im actually having a very similar problem, but mine started after being rear ended and im still hunting for shorts.
tail light fuse blows when headlights turned on, and so i cant drive at night (no tail lights, gauge lights)

if you dont mind my asking even after ahving provided no valuable information, wheres that relay located?

1992 22re Toyota 4x4 pickup big speakers, bigger tires. rear ended <img src="/forums/images/graemlins/frown.gif" alt="" />