Below is a list of all Diagnostic Codes for the UHS Heater. Troubleshooting Steps for
each Code are covered on the following pages.
Diagnostic
Code
Description
AC Blower Vacuum Switch closed
AO Blower Vacuum Switch open
BD Bad board or secondary high voltage fault
CE Communication Error Between Control Module and Display Interface Assembly
EE Bad board
HF Flame present with Gas Valve not energized.
HS
Maximum return water temperature exceeded and / or rapid water temperature rise.
IF Ignition Failure
IO Ignitor Circuit Open
LO Water Pressure Switch, Vent Pressure Switch, or Temperature Limit Switch Fault
PF Voltage polarity reversed, low voltage detected
SB Keypad failure
SF Temperature Sensor (thermistor) input failure
19
Diagnostic Codes
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