C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

C4 stereo problem

Old Mar 25, 2018 | 04:45 PM
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Default C4 stereo problem

When I turn the radio on in my C4, I immediately get a loud buzz/hum like I'm getting feedback. Did a recon on the radio and replaced the amp in the driver's side. What should I be looking for that could cause this hum??
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Old Mar 26, 2018 | 06:29 AM
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What model and radio is in the vehicle?
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Old Mar 26, 2018 | 01:14 PM
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Originally Posted by RICHARD TILL
What model and radio is in the vehicle?
It is the factory original Bose system for a '93 Vette
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Old Mar 26, 2018 | 04:10 PM
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Your EDM may be going out. It is a common problem and a PITA to fix. I replace my EDM and all four amps on my 91. Now the system is good as new.
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Old Mar 27, 2018 | 11:19 AM
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Are there any other possibilities? How would I troubleshoot to know for sure that is the problem?
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Old Mar 27, 2018 | 12:21 PM
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Not many other possibilities as it is a pretty simple system; head unit to EDM to Amp/speakers.

I understand your wanting a different solution but 99% of the time the EDM on these cars go kaput.

The only thing you can do is try swapping your amp with a known working amp. If you speaker works then the EDM is good and your amps are bad.
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Old Mar 27, 2018 | 03:05 PM
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I guess E Bay is my next stop. Thanks!
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Old Mar 28, 2018 | 12:29 AM
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Originally Posted by jimwyn2
I guess E Bay is my next stop. Thanks!
Maybe you need to but ask yourself this. How important is it to you that you have THIS unit working? If you don't care about the radio, leave it alone. If you want a better unit, shell out a few bucks to have some guy break his back for you crawling around there and laying wire for the speakers. That is what I did with Best Buy. I made sure they left a foot on each end extra so I can go home and do the wiring myself. They are young, let them do the back breaking work. You do the soldering part.

Final option is to get someone like Dr Don to fix the parts for you. I don't know him personally so hard to say but others have said he is good. I just dumped the Bose into the trash can and added my own stereo with the modern amenities. Bought brackets for non-Bose and put other speakers in place and it all buttons up nice and neat.

Best part of all is that now I can change the speakers or head unit at whim and not be married to the outdated Bose crap. Yes, it was great at one time but not anymore. Fixing it costs money and makes me have to keep everything Bose. Now that it is gone, no more. I can change the fronts or backs or both and the head unit at will.
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Old Mar 28, 2018 | 10:21 AM
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Originally Posted by jimwyn2
When I turn the radio on in my C4, I immediately get a loud buzz/hum like I'm getting feedback. Did a recon on the radio and replaced the amp in the driver's side. What should I be looking for that could cause this hum??
Is it out of all 4 speakers or just one ?

If its all 4, it might be the CDM and I might have a fix for that. (I just did an inexpensive repair on mine)

Got any electronic and soldering experience ?

Last edited by pcolt94; Mar 28, 2018 at 12:45 PM.
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Old Mar 28, 2018 | 11:13 AM
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I had the same problem.... Speakers/amp. dead....

Installed new speakers/HU after that...


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Old Mar 28, 2018 | 11:34 AM
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Originally Posted by Baddabing
I had the same problem.... Speakers/amp. dead....

Installed new speakers/HU after that...


Slightly used CDM for sale
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Old Mar 28, 2018 | 12:42 PM
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Originally Posted by aklim
Slightly used CDM for sale
good price - only used for 28 years....

The new Poineer HU....


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Old Mar 28, 2018 | 02:22 PM
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Originally Posted by Baddabing
good price - only used for 28 years....

The new Poineer HU....


Why throw good money away trying to keep something alive which hamstrings you in choices when there is much better
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Old Mar 28, 2018 | 03:21 PM
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Originally Posted by aklim
Why throw good money away trying to keep something alive which hamstrings you in choices when there is much better
I ask myself this question every time I spend money on my C4. Not sure why but I keep doing it.....😁
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Old Mar 28, 2018 | 04:37 PM
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Originally Posted by Silver85
I ask myself this question every time I spend money on my C4. Not sure why but I keep doing it.....😁
Pretty simple for me. Spent too much money with upgrades and we don't throw away our toys just because something new and shiny comes along. Play till it is broke then I get to buy a new toy. Rules or we will simply buy things, throw them away when the next color comes along.
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Old Apr 11, 2018 | 05:37 PM
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Replaced the CDM and right rear speaker unit. Still get the loud hum out of right rear speaker. Just had the head unit reworked a couple years age.
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Old Apr 11, 2018 | 07:41 PM
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Originally Posted by jimwyn2
Replaced the CDM and right rear speaker unit. Still get the loud hum out of right rear speaker. Just had the head unit reworked a couple years age.
Did the parts come from a private person or a company?
Do you have any assurance that the parts were checked out or working?

You can always swap the left speaker box over to the right and see what the result is. If it still hums it's (probably) not the speaker box.

Other than the hum, is there any audio or sound that comes out of any speakers?

Can I make the assumption that the radio was working normal at one time and then the problem developed? That would indicate the wiring is OK probably.

You should change one thing at a time or you don’t have a base line or reference as to what is good or bad. More than likely only one item is bad however with new items brought into the picture it makes for more variables.
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Old Apr 11, 2018 | 07:55 PM
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Originally Posted by jimwyn2
Replaced the CDM and right rear speaker unit. Still get the loud hum out of right rear speaker. Just had the head unit reworked a couple years age.
If the other three speakers sound fine, you need to change the AMP on the right rear, not the speaker
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Old Apr 11, 2018 | 08:07 PM
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Originally Posted by billschroeder5842
If the other three speakers sound fine, you need to change the AMP on the right rear, not the speaker
The OP said he changed the speaker unit.....not the speaker.
I take that as the whole speaker box with the AMP in it.
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Old Apr 12, 2018 | 01:44 PM
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Default problem solved! Thanks

Originally Posted by pcolt94
Is it out of all 4 speakers or just one ?

If its all 4, it might be the CDM and I might have a fix for that. (I just did an inexpensive repair on mine)

Got any electronic and soldering experience ?
Problem solved! Thanks1
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