Navigation DVD drive problems

[NoDef]

Since the weather has gotten hotter, I've been having trouble with my NAV DVD ('03 MKIV). Occasionally, the nav computer cannot read the map disk. I think this is related to the heat, but I'm not sure.

One other wrinkle, the drive no longer recognizes the original nav DVD due to what I'm guessing are scratches. (I have similar problems reading it on my computer) Luckily, I made a backup (as suggested in these forums) however the backup is having the read issues I mentioned above.

I've tried to a burn new disk using several different brands of DVD-R and DVD+R with little difference in performance. Similar tests with different writers also lead to sporadic behavior.

Is there a common failure mode for these units. Since I've tried so many different media types with similar response, I'm guessing it's a failing drive (maybe heat affecting the output of the laser diode). I'll probably try to borrow an original pressed disk to rule out the media issue.

In the mean time, can anyone make any suggestions? Has anyone replaced the drive unit? Is it possible, or will I have to replace the entire NAV unit?

Thanks