56
17. Service LED ON: “b3” Code
“b3” Code stands for “Gas valve sensed as “OFF” error. If gas valve is unpowered but flame is sensed, the
blower will run for 5 seconds then start a new ignition sequence. If error occurs 10 times during a call for heat,
the ICB will go into lockout.
Call for heat and test gas valve
Power cycle heater
OFF
ON
Step 17BStep 17A
b 3
Power cycle heater, in an attempt to clear the “b3”
code. IF power cycling clears to the “b3” message
and the heater fires, drop the temperature to
suspend heating. IF “b3” reappears, go to step 17B.
With heater in standby mode, test for 24VAC on
the gas valve (black & white wires), IF 24VAC is
present, replace gas valve (pg. 25). Otherwise,
replace the ICB (pg. 25).
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