[goldse]

WOW.... 3 Pages and NO Answer ???

Ok, Just to let you know you don't have to use a Relay for powering up your cathodes. Each cathode transformer draws about 0.7 amps of power at 12 volts.
So unless your running 8-9 transformers a relay is OVERKILL.

You can run 1 wire (The switched Ground wire from the dome light) to the ground of the transformer directly, Then use a Constant Hot from the fuse block under the dash. That's how I did mine when I had my focus, then I wanted the Ability to leave them on all the time so I put switches in later.

Hope this helps !

Troy.