Elecrical Problems

Hey techs out there I seem to have a bit of an electrical problem with my 300e Here,S how it goes. The radio,The clock, The inside door lights(the lights when you open the door)The lights on the window switches(when the park light is on)an the vanity mirror lights don,t work when the front passenger door is closed.When the front passenger door is open all the above work fine, Except the Tach which stops when the passenger door is opened. Now I recently installed a Prestige Car alarm in the car, now the alarm seems to be still operating fine, but could this be the source of my problem? I know this is kinda confusing electrical problem but this kinda stuff can only happen to me.

1987 300E