Question

Please what could be the reason why  I am having a red battery light come up intermittently on my 2007mercedes-benz-gl450 even after changing my battery, alternator and fan belt. 

Vehicle
Odometer
210000

Answers

If you've replaced the battery and alternator, then there shouldn't be any voltage issues.  However, you should check the bolts on the alternator and the terminals on the battery to make sure they aren't loose.  A loose connection can cause the same problem you have.