the H400 back to BO mode for remote operation. (I note the Standby light on the heater only illuminates when the pump is running, which is believe is the correct behavior.)
With the filter pump running, and the H400 in Standby, I hold the DOWN arrow button and the MODE button simultaneously (for at least 10 seconds) but the display just stays blank. From what I've read, it should switch to BO. If I just press mode I can cycle between Pool and Spa with the temp displayed, and I can set the temp up and down without any issue.
Any ideas? The heater functions perfectly otherwise. Note this is an early H400IDL2 with the white circuit board that is integrated with the display module.