93' 318i electrical problem

I'm having a very confusing problem with my recently purchased 93 318i. The initial problem occurred while braking at low speed. It almost felt like being slightly rear-ended by another motorist.

Since this time, a yellow icon with an exclamation point, inside what looks to be a gear, has appeared from time to time. The air conditioning goes off and the car loses some acceleration and gearing ability when the light is on. The headlights and interior lights seem to pulsate for some reason, which I can't determine.

I have replaced the battery and will soon replace the alternator. Am I on the right track with these repairs, or does the problem have a deeper root like a voltage regulator?

Any help or advice would be very much appreciated.

i think you should have replaced only voltage regulator in alternator insted off alternator assembly.