93 crown vic electrical problem

Battery light comes on and stays on. Fuse #15 (instrument cluster(battery warning light) and abs brakes blows. Sometimes the alternator shows 14.5 amps (charging). Other times the alternator reading is only 12 volts(not charging). Replace the 10 amp fuse in fuse box under the instrument panel and all is well until the next time it blows. New battery and new rebuilt alternator. Changed the headlight switch with 93 Grand Marquis spare part. Drove some twenty miles or so with voltmeter connected. Alternator charging and fuse did not blow. Has anyone else experienced this problem. Please note that the 30 amp fuse in engine compartment power distribution box never blows. Thanks.

A 10 amp fuse that pops only some of the time is almost always a wire touching ground somewhere on that circuit, not a bad alternator. That fits what you saw: when the fuse is blown you lose the charge warning light circuit, and the charging looks like it quit too.

Since that fuse feeds the cluster warning lights and the ABS, the short is on one of the wires it powers. Look anywhere a harness can rub: behind the cluster, along the steering column, the warning light wire that runs out to the alternator plug, and the ABS harness under the hood. The headlight switch swap probably just happened to line up with a quiet spell.

A good trick for finding an intermittent short: put a test light (or an old sealed beam bulb) across the fuse slot in place of the fuse. While the short is there it lights up, and you can wiggle sections of harness and watch for the light to go out when you move the bad spot.

The 1992-1997 Crown Victoria wiring page here has Ford's charging system diagram for these cars, which shows the warning light circuit, and the fuse page has the junction box charts so you can see what else that fuse feeds:
https://www.supermotors.net/reference/ford/crown-victoria/1992-1997/wiring-diagrams
https://www.supermotors.net/reference/ford/crown-victoria/1992-1997/fuse-relay-charts

Dana