This is the radio for my 70 442. Does anyone have a wiring diagram for the 9 pin plug that goes to the factory stereo amp? I have searched online and in my chassis service and assembly manuals with no luck.

 

The box that accepts that 9 pin plug is not a stereo amp but the FM multiplex and 1 audio output section, the other is in the radio. So, you cannot wire the plug into a stereo amp. You need the specific multiplex box for that radio. Don't quote me, but other multiplex boxes from other GM may work, but the mounting brackets are car specific.

 

Thank you. I'm not looking for a "multiplex" unit. Just interested in the wiring diagram.

Obviously the rear output comes from the "stereo adapter". Therefore linking the fader to the 9 pin harness. Hence the reason I would like to find a wiring diagram for the 9 pin connector.

The other thing I need to know, is if there is an amplified "rear" signal coming out of the 9 pin that needs a resister. Or can I operate this radio without the "stereo adapter" and rear speakers. I only plan to hook up the front speaker, but I don't want to fry it if there are no rear speaker hooked up. I assume it is not amplified, and safe to operate without the stereo adapter.

 

 

This is what you need.

 

Ok, now we're getting somewhere! Thanks. Is there a drawing of the radio unit? I assume that's the multiplex. Mostly, I was looking for a labled output of what each wire does. I assume it's safe to run the radio without the multiplex.

 

The schematic in the first photo is just that of the multiplex unit, not the head unit. The pinout in the second photo shows you that the orange wire on pin 1 is the input for the rear channel from the head unit. Pin 5 is rear speaker output and pin 4 is ground/return for the speaker. I think pins 2 and 8 are where the fader connects.

 

I'm doing this from memory...
From the 1st schematic:
A&B are from the mpx output to the radio's AM/FM switch
C is to the radio's STEREO lamp
D is 12V into the MPX for the single channel power amp
E is 12V into the MPX for the mpx section
F is 1 channel audio from the radio's volume/tone control
G is the feedback of output of the single channel power amp that goes back to the radio's volume/tone control
H is from the FM detector in the radio to feed the mpx
I is the output of the single channel power amp that goes back to the radio and then out to one of the speakers
J is ground

If you want to use the radio as an AM/FM mono radio, it will require some work to make it happen. Meaning going into the radio to connect the FM decoder output to the AM/FM switch and possibly more. Then you can use the radio's internal single channel amp to drive your front speaker.

Frankly, I would look for a mpx box, makes it a lot easier and you'll have stereo. Or, sell this one and get a 71-71 AM/FM mono radio.

 

Thanks for the info. I gave it a try with power and front speaker hooked up. It made static noise, and that was it. I will be running a separate hidden audio setup with bluetooth streaming. I want to leave the factory stereo in place to give it that original restored look, and hoping it works is a bonus. Though I will likely never use it, I hate to have something that doesn't work.
Also, it appears this car never had rear speakers. So without rear speakers, would it come with a multiplex?

 

Understand your intentions.
If the car had the stereo radio factory or dealer installed, it would have had the rear speaker (just 1). The stereo radio always came with the mpx box.
Without the mpx box you should still be able to get AM, but the FM audio is not connected so you'll get no sound.

 

I bought a multiplex box on ebay. Plugged it in and it works! FM restored.

The unit came from a Toronado with different bracket. Does anyone have a picture of a Cutlass multiplex bracket? So I can see how it mounts above the glove box? Holding it in place, I really don't see what it mounts to. Thanks.