Brake fluid won't cause the charging system light to illuminate, though. You have a charging system issue. I've heard about many auto parts stores testing alternators and saying they're good, but they fail to load test the alternator, at which point the alternator fails. The alternator and charging system need to be tested on the vehicle for results to be accurate. First, load test the battery and confirm that it is good, as well as making sure the battery cable connections are clean and tight. Make sure the circuit between the battery and the "BAT" connection at the back of the alternator is good. You should have battery voltage there. If not, check the fusible link. Also, check this wire for resistance; it's not uncommon for this circuit (typically a white, 10 gauge wire) to corrode or get overheated and develope resistance in it. Obviously, make sure the drive belt is properly adjusted. With the key "on," charging system light should illuminate. Start the vehicle and test the voltage using a voltmeter. A good charging system will usually put out 13.2 to 15.0 volts, depending on make/model. If this is good, load the charging system by turning on some electrical items, ie high beam headlights, rear defogger, etc. Recheck the voltage output and confirm that it is still within range. If not, you need to replace the alternator. In general, I don't like to use aftermarket starters or alternators on Asian makes as I've seen to many of them fail...if not initially, then not long after installation. Safest bet is to pay a little more and get a genuine Nissan reman part.