Whats wrong with my Optiarc 7173

I purchased on Optiarc 7173 a few days ago. It works OK when reading DVD+r and when writing DVD-r or DVD+r. however it simply wont read DVD-r.What do you think this could be.

How do you know it writes -R ok if you can’t read them? If they check ok on another drive, I say, replace the 7173.

Before recommending to replace the drive, I would first check other media. Maybe the DVD-R you have are crap. What mediacode does DVD Identifier show for these discs?