Aqua Hot 450 DE1 Operates NORMALLY but NO STATUS LIGHTS on AH Control Board

[Ron Shantos]

Turned on diesel on the AH DIESEL SW on control panel.  Could hear a relay/or contactor on the control board "CLICKED" but NO display or control lights at all on the control board.  HOWEVER, AH fires, heats coolant, and produces heat in BOTH ZONES (both zone pumps work normally).  As a sanity check felt the exhaust pipe and it was HOT.  Unit appears to be totally functional yet NO STATUS LIGHTS on the CONTROL BOARD. 

ALSO, checked the FRB for a fuse and could  NOT find any fuse or reference to the AH.

Thoughts or suggestions. 

[Tom Cherry]

3 hours ago, Ron Shantos said:

Turned on diesel on the AH DIESEL SW on control panel.  Could hear a relay/or contactor on the control board "CLICKED" but NO display or control lights at all on the control board.  HOWEVER, AH fires, heats coolant, and produces heat in BOTH ZONES (both zone pumps work normally).  As a sanity check felt the exhaust pipe and it was HOT.  Unit appears to be totally functional yet NO STATUS LIGHTS on the CONTROL BOARD. 

ALSO, checked the FRB for a fuse and could  NOT find any fuse or reference to the AH.

Thoughts or suggestions. 

Use a needle or a pin.  Check for voltage going to the LED/NEON contacts that power the status lights.  Are ALL the lights out?  If so, somewhere you lost the common ground. Start with the burner…its working.  If there is voltage…measure to a nearby ground. An AC round ground pin in any AC outlet is the same as the DC grround.  Then switch to electric heat. No status light….voltage to good ground. No sense in worrying about switches and indicator lights before you troubleshoot….

[TomV48]

2 hours ago, Tom Cherry said:

Use a needle or a pin.  Check for voltage going to the LED/NEON contacts that power the status lights.  Are ALL the lights out?  If so, somewhere you lost the common ground. Start with the burner…its working.  If there is voltage…measure to a nearby ground. An AC round ground pin in any AC outlet is the same as the DC grround.  Then switch to electric heat. No status light….voltage to good ground. No sense in worrying about switches and indicator lights before you troubleshoot….

I lost one of my two, four light old school tank monitors. Looked and looked.  Tested and probed.  Turned out the digital display plug in strip was ever so slightly dislodged.the eye missed it, but loosened and pressed back tight and bingo lights.  Turns out even low current low voltage electrical connectors can suffer open circuit loose connection tiny corrosion and lose conductivity.