Bosch BGH96 - Error Flash Code Diagnostics; No Flash and No Fan (System Start Failure)

Troubleshooting Guide Bosch 96% AFUE Gas Furnace | 7
BTC 770502101 A | 01.2019
Data subject to change
3 Error Flash Codes
3.1 No Flash and No Fan (System Does Not Start Normally)
Troubleshooting Chart
Start
Are there any
loose wires or wrong
connections?
Correct
wiring
according to
wiring diagram
Yes
No
Is there
power to the unit?
See Figure 1
No
Is the door
switch working properly?
See Figure 2
No
Replace the
door switch
Is the
transformer
working properly?
See Figure 3
Is the blower
access door closed
or fixed properly?
No
Ensure the
blower access
door is closed
properly
Yes
Yes
Check the
incoming power
supply at
connection box
No
Is the
PCB Board
sending 18-31V signals?
See Figure 4
No
Replace the
transformer
Is there
a blown fuse?
No
Replace the
control
board
Replace
the fuse
Yes,
Heating
Yes,
Fan Only
Istherea
callforheat?
See Figure 5
Istherea
callforfan?
See Figure 6
Check the
thermostat
settings and/or
replace the
thermostat
No No
Replace
the control
board
Yes
Is there
power to the
circulating fan motor?
See Figure 7
Yes
Replace
the circulating
fan motor
No
Leave “Park” terminal unused.
Yes Yes
Yes
Yes