Hello All,


After finally getting my head unit and speakers installed I thought I'd give some helpful hints to aide you in your project. While doing my research I realized that while there is plenty of information on how to install a head unit and speakers in a C4, there aren't any specific guides on how to do it in a 1990 corvette. I wanted to put this up so that maybe the next persons project can be a little smoother than my own. I did this install on a 1990 C4 Corvette Coupe with a Delco-Bose Gold head unit. I hope someone gets some use out of this.



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The Equipment I Used
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- Head Unit = (I used a single din JVC unit with aux/bluetooth/usb - Not sure what the make and model are but I will update as soon as I check)

- Rear Speakers = (I used two 6.5 inch kenwood speakers. They fit into the stock enclosures perfectly and matched up with all of the holes)

- Front Speakers = (I used two 4 inch kenwood speakers. There was a bit of a gap in the fit so it required a bit of wiggling to make it where there weren't any gaps. A problem I ran into while installing these speakers were that they had 4 mounting holes while the stock enclosures only had 3 mounting holes. I had to bend a few things to make it fit but they sit in nicely now)

- Wiring Harness = (I used a Metra Mini Connecter for select GM vehicles. It had all of the wires I needed and matched up perfectly with the 3 plugs connected to the CDM unit)

- Dash Kit = (I am not entirely sure which dash kit I used but I bought it from a car audio installer and it was made for certain models (90 to 93. It fit and works great but it not much to look at)

- Wiring = (I used 14 guage wiring. Very small and easy to move around under the carpet)

- Tools = (Wire Crimper/Splicer/Cutter - Electrical Tape - Socket Set - Flathead Screwdriver - Phillipshead Screwdriver)


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The Steps I Followed
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(((Head Unit)))

- remove front of center console

- remove vents above heat/ac/stereo area.

- remove front of heat/ac/stereo area.

- remove head unit.


(((Rear Speakers)))

- remove the speaker covers.

- remove the speaker enclosures.

- remove the speakers from the enclosure.

- remove the amps and the stock wiring from the enclosure.

- install the new speakers into the enclosure.

- install the enclosures back in place.


(((Front Speakers)))

- remove the pilar panels (Just to the side of the seat).

- remove the side panels (just below the pilar panel along the door sill).

- remove the speaker enclosures.

- remove the amps and the stock wiring from the enclosure.

- install new speakers into the enclosure.

- install the enclosures back in place.


(((Wiring)))

- run wires from the head unit area and connect them to the front speakers.

- run wires from the head unit area and connect them to the rear speakers.

- run wires from the head unit area to the CDM unit location (Under the dash on the passengers side).

- locate the CDM unit and disconnect the three plugs on the right of it (the plugs should be located slightly under and behind the fuse box on the passengers side. If you want to use your radio antenna you will need to pull this unit out to access the wire).

- connect the wiring harness adapter to the three plugs pulled from the CDM unit.

- run the from the wiring harness adapter to the head unit wiring harness and match them according to your specific head units colors.

- connect the wires from your front speakers to the head unit wiring harness.

- connect the wires from your rear speakers to the head unit wiring harness.


(((Finishing Up)))

- connect your battery to test your system to ensure all the speakers and the head unit are working properly (Once you confirm all is working disconnect the battery again).

- install your rear speaker covers.

- install the side panels.

- install the side pilar panels.

- install the dash kit.

- install the head unit into the dash kit.

- install the front of the heat/ac/stereo area.

- install the vents above the heat/ac/stereo area.

- test your head unit/speakers.



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Tips
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- Take your time on the install to ensure the best quality.

- Check all of your equipment before the install to be sure that you have what fits and works in your vehicle.

- Make sure you take all possible safety precautions before starting.

- Be careful with your wiring. A few mixed up wires could possibly cause harm to your hardware.

- Be sure you take breaks while installing.

- Use this forum as much as you can. The people on this forum are very helpful. There are tons of people that have done this before you so they can help you with any questions or problems you may run into.

- For help locating some of the things I mentioned or getting certain items taken apart visit http://www.carstereoremoval.com/. It was very helpful during my install and I am sure it will be helpful during yours.

- Plan for the future. If you are going to eventually add amps or a sub, plan for it now. Run the wires if you have them. Pick your locations. This is the best way to make sure you aren't doing the same job twice.

 

You will probably need to cut the original mounting bracket that is in the back out so it will have a better fit.

Also when you say run new speaker wires are you talking about running them direct to the head unit? If you are not, and your car is like my 89' then you will have to cut a few wires in the harness and directly wire to the harness coming out the new head unit due to them combining grounds to make our lives difficult.

 

Check the audio section for the TSB on resistors that are required on 90+ models when changing heads. A 5 pack at the Shack was less than 3 bux.

 

I will have to make sure I have a tool to cut the mounting bracket when I get out there.

When I say run the new speaker wire I am meaning run a wire all the way from where the speakers are located all the way to the harness of the new head unit and connecting them together. I want to leave as much of the original harness intact as I can. I am hoping that the only wires I will have to cut will be the ignition, accessory, antenna and ground wires.


With that and all of the other things in my checklist in the first post, does it seem like I will be able to do this install? I am assuming that by wiring the new speakers directly to the new head unit harness I can prevent having to touch any bose stuff and the only other thing I will have to do is cut the required wires to power the system from the factory harness.




