Mitsubishi Repair: electrical, advanced auto parts, mitsubishi diamante

Question
93 mitsubishi diamante-all accessories,including headlamps do not come on unless the car is running.i pulled the positive cable off to check the altenator and the car died. if the alt is bad, and the car is running on just the battery, why when i turn the lights on, the interior lights do not dim like the should if the car is running on the battery.  it is a relatively new battery but i just drove about 30 miles with the air on, the radio playing and so on and still the appears to be no power loss in the battery.  i wonder could it be the wiring to the alt.  i did replace them about six months ago.  i appreciate any help you can give me.

Answer
Eric,
If none of your accessories come on without the engine running, there could be a problem with the wiring going from your battery to your accessory harness.  If your battery is strong enough to start the engine, it should still be good.    If it was bad wiring from alternator, many times that would cause your car to hesitate and idle rougly.  But it could explain your battery not charging as it should.

I'd recommend first confirming that your battery and alternator are producing the amount of power they should.  If you have them in your area, take your car to AutoZone, PepBoys or Advanced Auto Parts.  Either of those should be able to do a free test of your battery and alternator.  AutoZone is usually the most accomidating.  They will hook a diagnostic machine up to your alternator and battery to test it's stregnth.  If they determine your alternator and battery are fine, you may need to take your car to mechanic to have the ignition harness inspected.  That harness contains all the starter, accessory, and ignition wires.  Sometimes those harnesses can pull loose or wires could break loose from the harness.
Good luck!