1999 Subaru Legacy Outback Wagon loses electrical power

I have an electrical issue with our Subaru that the dealership electrical repair mechanic cannot solve. The car was being driven at highway speed, suddenly losing all lights on dash panel, and all guages ceased working with the exception of the fuel guage. Cruise control continued to work. The next morning, the car would not start. It was if the battery was dead. Battery replaced, alternator replaced with no luck. After checking fuses, found blown 10 amp SRS fuse that controls the seatbelt restraint light in the event of an accident. Fuse replaced, started engine, and it blew the fuse again and stopped running. Went through(fried) many fuses trying to diagnose issue. All electrical functions will not work, such as the windows. Car won’t stay running!!!

Here is a list of things that fuse 15 ties to:

A/C switch
Combination meter
Mode control panel
T.C.S. off switch

Combination meter (Airbag)

Blower motor relay
Check connector
Daytime running light control module
Daytime running light relay
Hi-beam relay
Power window and sunroof relay
Seat belt timer

Looking at the list of things I can see why the things you mentioned don’t work but I don’t see why you weren’t able to start the car even with the fuse blown unless the wiring has been modified by someone. In order to find the trouble you could replace the fuse with a load, like a few brake lights tied in parallel. The lights will glow brightly due to the short on the line but the current will be at a safe level due to the load of the lights now in series with the short on the line. You then start disconnecting connectors to the areas shown above until the lights either dim or go out. The problem will be on that connection you just removed. You can then trace the trouble from that connector. You should also be able to replace the fuse back in and the other areas will have power back to them.

It would really help to have the factory wiring diagrams to help you with this trouble. Here is a link you can purchase the info from if you want to.