I just put those on the shopping list. Thank you sir.

 

For the speaker & head change in my 90 coupe I left all the Bose speaker wiring intact.
Sill plates & kick panels removed, new rear speaker wire was fished under the carpet in the hatch using a 3' length of TIG welding rod. A wire coat hanger will work getting it under the carpet. Its been awhile, IIRC I drilled holes for the rear speaker wires to enter the speaker housings.

Removing the electrical connector from the CDM? the tuner unit located behind & above the fuse box is a PITA. I think I removed both seats for easier access to everything.

 

I installed a new Kenwood head and new speakers in my 1992 and no resistors were required. I have had no problems.

 

You can still wire everything like the speakers directly from the new head unit to the speakers but also buy the aftermarket harness that would attach to the original wiring and hook up the other stuff. It will save you from having to cut anything.

 

Ok. So with that being said, and the additional things discussed, if I follow all of my steps up front and add in the things we talked about would that be a recipe for a successful head unit and speaker install? I surely hope so because I've already ripped everything out and put the speakers in the bose enclosures. Just waiting to see if this is it so I can start running the wires.

 

I just did an install on my own. Not sure about your year, but mine had a separate bose "brain" behind the pass seat. They moved them around from year to year.

In my car, I installed a double din headunit, two amps, component speakers, and a sub.

I took the four necessary wires from the bose "brain" harness and ran those to the new headunit. You will also need an antenna wire. If you are running off of an internal headunit amp, run your speaker wires there as well. You will need a few of the wires from the dash as well that run the power antenna, etc...

Depending on the depth of your new headunit, you may need to dremel out the plastic behind where the headunit sits.

You may also need to file down the dash trim that surrounds your new headunit.

FYI, my new pioneer died within 10 secs of install. internal amp error. irony here is that Im using external amps. Knew I should have gotten the alpine...

 

I'm trying to make sure I understand everything you are saying so that I do not run in to any problems after the install. As far as the brain goes, you are saying I have to run wires from this "brain" to my head unit? Does that mean that instead of cutting the wires from the harness that is already connected to the existing bose unit (I have a harness that attaches to the existing harness but I am going to use this to make it simple for other readers) I will have to find this "brain" and run the wires from there instead?

I'm assuming that this "brain" is one harness going in and one harness going out and that I would be cutting the wires from the harness going in and running them to the new head unit.


At the moment I am really trying to keep away from the whole speaker/sub amp and sub talk to make this as easy as possible to understand for myself and others that may be asking the same question so sorry if I ask to many questions or seem to be repeating what you say and expecting an answer.

 

You have a 1990. The head unit is in front of the console. You will be replacing it. The "brain" is the electronics unit. It is under the dash at the passenger end is very difficult to get to. All you will need to do with it is disconnect the radio antenna from it so you can hook it up to the new radio in the dash. You will probably need an adapter to do this. The new speaker wires will run from the head unit to each new speaker. They are easy to install once you remove the plastic trim on the sides in the rear and take some of the carpet loose.

 

I don't know any words that can say thank you better than just plain old thank you. Straight forward and simple. I'm going to head out first thing in the morning and get this thing done.

 

On my 94 I removed EVERYTHING Bose, the only things left were the Antenna and the harness to the head unit, once you identify what wires in this bundle are what, you can then hardwire them into the harness that should have been supplied with your new H/U,no need for more bulky adapters in the dash, limited space in there anyway,provided you have removed the items you intend to replace, tou can forget about separate "brain" units etc, your working straight from the main harness in the dash, thats all you need off the original system, I ran a seperate Kenwood Amp but I guess thats optional, other than that I cant see anything wrong with your planned instillation..

 

So if I am understanding you correctly, I can bypass the "brain" part of the system (I assume I will still need to get the antenna wire from the "brain" like Kmcoldcars said) and just use the harness that is connected to the bose unit, splice the wires (or in my case, since I already broke down and bought the adapter, I can connect the adapter harness to the bose harness) and connect them to the new head unit harness, run my speakers wires to the new head unit harness and have a working system?

 

I reckon so, all I removed was the Bose H/U and all four speakers, provided you match the wires from the new H/U harness to their relative wires in the old harness, things like power supply,Antenna trigger wire etc,you shouldn't need any brain, the new H/U should have all you need onboard, and because your speakers and associated wiring are all brand new then anything from the old Bose system is redundant,so long as you connect like for like as much as possible between the old and new harness's it should be fine, I've just remembered I had to buy an Antenna coax extension cable to reach from the cargo area to the new H/U, straight forward fitting though, well that's how I did mine and it works perfectly

 

Thats what I was hoping to hear. Thank you as well. Very helpful information and information that will be put to use! Hopefully I can have an update by tomorrow afternoon for you guys and maybe a FAQ for this type of situation on Tuesday.

 

Resistors are only needed if the car has the C68 Electronic HVAC controls. 99% of the folks that say they didn't need the resistors have manual controls, I have only heard of 1 or 2 conversions that didn't need the resistors with the C68 option.

 

Thanks for posting your project.

Any pics of the H.U. after the install?

Thanks,

Carl

 

I will post the pics later tonight. I actually need to trim a little bit of the part behind the head unit to have it fit perfectly.

 

Can't wait to see. Also, I am soooo glad mine was just the delco radio!