We have discused already that ( thread posted by cnxt )... diode is a must because if not, will result the same than ALLMOT bypass the ballast. The ballast will keep feeding the 86 terminal and that's imposible to save... and if the relay reacts on the ballast feed to coil, will stay on.. adding also more load to the coil circuit, changing the ballast output too... and the 30 terminal won't be getting either 12 volts, but the ballast output

While the relay doesn't react to the ballast voltage, will be nice, but if switches, you will be on a different world.

( not being a smartass, but being logic on how the circuit works )