One problem related to defogger has been reported for the 1996 Volvo 850. The most recently reported issues are listed below.
I own two vovo 850s. One is a 1993 Volvo 850 glt and the other is a 1996 Volvo 850 turbo wagon. The air conditioner in both cars developed leaks in the evaporators. The 1996 car developed the leak in 2003. I had it replaced in 2004 for $1400. The 1993 Volvo a/c evaporator also developed a leak. To replace it will cost another $1400 plus. Volvo denies that there is any problem with the design of the a/c evaporators. I suggest that the fact that in my two cars both evaporators have developed leaks indicates that there is a defect. Note that living in virginia the a/c is used seasonally. I would be curious to know how many evaporators Volvo replaces per year in what models and what year made. My guess is that there is a pattern here that Volvo is aware of (must be) and refuses to acknowledge due to potential cost to the company.