I just bought an '87 740 GLE about two weeks ago that had given me no problems whatsoever. All of a sudden (and curiously right after I installed an aftermarket stereo) it has developed a weird starting problem. After I had finished installing the stereo I turned the key to start the car and got nothing, the starter motor would not even crank. I figured that since the dome light had been on for a few hours along with the stereo intermittently the battery had been too drained to crank the car over. I pulled out my jump box and the car started without issue. After than I proceeded to drive to school (about 70 miles) thinking that the long drive would replenish the battery. About 1/2 way there I was pulled over by a police officer (70 in a 55...) and shut my car off. Once I got my ticket and the officer was on his way I attempted to start my car-again nothing. AAA towed me home and I got up this morning and put the battery charger on the car for a few hours, lo and behold it started. I tested the voltage across the battery terminals with the car running-12 to 14 volts as it should be. I then tested the output post on the alternator, also 12-14 volts. The battery terminals are tight and corrosion free and the battery is a two month old Interstate. The alternator and starter connections also are good and tight. Any ideas? Could it be a faulty ignition switch? Shouldn't I be getting a battery light if the battery is not being recharged? What can I test to eliminate/narrow things down?

Thanks,

Matthew