11
Servicing should only be performed by a Qualified Service Agent
Combustion blower
The Combustion Blower is an assembly that includes the blower housing, blower motor and an electronic
speed control. The Combustion Blower is controlled by the CCB (Central Control Board), see Control System
Hardware on page 37.
The CCB sends 120 VAC from the J2 socket on the CCB circuit board to a 3 pin wiring socket on the blower
assembly, see CCB Circuit Board Layout on page 41 and Figure 7 below. The CCB also sends a PWM (Pulse
Width Modulation) signal from the J13 socket to a 5 pin wiring socket on the assembly. The PWM signal is
an electronic instruction to start, stop and control blower speed.
The Combustion Blower runs at higher speeds during the Pre/Post Purge operating states and runs at a
lower speed during the Igniter Warm up operating state, see Table 6 on page 48 for a list of operating states.
The Igniter Status icon is displayed on the Control System LCd during the Igniter Warm up operating state,
see Table 5 on page 47.
service note:
The 5 pin PWM signal plug MuST remain plugged in to the 5 pin socket on the blower assembly at all times.
disconnecting this plug will cause the Combustion Blower to run at maximum speed continuously. This may
cause rough starts, rough operation and/or the
Ignition Failure
fault condition and Control System lock out.
If the electronic speed control is functioning properly Combustion Blower speed should noticeably reduce
during the Igniter Warm up operating state. If blower speed reduction does not occur during the Igniter Warm
up operating state ensure the 5 pin plug from the CCB is securely plugged into the matching 5 pin socket on
the blower assembly and that the J13 plug is securely plugged into the J13 socket on the CCB circuit board.
Perform a close visual inspection of the pins inside the plugs and sockets at the Combustion Blower and the
CCB, replace any worn or damaged wiring harnesses as necessary.
BLOWER MOTOR
AND ELECTRONIC
SPEED CONTROL
COMBUSTION BLOWER ASSEMBLY
BLOWER
HOUSING
3 PIN
WIRING
SOCKET
5 PIN
WIRING
SOCKET
Figure 7
