Again -Before you go any farther, be sure the the electrical supply is stable
Battery, Alternator, Cables - Everything. Especially the B+ supply cables that run
from the battery to the fuse boxes. This doesn't require any codes, just common sense
and the knowledge and ability to use simple meters. It aint rocket science...
A mechanic that knows the ropes should be able to do this in minutes.
Unfortunately, it seems like there are more and more wrenchers out there that
have never learned about the basics. They've become so dependent on "codes"
and repair software, that they don't know how to check the obvious.
But be assured, the good guys are out there!