78 Bronco Radio Wiring

Hey all

This is my first post here. Working on a 78 bronco and need to know about the radio wiring. there are three wires (not counting the speakers), orange, white and black. I figure the black is a ground, butwhat are the orange and white wires?

Thanks in advance....

West

One of them is +12 volts switched, and the other probably an illumination or dimmer wire. Use a multimeter to verify ALL the wires though.  I'd recommend just taping off the illumination/dimmer wire as they are usuallyy more trouble than they're worth.  The black one is not necessarily ground though, it might very well be a dimmer/illumination wire.

This vehicle does not have a +12 volts constant wire in it, nor does it have an existing ground wire in most cases.  So you have to run both of these connections yourself.  The ground connection is cake--just find a spot of bare metal behind the dash that's free of paint and dirt.  The +12 volts constant wire can either be run via a fused wire going directly to the positive battery terminal, or you might be able to find a spot at your fuse box.

Always test all the wires with a DMM before connecting to them, especially since you don't know which is power and which is dimmer/illumination.

oh yea I almost forgot....the speaker wiring in this car is almost definitely common ground, which means that there's not a separate positive and negative for each speaker.  Instead, the left front and left rear use the same negative wire, and the right front and right rear use the same negative wire.  Each speaker does have its own positive wire though.