Front window defroster note working

Hello Katherine, If your car has a cabin filter, I would check to see if it needs to be replaced.

Depending on the vehicle, it could be a vent door actuator

front or rear defrost?
what windows, there are many, front windshield?????
front:
dont use RECIRC mode. use fresh air, only
and make sure the dampers are in fact sending hot air to the windshield. if the dampers are not working it needs service
or a simpled blown fuses in the fuse box.
also, the car can have water engress. are the any damp spots
on the carperts. anywhere.?
are you using the A/C defrost mode, does it work.
do you know how to tell, its easy, check A/C mode.
A/c is also a dehydration system for the whole cab, it even ejects
water to the ground as you drive.

it is your blend door motor

The default configuration when all vacuum fails is to defrost vents. Most likely your vacuum supply to the switch is weak. Check the connection of the supply line to the intake manifold for damage. If no problem there, trace it to the switch on the control panel. If there is an accumulator, make sure it isn't leaking and is storing vacuum. If all this is good, look at any other vacuum lines connected to the intake manifold that may be leaking and possibly reducing the vacuum supply to the HVAC control line. Let me know if you have more questions.

Well it would be the "mode door GM pt#88986538" or the "mode control cam actuator GM pt#89023358" on the side of the heater case. The door would control where the air comes out and the actuator tells the door where the setting is at on the control head.

Try replacing the cabin air filter.

I had the same issue and then I got into a slight accident with a curb. When the collision place was fixing the car, I told them about the defroster and floor and they told me that they had to clean out a whole bunch of leaves and then airflow was restored. Have it cleaned, you may be surprised.

This is normal....everything is working fine...if the window is being defrosted.

The defrost on a car works by using the A/C to remove the moisture from the air (thereby lowering the relative humidity)
It also lubricates the seal within the A/C unit during the winter...reducing the chance of seizure/failure during the following summer due to lack of lubrication.

it needs service,
i guess front glass defrost fails.
and 2 things must work , AC and the defrost damper
or #3 (overloads the function)
my heater core bad and leaking.(or its 2 hoses)