Battery.........is that running? If so IT IS NOT CHARGING or the alternator is not keeping up with the fans.
IF the battery v is "running" then the higher voltage at the alternator post indicates that there is a voltage drop in the harness, a BIG one.
I quote this article a LOT. Some folks don't like how it's done, but whether you do this 'as per article" or take another route, this article DOES give a very good overview of the problem:
Catalog
The simplified diagram in that article:
View attachment 1715130063
Gives you a VERY good "view" of the trouble points in these girls. EVERY SINGLE TERMINAL POINT mentioned below must be checked, and by that I mean "with a voltmeter" to "bracket" the area of concern. In no order the troubles are:
terminations at and the fuse link itself
BIG trouble is the big red and big black ammeter/ charge wires going through the bulkhead connector
The ammeter itself, internally, as well as defective/ loose terminals at those ammeter wires
The ignition switch connector
The contacts IN the ignition switch itself
In very rare cases (but it happens) the "welded splice" can fail. This is a factory welded splice in the black ammeter wire, up under the cluster, which feeds off as shown in the diagram.
