Bosch BGH96 - 7 & 8 Flashes (Ignition or Flame Dropout Lockout)

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Bosch 96% AFUE Gas Furnace Troubleshooting Guide
01.2019 | BTC 770502101 AData subject to change
3.2 7 Flashes (System Lock-Out due to Failed Ignition)
8 Flashes (System Lock-Out due to too Many Flame Dropouts)
Troubleshooting Chart
Start
Are there any
loose wires or wrong
connections?
Correct wiring
according to
wiring diagram
Yes
No
Does the
unit show 1 LED flash
after restart?
No
Is the
ignitor “glowing”
red/orange?
Replace the
PCB Board
Is the
ignitor working
properly? See
Figure 8
Is the flame
sensor dirty or
broken?
Clean with
steel wool or
replace the
flame sensor
Properly
ground the
wire
Is flame
reaching the flame
sensor? (visual
check)
Replace the
ignitor
Is there a flame?
(visual check)
No
Replace the
PCB
board
Is there a
signal to the gas valve?
See Figure 10
Is the wire
grounded properly?
See Figure 11
Replace the gas
valve if the
pressure cannot
be adjusted
Check
incoming gas
supply
quality
Does the
manifold gas pressure
meet the requirement?
See Table 1
Adjust the
inlet gas
pressure
Is there
power to the ignitor?
See Figure 9
Check the wire
connections
between
ignitor and
PCB Board
Yes
Yes
Yes
Yes
Yes
No
Replace the
PCB
board
No
Yes
Is the inlet gas
pressure meeting the
requirement? See
Table 2
Adjust gas valve
to ensure it
meets gas
pressure
requirement
Yes
No
Unit should
work
normally
Is gas valve
switched to
“On” position?
Yes
Yes
Turn the gas
valve switch
to “On”
No
The flame sense signal should be 1-6 microamps.
No No
Yes
No
No
Yes
No
No
Remove
the
blockage
Are orifices
blocked or clogged?
(check burner)
Yes
Yes
No