Rear Window Defogger System does not Operate: Description

The rear defogger & mirror heater switch on the multi-display inputs a request signal to the A/C amplifier (ECU). Then, the A/C amplifier turns ON the RR-DEF relay built into the power distributor in response to the input, thus switching ON the rear defogger. (The deicer and mirror heater also turn ON at the same time)
HINT:

The power distributor is built into the J/B No.2.
The RR-DEF relay is built into the J/B No.2. For inspection, use the terminals in the J/B No.2.
If RR-DEF relay is malfunctioning, replace the J/B No.2.