Door speakers don't work, dash speakers do work?
 

Just bought a 1999 Boxster and the only problem I can find is the dash speakers work but the door speakers don't. Does that mean the amp in the front trunk is out or something else?

RADIO
+12V DC Battery(Constant) Red/black B2 7.5 Amp Fuse holder B
Switched Accessory Orange E1 7.5 Amp Fuse holder E
Ground Brown
Power Antenna White
Remote Turn On(output) Black/red
Illumination Gray/blue
Mute Yellow/black Telephone mute
Left Front + Green/red Line level output
Left Front - Brown/blue Pin C1-3; common audio ground
Right Front + Violet/red Line level output
Left Rear + Yellow/red Line level output
Right Rear + Red/blue Line level output

AMPLIFIER OUTPUTS
Wire Function Color Note Fuse # Size Location
12V DC Battery Red/blue D9 15 Amp Fuse holder D
Remote Turn On (input) Black/red
Left Front Mid + Green
Left Front Mid - Brown/green
Left Front Tweeter + Yellow In-panel speaker
Left Front Tweeter - Yellow/brown In-panel speaker
Right Front Mid + Violet
Right Front Mid - Brown/violet
Right Front Tweeter + Red In-panel speaker
Right Front Tweeter - Red/brown In-panel speaker
Left Rear Mid + White
Left Rear Mid - Brown/white
Right Rear Mid + Blue
Right Rear Mid - Brown/blue

I'd start by trying to "pop test" the door speaker.. Use a Battery (Drill, or 9 volt), + of the batt on the + of the speaker wire and the - of the batt on the - of the speaker wire.. If the wiring going from the stock amp to the speaker, and the speaker is good. you'll hear the speaker "pop".. If it does.. the Amp may be to blame.. If it doesn't.. You've got an issue with the wiring or the speaker itself.. Above is all the wiring for the radio and the amp. Hope this helps..

Make sure you un-plug the amp. Use some extra speaker wire and put that into the output plug of the amp on the wires your testing. That way you won't risk damaging the amp if its still good.