1998 750IL Nav System

I own a 1998 750IL with the standard Nav System. Several weeks ago it began failing, periodically blacking out and I had it replaced for a significant amount at the dealer about 3 weeks ago. Unfortunately it has faiked again - blacked out completely again. Once it blacks out I don't have turn signals either. It is going back to the dealer Monday and I would like to know if anyone else has had Nav System failures (I've now had 2) and what the fix was.

I have the same problem. The service manual claims that the Nav. software needs to be upgraded. But I have the latest installed on my 740iL '98. Do I have to make them upgrade it again, I don't know. I am still searching for clues

The second time I returned my 750IL they replaced the instrument cluster - another $500 on top of the $1,700 for the Nav System that probably was not defective the first time. Apparently they can't tell which is the bad part...so they say...so I got the expensive one first and then the next most next. So far it has worked for the few weeks I have had it back. It does sometimes take awhile to come on and occasionally it seems to re-boot itself, but it comes on and works so I am keeping my fingers crossed. One thing I have noticed is that if I use the key fob to open the doors and get the interior lights on the Nav system seems to boot faster than just getting in the opened car (when it is in my garage) and starting it. Another thing the dealer told me was the colder it is the slower the Nav system comes on-line. Not sure how that works because for the last several winters in the Midwest I didn't have that problem with the Nav in the 750IL and never did before in my 740IL. I was never told about getting a software upgrade, but I must have received one because now I have the annoying disclaimer that shows on the screen when the thing boots up and I have to press the control button to accept the disclaimer prior to seeing the menu. The disclaimer was never there before and I didn't have it in my last 740IL which was a 1999. If this doesn't work I was told they'll have to start tearing the car apart and look for a short in the wiring. They told me they would start with the interior...don't ask me why there. I am clearly not up for that so I hope it keeps working. Good luck.