Check the vacuum supply from the engine. If it is disconnected or cracked the system will default to defrost only.
The defrost function simply directs air over the inside of you windshield. It's temperature is controlled by the temperature dial on your environmental controls.
The fastest way to defrost a windshield is to turn the defrost vent on without heat or simply open the windows. Another option is to warm the inside of the car by turning the heater on.
It only stays on when the air flow is turned to defrost. It does this because the air condition has a dryer on it that dries the air which defrosts the windshield better.
no heat to front window went defrost is on
on the dash below the windshield.
yes, however, if the ac does not work then you will be unable to blow cold air on a hot steamy windshield to defog it.
does fan door motorized or on a vaccuum line when you switch from AC to defrost?
It have battery
You can't defrost then refreeze anything :)
You most likely have a bad vacuum hose in the engine compartment or a bad control switch.
Yes, the ac will run in the defrost position to dry the windshield.
Start driving with your air conditioning on defrost, the AC will defog the windshield but you need to be moving.