Heater blowing cold air. Any suggestions?

 

Clogged heater core? Is the coolant up to full temp before the heat is on?

Do a coolant flush and use g12 to replace the coolant.

 

With the car warmed up, put the control on econ, push each vent, low, middle, upper. See if you get any heat from of them. You are trying to see if your heater core is getting hot. Turn fan to lowest setting, Put on recirculate and see if you can hear the baffle move. If you get heat that way there may be a problem with a baffle.
Pull off the windshield cowling, remove the rubber piece, slide the cowling off. You should see your cabin air filter there, good time to replace if dirty. When getting a replacement measure the existing one and buy the exact same size, there are two sizes. Online stores and parts stores will get it wrong every time as there is a vin split and the wagon all produced in 98.
Looking in the filter area you should see a baffle. Have a friend adjust the controls to recirculate and change temps to see if that moves.
Also could be the blower control module. See pictures on my album. You can check it yourself for burn marks. Sorry not more specific, but at least you can check a few things.
And if hooked to a vag com there may be an error code.