When issues arise with the navigation system, it also affects the functions of the radio e.g. no ability to change radio functions, such as speaker and tone. This integrated function might be great for manufacturers but it is a pain for the end users especially when the warranty expires. Heater defroster controls should be totally separated from entertainment systems and have individual modules to control them. It's going to be great when the new touch screen controlled vehicles start to die. I never understood why we thought having a tv screen in the dashboard was a good idea!