Dash light/tail light fuse

I am a newbie, so please bear with me. I have an '02 Xterra SE. I recently installed an FM modulator and had tapped into my 12v power on the dash (where the cig lighter should be). Following that install I keep blowing the fuse for my dash lights/tail lights. Modulator still works when this happens. May be a coincidence but this is the only thing I have changed. I check my tail lights and have even taken the modulator out, but the fuse still blows. Has anyone heard of this happening, or are there any suggestions for a fix? Thanks.