Rear Window Defogger System does not Operate: Description

with Navigation System: 

When the rear window defogger switch, which is built into the multi-media module display assembly, is operated, the operation signals are transmitted to the A/C amplifier assembly through AVC-LAN and BEAN. When the A/C amplifier assembly receives the signals, it turns on the DEFOG relay to operate the rear window defogger. 

without Navigation System: 

When the rear window defogger switch, which is built into the integration control & panel, is operated, the operation signals are transmitted to the A/C amplifier assembly through AVC-LAN and BEAN. When the A/C amplifier assembly receives the signals, it turns on the DEFOG relay to operate the rear window defogger.