You pretty much need to have a volt meter that you can read when this happens, but it is probably exceeding 15.5 vdc, or higher when you get the fault. Load shed shuts down the DD, to protect it from damage. My VR was putting out 18 vdc when I was getting the fault. Since you got the alternator from FCP, it should be covered under warranty.
I saw on Amazon that Bosch has started selling direct to the end user, & cheaper than any other source for their parts. I got a new MAF for 160.00, & everyone else wanted 220.00 or higher. With Prime they are shipping 2 days.
Strange that it would go to zero, but I have seen under voltage faults before. The VR usually puts out excess voltage. The modules are designed to run at very close to 5 volts, anything off of 5 volts throws a fault. Try checking out the voltage at the jump terminal, just to see if you get a different reading?
That does point to the alternator for over & under voltage problems. This would trip the DD warning on the dash. Is that a new, or rebuilt alternator they sent you? The joys of pulling a valve cover in the summer heat is not fun. Are you going to replace the upper timing gasket also? If it leaks at the blocked off pressure port in the upper timing cover, it will pour a lot of oil out, & soak the alternator.
A forum community dedicated to BMW owners and enthusiasts. Come join the discussion about Bimmerfest events, production numbers, programming, performance, modifications, classifieds, troubleshooting, maintenance, and more! Bringing the BMW community together.