Answering my own question

I did find a wiring diagram for that radio, and will provide it to anyone who needs it.

The reverb switch has three positions, and it turns out OFF means front speaker only, REVERB means front and rear with reverb active, and REAR means rear only.

I also made a drawing of the switch with the positions of the six wires that connect to it, and will keep that in case anyone else runs into this issue.

Dan Hinnah

 

Answering my own question

I did find a wiring diagram for that radio, and will provide it to anyone who needs it.

The reverb switch has three positions, and it turns out OFF means front speaker only, REVERB means front and rear with reverb active, and REAR means rear only.

I also made a drawing of the switch with the positions of the six wires that connect to it, and will keep that in case anyone else runs into this issue.

Dan Hinnah

I’ll take a copy if u still got it ,thx! jetzster

 

Just want to add to this thread, I had a reverb not working on my 65 GTO. Found a guy in New Jersey who rebuilds them. He even has parts to rebuild the dash reverb switch. He knew his stuff, mine came back working like new. Took about two weeks turn around once he gets it. His name: Howard Foulds (973) 800-4565

 

One thing to note is the reverb switch’s “Center middle position-REVERB”Only puts the reverb effect on the back speaker audio,however, it should still turn on the front speaker audio , but with NO reverb effect.
Thats how you get the correct
Balance of the two sounds to create the lush echo “fake Stereo” effect, (that’s all there was avail till ‘66-67 when cooler sounding two channel FM-stereo radios came into the scene, after that the reverbs were discontinued, prob also cause the reverb amps delay-spring transponders were sensitive, and broke pretty easily from the cars bouncing effect...

Now If both speakers put out the revrb echo effect At the same time,it would be hard to understand radio people talking and you’d hear the music with too much echo going on to make sense of it...

position one-(Off) is front only-no reverb, position 3-(REAR) is rear only-no reverb, so just remember, you should never hear any reverb from the front speaker, just it’s plain sound when in pos-OFF or pos-REVERB,
And in pos-REAR you should hear only t
he rear speaker’s audio with no REVRB.

Added a hidden RediRad-AM modulator and works slick as snot, as it’s Aux input jack allows possibilities , like for you to stream all online or stored music thru a tiny inexpensive Bluetooth receiver module (that can link to any smartphone) ,and one can play CDs/& FM from a tiny portable CD-FM Unit also hidden in the glovebox.
All goes into the AM Radio
When it’s tuned to 1000khz, and then out thru the original reverb system.

So with no obvious mods on the old radio, now can Hear music from the ‘60s-70s just like it was played and heard then, (instead of nowadays Crappy AM Stations) , with the added reverb effect if desired.
It is a highly recommended unit that works well on both the Original AM and FM radios.

 

Here is a typical Delco Reverb switch and unit

After pulling out factory male connector from radio,
The new MALE black connector goes into the radio, the FEMALE connector goes into the MALE factory cable that WAS plugged into the radio.
You can see it loops-thru the radios +12v power on the BLUE wire , and also half taps the Blue +12v thru the Red connector into the switch to be used For the Reverbs power.
It also loops a solid BLACK wire for a radio ground.

The GREEN is the Original radio Front speaker output from radio ,that will now go into the switch. Switch then sends the Front speaker output audio back out on a solid BLACK to the FEMALE connector, and sends out the new Rear speakers output on the WHITE-STRIPED BLACK wire to a separate single connector.
This wire and a ground wire, need to get to the rear speaker with 2 separate at least 16 gauge wires under the floor , or it can be just one wire ,if the rear speaker has been already grounded to frame on one side, usually like the front speaker is.

(With no Reverb From the factory , the Front speaker usually is just grounded on one side to the frame, and has just a single GREEN wire going to it coming out of the radio , and there’s usually a Blue wire going into radio with keyed 12v, and usually a Black ground wire goes into radio Also)

The three combo connector red-green-black -goes to the 10’ long 3 wire pigtail jumper on the left of pic ,under the floor, back to the reverb unit now mounted in the trunk on back of rear seat ( green-input , black-output,red-12v)

Now mount switch under dash and it’s complete.see previous post for 3 position switch Settings. May need to just cut and hard-wire splice some of these wires thru if your radio has different plug connector, but it should still work..
I believe the back 6x9 speaker added should probably be a 10 ohm like the front speaker, (Ames sells them) as most auto speakers were 10 ohm at the time.In the 20% rule, an 8 ohm could work ok, but it is making the radio work harder for the same sound level, hence the newer type 4 ohm speakers would definitely be big trouble for any older original radio. If the volume sounds way down or tinny possibly you have an impedance mismatch, so it needs to be verified that the rear speaker load impedance works and transfers soundz correctly from the reverb unit and radio before all the work of installing.

A good idea would be to just tempy wire all the things together on the floor and test that everything works well first!

Ideally one can also add an aftermarket speaker enclosure around it for even better cool, one of a kind , Classic Reverb soundz!
Hope this helps..

 

My reverb box was missing when I bought the car. Where is it mounted on the 68?

 

Not sure for sure about a ‘68 but I believe most were just under the rear center speaker on some small alum L-bar on back of rear seat, I used rubber grommets On the bolts to help cut vibration down on the springs inside unit.

 

Not sure for sure about a ‘68 but I believe most were just under the rear center speaker on some t-bar on back of rear seat
View attachment 134056
View attachment 134057

Thanks!!

 

What year is your car?

As an FYI, the 68/69 Reverb unit was mounted above the glovebox with a special bracket which was shared with the stereo multiplex unit.
The brackets are different between 68 and 69.
The switches are different.

Amplifiers were different between 64-67 and 68-69.
Reverb option discontinued in 1970

The service manual has a wire outline for all the radio options in the accessories chapter.

 

What year is your car?

As an FYI, the 68/69 Reverb unit was mounted above the glovebox with a special bracket which was shared with the stereo multiplex unit.
The brackets are different between 68 and 69.
The switches are different.

Amplifiers were different between 64-67 and 68-69.
Reverb option discontinued in 1970

The service manual has a wire outline for all the radio options in the accessories chapter.

Why do the pics show it mounted below the rear speaker in the trunk?

 

That is for pre-68 units.

 

Here is for the ‘68 (and I assume ‘69) units, mounted above the glove box like O52 stated. Diagram is from the 1968 Service Manual.

 

Here is the mounting location for 64-67

Here is the mounting location for 68

 

Here are some wiring diagrams for the 68 audio options

Reverb

Rear Speaker. There are two different switches for the 68 rear speaker. Depending on which front and rear speaker you have (single or two terminal) and whether factory or dealer Installed.

Stereo Tape Player

Stereo Multiplex Amplifier

 

My cousins 68 GTO had the reverb unit in the trunk, does that mean that it was dealer installed?

 

The 68 reverb unit was factory installed in front, above the glove box, so could be but doubtful. I believe prior years were installed in the trunk, maybe it was a pre ‘68 unit that a prior owner installed.