I am having problems with my nav over the last few weeks. When I pop the nav up, sometimes the screen comes on, and sometimes it doesn't. This is different from the normal cold weather dimness issue. I have an aftermarket stereo, so I can't rely on voice feedback to determine if the nav is working and the screen is not, or if the whole unit isn't working.

What are your thoughts on troubleshooting this? I am getting ready to sell this lovely, amazing car, and I don't want the next owner to have problems with this.