70 Challenger Speaker Issues

[dkt711]

Hi everyone.

I am at the point of getting the stock AM/FM thumbwheel radio in my Challenger working. I have the 3 dash speakers and 2 rear speakers setup along with the front/back fader and the crossover box. Everything is hooked up and I have double checked all wiring, but I am having the following issues:

The left rear speaker works great.
The right rear speaker does not work.
The left and right front speakers do not work.
The front center speaker works.

I can switch between front/back speakers (those working), using the fader switch. I also believe the left/right knob on the radio is working (at least when the knob is set to left).

Any ideas? Does it sound like a crossover box issue or bad output from the head unit or ???

Thanks in advance!

[pschlosser]

The cross over can certainly be the issue, but so may the speakers.  For some, the cross over is the more difficult thing to repair.  It controls where the sound goes from a stereo input from the radio.  It's easier to rule out speakers that no longer function, they are easier to test.  And if you can confirm all your speakers work, even through the wires at the cross over, you'll know for sure it's the cross over.

The variable knob rheostats can get noisy and/or stop working after 50 years, so those may have to be checked, electrically.  Rotating the knobs fully one way, then the other, about 10 times each, may clean things up enough to hear if all the channels functions (once you know the speakers are working)

If the speakers work, but not the cross over, it will have to be removed and cleaned/serviced/tested on the bench.

[dkt711]

Thanks for the reply.

I verified all speakers are working. Rotated the knobs/wheels fully one way, then the other way, multiple times. Still no sound when the balance knob/wheel was fully in the "right" position.

A question on the speaker outputs from the radio... There are 3 wires: green, violet, and black. Wondering what each of the 3 wires are for? I think the green is positive for rear left channel, the violet is positive for the right rear channel, and the black is the common negative, but not 100% sure.

I tried hooking up different combinations of those wires with a speaker with the following results:

Attaching the violet and black wire to the speaker, sound.
Attaching the green and black wire to the speaker, no sound.
Attaching the green and violet wire to the speaker, sound.

Does this mean that maybe there is no signal from the green wire from the radio? Trying to rule out the radio as being a possible problem with the right channel before digging into the crossover.

Thanks!