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
This is a dirty throttle body. Very common on our trucks.
I believe when you turn on the rear window defroster the heated mirrors also turn on
Try pulling the steering wheel one way, or the other while turning the key.
with a push button directly under the defroster control
check your gas filter
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.
Its on a spring loaded tensioner. Usually a wrench or socket extension(square) will be able to let you turn the tensioner to release the tension on the belt
Those all have electronic transfer cases. You put the vehicle in neutral or park, and turn the knob to either 4H or 4L. The hubs lock automatically.
In most cases controlled by rear window defogger switch
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.