1997 Ford F-450 Alternator won't charge battery;

The mechanic replaced my alternator in my RV with a new one and when mounting it sparked 3 times (he hadn't disconnected the battery cables). Since putting it in now the charge gauge on the dash doesn't rise but very little and the alternator is not charging the battery. We switched to another alternator thinking that one got shorted out but have same problem. Think it must have blown a fuse but checked the fuse boxes under the dash and under the hood and they tested okay. What are we missing and where do we look and what do we look for? The problem must have been caused by the sparking.