I'm beginning to think there is something wrong with the harness. Review this simplified diagram, which is from the ammeter bypass article
[URL]http://www.madelectrical.com/electricaltech/amp-gauges.shtml[/URL]
View attachment 1716093588
Bear in mind this is simplified.
In a stock harness, the main feed for the interior comes off the big stud of the relay, through the fuse link, and through the bulkhead on ammeter BIG RED. Through the ammeter, out the ammeter on BLACK, and to the WELDED SPLICE a few inches from the ammeter. From that splice, the BLACK branches off, depending on year
TO headlight switch
TO ignition switch power feed
TO fuse panel hot buss
TO bulkhead connector and out to alternator output stud
So get into your fuse panel, which, (factory) has THREE busses. 1 is hot at all times, 1 is hot only in "run" or "accessory" and the last is hot ONLY when the light switch is feeding power to the INST fuse for the dash lamps.
So find out if one buss in the panel is HOT always, and if not, find out. Check if the other is HOT with key in "run" or "accessory" and if not find out why
