System Description

WARNING: This page is about a different car, the 2004 Infiniti M45. However, it is still accessible from the selected car via links, so may be relevant.

The rear window defogger system is controlled by the BCM (Body Control Module), The rear window defogger is operated only for approximately 15 minutes. Power is supplied at all times

through 20A fuse [No.10, located in the fuse block (J/B)],
to the rear window defogger and door mirror defogger relay terminal 6,
through 20A fuse [No.11, located in the fuse block (J/B)],
to the rear window defogger and door mirror defogger relay terminal 3,
through 10A fuse [No.3, located in the fuse block (J/B)],
to BCM terminal 105.

With the ignition switch in the ACC or ON position, Power is supplied

through 10A fuse [No.4, located in the fuse block (J/B)]
to the door mirror defogger relay terminal 5.

With the ignition switch in the ON or START position, Power is supplied

through 10A fuse [No.1, located in the fuse block (J/B)],
to BCM terminal 68, and
to the rear window defogger and door mirror defogger relay terminal 1.

When the rear defogger switch in the multifunction switch is ON, Ground is supplied

to multifunction switch (rear window defogger switch) terminal 5,
through BCM terminal 10,
through BCM terminal 56,
through body grounds M24 and M114.

Then BCM recognizes that rear window defogger switch is turned to ON, Ground is supplied

to the rear window defogger and door mirror defogger relay terminal 2,
through BCM terminal 144,
through BCM terminal 56,
through body grounds M24 and M114.

With power and ground supplied rear window defogger and door mirror defogger relay is energized. When rear window defogger and door mirror defogger relay is turned ON.

Power is supplied

through rear window defogger and door mirror defogger relay terminal 5 and 7,
through condenser terminal 1,
to rear window defogger terminal 2.

Ground is supplied

to rear window defogger terminal 1,
through body ground B422.

This power and ground supplied rear window defogger filaments heat and defog the rear window. When rear window defogger and door mirror defogger relay is turned ON, power is supplied.

through rear window defogger and door mirror defogger relay terminal 5 and 7,
to door mirror defogger relay terminal 2.

Ground is supplied

to Door mirror defogger relay terminal 1,
through body ground B17 and B57.

When door mirror defogger relay is energized.

When door mirror defogger relay is turned ON, power is supplied

through door mirror defogger relay terminal 3,
to door mirror defogger terminal (Driver side and Passenger side) 6.

Ground is supplied

to door mirror defogger (Driver side and Passenger side) terminal 5
through body grounds M24 and M114.

With power and grounds supplied, door mirror defogger filaments heat and defog the mirror.

When rear window defogger and door mirror defogger relay is turned ON, power is supplied

through rear window defogger and door mirror defogger relay terminal 5 and 7,
to multifunction switch (rear window defogger switch) terminal 6.

Ground is supplied

to multifunction switch (rear window defogger switch) terminal 2,
through body ground M24 and M114.

Then rear window defogger switch indicator is illuminated.