I had the same problem with my 2000 Bug and it turned out to be battery issue. Because my car has been sitting in the parking lot for the winter battery was so weak that blower didn't work. And as soon as I replaced the battery it was working. That might help.
the floor pan could be sagging due to rot around the heater channel. common cause.
coolant level could be low not letting it circulate through the heater core, causing it to blow cold. Also, if the coolant level is low it will in turn overheat.
Could be a bad thermostat or heater core
Could be a Faulty relay.
it could be a couple of things you could have a bad thermostat or a bad heater core
Your heater coil is bad.
there is a short somewhere in dash or heater, you need to fix that to stop fuses blowing
If the fan is not blowing, a fuse may be the cause. If there is just not warm air being blown by the fan, check your coolant level in your radiator. Low level of water and coolant will cause the heater to blow cooler air.
well you could just turn the heater off heater blower ---- If it is a car heater then check your coolant level. the heater is driven off a heat converter that is fed by the radiator system. When the coolant fails to pump round the radiator system the car internal heater doesn't work. Driving without coolant in the system will result in the engine overheating and seizing.
It could be a thermocoupler, happened to my furnace in middle of night a few years ago.
the heater box is under the dashboard most of the time in the middle. The heater blowing system have doors . The door for the foot is next to your leg he have one metal cable could be this come out. If yes, have to clip it back. This electric its more difficult but just check first
If it's blowing and you can tell the compressor is still kicking on when you turn the A/C on, the Coolant probably just needs to be recharged. Especially in a 9 year old car.