Installation, Operation & Maintenance Manual Bosch 96% AFUE Gas Furnace | 51
Bosch Thermotechnology Corp. | 04.2019
Data subject to change
Symptoms of
Abnormal
Operation
Associated
LED
Fault Description(s) Possible Reason Corrective Action Cautions And Notes
RED
Furnace fails
to operate
7 FLASH
8 FLASH
— Lockout due to
failed ignition
— Lockout due to
too many flame
dropouts
— The gas valve switched off
— Iginitor failure
— Orifices are blocked/clogged
— Flame sensor dirty or broken
— Furnace improperly grounded
— Manifold gas pressure does not
meet the requirement
— Inlet gas pressure does not meet
the requirement
1. Turn the gas valve switch to “On"
2. Replace ignitor
3. Remove the blockage
4. Clean with steel wool.or replace the
fl ame sensor.
5. Properly ground the wire
6. Adjust the gas valve. Replace the gas
valve.
7. Check incoming gas supply quality.
Adjust the inlet gas pressure to meet
requirement on nameplate.
— Turn power OFF prior to repair.
Furnace fails
to operate
9 FLASH
— Incorrect line
voltage polarity
— Wrong L1/L2 connection 1. Correct the wire connection — Turn power OFF prior to repair.
Furnace fails
to operate
10 FLASH
— Gas valve fault
code
— Valve receives voltage from a
short
— Control module failure
1. Correct the wire connection
2. Replace control module
— Turn power OFF prior to repair.
Furnace fails
to operate
SOLID — Control failure — Control module failure 1. Replace control module — Turn power OFF prior to repair.
AMBER
Normal
Operation
1 FLASH
— Call for heat
active
―――
Normal
Operation
4 FLASH
— Y thermostat
demand without
G
— G wire not connected properly
— Thermostat failure
1. Correct the wire connection
2. Replace thermostat
―
Abnormal
furnace
operation
RAPID
— Low flame sense
current
— Flame sensor is coated/oxidized
— Flame sensor is incorrectly
positioned in the burner flame.
— Lazy burner flame due to
improper gas pressure or
combustion air.
1. Clean/sand fl ame sensor with steel
wool.
2. Inspect for proper sensor alignment.
3. Compare current gas pressure to
rating plate info. Adjust as needed.
— Turn power OFF prior to repair.
— Clean flame sensor with steel
wool.
— See Section 8 for piping
details.
— See rating plate for proper gas
pressure.
GREEN
Abnormal
furnace
operation
RAPID
— Control in Factory
Test mode
— Control board error
— Control module failure
1. Restart furnace
2. Replace control module
— Turn power OFF prior to repair.
Normal
Operation
1 FLASH — Standby mode ― ― ―
Table 26 Troubleshooting Chart
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