| The battery tray has to come off to do the belts. Depending upon year, there's often an earth strap to the regulator or one of the battery mounts. Check this isn't hanging loose. Check also they've coonected the alternator feed back up to.
There's also a large metal cased multi plug on the frame rail just above the tray. This could have been disturbed?? It's the main link between front and rear looms. | 
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