Volkswagen Eurovan vent diverter door stuck shut

SOURCE: When turned to defrost, no

The vent flap foam lining has come loose and needs to be removed or reglued . A spray on contact adhesive works best , don't glue the flap to the vent casing.

SOURCE: 1986 VW Golf heater blows cold air

The heater in your car depends upon a flow of hot coolant going through the heater core in order to get hot air into the car. If the heater core is partially plugged, it will restrict the flow. If you have a head gasket that is putting exhaust into the cooling system, it will eventually get into the heater core. When this happens there is no coolant in the heater core to make the air warm. If the water pump vanes have corroded away the result will be very poor coolant circulation causing the heater to not blow hot air. If your car is equipped with a heater control valve that is not functioning properly, the coolant flow will be restricted. One or a combination of these factors is likely the culprit in your case.
if the car is not overheating, the thermostat is working fine.... replace or flush the heater core multiple times to try and eliminate sediment build-up.

SOURCE: 1999 volkswagen beetle , a/c blow a little air on

Your a/c gas (134a) is too low, there is a safety feature for the a/c compressor to "kick off" if that gas (134a) is too low thus saving your a/c compressor from seizing up. Have a garage check to see how much is in the a/c system they can easily recharge the system for you. Keep in mind this is the simplest fix and most common problem from what you described.

SOURCE: How do I remove the

This should help. Just have your radio code before pulling it out or cutting battery power from the car, it will go to SAFE mode.

SOURCE: 2003 volkswagen eurovan light on dash is a circle

that is to notify you to have your brake linings(pads) checked and replaced. you have a sensor on one your pads and it triggers light when pads get low.
if helpful please rate 4 thumbs.