Thanks Meister, I do have a 03 525iT. The dealer told me this mirror was for the e90, e60, and e53 cars. Looking at the ETK parts catalog this mirror was used for european e39s as well.

Can you tell me why this mirror is not compatible? All the wiring diagrams I have been able to find basically show switched power to pin 3 and ground to pin 10 with the side mirror dimming to pins 4 through 7, the alarm LED is on pins 8 and 9, and the reverse signal is on pin 1 to kill the dimming function. The e39 is wired the same as the E53 with the exception that it does not have the side dimming mirrors. Any idea what that retrofit cable looks like or includes? I appreciate your help.