Hello. I have searched everywhere and I don't seem to be able to find anything relating to my radio issue. I have read through several different forums, so I will try and answer all of the questions I read from other posts.

I just bought a 1993 Coupe. The radio did not work when I purchased the vehicle. I DO NOT have the Bose system. I have the base Delco system. The time does not show when volume button is pressed. In fact, nothing ever displays on the LCD whether the radio is on or off. Antenna does not go up and there is no sound from a motor even trying. There is no static either or any sound coming from the speakers. It appears as if the head unit is completely dead aside from the backlight being illuminated. The backlight remains illuminated infinitely unless I remove Fuse 40 or remove power to the CDM.

I have checked all fuses with a multimeter and visually inspected/replaced fuses (to be thorough) relating to the radio. Zero issues here.

I have the manual climate control. The horn works just fine. I have no SYS light or constant PKE light. (Again, just trying to be thorough). All other functions appear to be operational. Vehicle runs great.

I found a video testing voltage to the connector at the CDM and got 12v at the constant wire, 12v at the wire for when ignition is switched on, and nothing at the third wire which I guess powers the CDM itself (all this information is from Factory Car Stereo Repair). Of course, this video is dealing with the Bose system, as is everything else I could find relating to radio issues. I'm not sure if that changes anything for my system.

Additionally, I have C72 and H72 in Module 1 (LCD dimming output signal circuit open or shorted to ground). This would make the backlight never shutting off on the radio make more sense, would it not? Most of the posts mention this code is usually thrown once someone tries to replace the factory radio. However, mine is the stock radio and although it is an older vehicle, I doubt the radio was ever touched as the gentleman I purchased the vehicle from is older and the car wasn't driven much. I'm not saying it's impossible, I'm just willing to bet it hasn't been touched.

Hopefully, that covers all the information needed to help. I am leaning toward a bad CDM, but the 72 code threw me a curveball. Could a bad ground cause a radio to illuminate, but not do anything beyond that? Or does a 72 code further point to a bad CDM? Anything else I forgot to test or mention in this post? I just want to make sure before I shell out $200 for a used CDM. If I was keeping the vehicle, I'd likely pull the head unit and replace/upgrade especially since it's not the Bose system. However, I plan on giving the car to my dad for Christmas and he would prefer the stock radio most likely. This should answer the, "Why don't you upgrade?" question.

Thank you!

 

Stereo in my 90 wasn't working when I got it also. I have the Bose Gold with cassette and CD and wanted to keep it stock. Think this a common problem with Bose from these years. Capacitors in the CDM, radio head and speakers over time leak on the electronic boards and cause all sorts of issues. I contacted Factory Car Stereo repair located in Florida. Have a web site which is very informative. Guy's name is Bob. Very pleasant and was easy to work with. Sent him all the components over time starting with the CDM and finally got the stereo working again. It's a good system when working right. Here's the link to the web site if you're interested.
Car Stereo Repair, Factory Car Stereo Repair Inc. and Bose Repair (carstereohelp.com)