Knowing nothing about positive earth cars I am curious why you don't want a relay. Seeing the purpose of the relay is to keep the high current in the engine bay and not though a switch on the dash I can't see why a positive earth car would be different, surely the current required for the horn is the same regardless of which way it flows though the car?
Just curious.
Correct, Ohms Law is unaffected by polarity.
BR
Colin
