[reporter000001]

so this is a 78?

EDIT: this circut should be powered by the brown wire off your ignition switch......the newer trucks diagrams in this book arent that accurate, you can get a voltage tester/multimeter and test it to ground, thatll tell ya... but the 75 and 77 say the wiper and radio are on the same bar, so if u have wipers, you should have that circut as well.