i have a 94 teg, and my defroster takes upwards of 15 min just to clear the windshield. whats the problem here?

 

Have you tried...
engage the 'recirculate" button,
press the Air Conditioner to on,
put the heat to max,
press defrost.

With the air conditioner on, the "air is dried out"... with the recirculate on the "dried air" is reused.

You might try an electric "dip stick heater" to keep you engine temp up, overnight.