I have a 1968 Bonneville 400 CI, I replaced the Battery, the alternator, and the system still will not charge. Silinoid, coil and alternator are all new within the past year, and it still will not charge.

Any suggestions as to what might be wrong?

 

I had a similar problem with my 66. I'm not sure if this applies to the 68, but may be worth looking at. My system couldn't hold a charge, I replaced the battery and alternator, still same problem. It turns out that my regulator was bad. In addition, the replacement one I orignally got was not correct for 66, even though the book said it was correct. Did some more digging, found a new correct one, and all my problems were fixed!

The regulator on a 66 is the 2x2 inch square on the firewall near the master cylinder.

Hope this helps.