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Installation Instructions
Symptoms of
Fault
Abnormal
Fault Description(s)
Code
Operation
— Lockout due to
failed ignition
E7
Furnace fails
— Lockout due to
to operate
E8
too many flame
dropouts
— Incorrect line
Furnace fails
PR
to operate
voltage polarity
Furnace fails
— Control failure
BE
to operate
Abnormal
— Abnormal T-stat
Thermostat
nL
signals
Signals
Abnormal
— Low flame sense
furnace
FL
current
operation
Table 28
Troubleshooting Chart
Display
--
H1
H2
Operation
C1
Codes
C2
CF
dF
Table 29
Unit Operation Codes
5 4 |
Possible Reason
— 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
— Wrong L1/L2 connection
— Control module failure
— Thermostat wiring issue
— Thermostat failure
— 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.
Online Help Resources
Alternatively, please visit our Service & Support webpage to find FAQs, videos,
Meaning
service bulletins, and more;
Standby mode
cellphone to scan the code below.
1st stage heating
2nd stage heating
1st stage cooling
2nd stage cooling
Fan only mode
Defrost mode
Figure 47
Bosch 96% AFUE Condensing Gas Furnace - BTC 770503101 J (06.2023)
Corrective Action
1. Turn the gas valve switch to "On"
2. Replace ignitor
3. Remove the blockage
4. Clean with steel wool.or replace the
flame 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.
1. Correct the wire connection
1. Replace control module
1. Correct the wire connection
2. Replace thermostat
1. Clean/sand flame sensor with steel
wool.
2. Inspect for proper sensor alignment.
3. Compare current gas pressure to
rating plate info. Adjust as needed.
www.boschheatingcooling.com/service
Cautions And Notes
— Turn power OFF prior to repair.
— Turn power OFF prior to repair.
— Turn power OFF prior to repair.
―
— 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.
or use your
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