Whenever I use the defroster on my '92 SE, I slide the temperature all the way to hot. The air blowing on the windshield is hot, but the vents blow really cold air. Is there something wrong with the system or is that what it's supposed to do?

 

As long as your vents blow hot air in the non defrost mode with the heat to maximum, you are ok.

On my 4th gen, on defrost, only the windshield gets air. Vents get nothing.

 

Mine does the same thing and I read somewhere that the cold air (specially during the winter/rainy season) is directed on purpose so the condensation can be removed quickly. It is similar to when you have condensation you turn the AC own and all the moisture is removed by AC. First time that happened to me I though something broke in the heating system.

MSK 90SE