In most cases controlled by rear window defogger switch
I believe when you turn on the rear window defroster the heated mirrors also turn on
with a push button directly under the defroster control
Some vehicles automatically turn on the a/c when you turn on the defroster. A/C removes humidity from the air and allows the defroster to clear the windows faster.
The heater core is leaking coolant.
Many auto manufacturers engage the AC compressor when the defroster is used because the AC system also dries the air. In a humid environment the drying effect of the AC can help keep the windshield clear.
Turn the defroster on. If you have a separate AC switch, turn it on also. The AC should come on with the defroster automatically, but might not. If no AC, set the vent control to outside air instead of recirculate.
Turn off the defroster.
You have a leaking heater core. You might smell antifreeze if you turn on the defroster.
When you turn on your back window defroster, it activates a heating element that can create electrical interference. This interference may disrupt the radio signal, causing static or loss of reception. Additionally, the defroster draws significant power from the vehicle's electrical system, which can affect radio performance if the system is not designed to handle the load.
when you turn the defroster on, it also lets the air conditioner cycle to kind of like dry the air so to speak, and to keep the a/c compressor lubricated. This also can bog the motor sometimes whenit dosent run constantly
If you have the defroster on, the ac comes on automatically.
Yes, the windshield defroster will turn the A/C compressor on.