99HT

I have very little info on the C4 Bose system. If I was sent a Bose HU that at least the radio worked, a system wiring diagram and a good/bad amplified speaker, I will check it all out and do a write up on doing mods to the system. It may be possible to use a the C4 HU with aftermarket amps and speakers without buying an expensive level converter.

I realize there are a number of different C4 HU's, but lets keep this experiment limited to a 90's HU for now.

I asked for C5 components about a year ago, and the good people on the forum sent me all the various C5 Bose components to reverse engineer and help develop my postings. These posts have helped many people modify and improve their C5 systems. The number of emails I get, shows me that many people are using this info. I bought a BCM so that I could bench test the C5 HU out of the car. The C5 HU will not power up out of the car without a BCM connected to it.

R23HTC

Hopefully someone will step up. I see you've been very helpful on the C5 side of things and think it's absolutely wonderful that you'd be willing to help the C4 owners out also. Especially in this day in age when everyone wants to be paid for every little thing. I would have sent you what I had, but as soon as I made a post about replacing the BLOSE with something else, my E-mail was flooded with offers to buy the old stuff, no matter the condition. I sold everything for enough to get my front Infinity Kappa compontents! :yesnod: You'd be the first person I contacted if I wanted to update a C5 stereo. I think what you are offering now is :cool: ! :cheers:

99HT

The advantage I have is that I can take even broken equipment and reverse engineer it. I prefer equipment that works, because I can reverse engineer it a lot faster. It is difficult to sell busted stuff normally, but of course on ebay you can sell trash and someone will buy it and get stuck with it. Delco equipment is a real pain in the butt because no parts have real manufacturersw numbers on them.

99HT

Due to the aount of C4 stereo questions, my offer of reverse engineering the C4 Bose interface still holds. Anyone who wants to donate a bad HU and amplified speaker can do it and contribute to the cause.

-=Jeff=-

99HT,

how many amps will you need? would they be returned when finished? the amps for the 84-89 and 90-up are similar (will work with each other) I may have at least one Front amp when I pull my car apart within the next couple of weeks.. but have no head units. email me jdebuhr@home.com and let me know

99HT

I can use one amp to do the job. Having a HU with at least a functional radio will be the biggest aid. I can take it apart and power it up on the bench to measure signal votages. I can also generally figure out what integrated circuits (IC) are used in the audio interfaces. Delco unfortunately has all IC's, even standard off the shelf ones, labeled with internal part numbers. If I have the wiring diagram of the C4 from a service manual, it will also be very helpful.

The real goal is to allow C4 owners to junk their Bose amplified speakers and use aftermarket amps and speakers without having to buy expensive level converter modules.

I personnally hate ergonomics of most of the aftermarket HU's. They require you to look at the unit and make selections. I like lots of ***** and buttons. I can operate my C5 HU without ever looking at it.

-=Jeff=-

I will post when the amps are out of the car


[Modified by -=Jeff=-, 11:22 AM 10/5/2001]

R23HTC

I would think you know it 99HT, but just in case, you are aware that the radio is a completely seperate piece from the HU in our C4s? You'll need both pieces.

99HT

I have very little knowledge of the various C4 systems. Is there not a number of different HU's depending on the year of the vehicle? Not all were two piece Hu's were they? 1984 to 1996 is a longtime.

R23HTC

From what I gather (not confirmed), the stock C4 HU that was "GM" size, had the radio in the head unit. The stock C4 HU that was of DD size didn't.

-=Jeff=-

84-89 Bose systems had the HU with everything.. tuner and all (one piece) and 4 seperate amps..

90-96 had the 2 pc HU (seperate tuner box) and 4 seperate amps.

I know for a fact (I tried it) that the 90-newer Bose amps will plug in and work with the 84-89 systems.. they even look the same..

I still have not pulled my amps out.. I should have them out this wekend.. I hope. Again you are welcome to have one for your intended purpose

99HT

Thanks for the info. I just thought that since very little info seems to be available on the C4 system, that a FAQ like the one I made for the C5 system would be useful for people wanting to add on to their present system. I really have no need for myself to know this data. Without more info than I have now, I will not be able to do the FAQ.

Since I have a 99 FRC that came with the POS non-Bose base cassette system, I had some incentive to want to upgrade my system and retain the functionality and looks of the Delco HU. I personnally hate using most aftermarket HU's. They require too much interaction and visual cues to operate. When I am at high speed, I like to be able to control my HU with one finger in between shifts without looking at it. I HATE buttons, I love *****.

I was told by my dealer, Delco, GM and everyone on the forum that I could not use the Bose HU in my car. Well they were all wrong. Due a quirk in the design of the C5 Bose/Delco HU and system versus all the other Bose systems I had ever seen, I was able to make the HU work all by itself without external power amps. In the C5 system the only external power amps are for the sub-woofers and all equalization is done in the external Bose signal processor module. Bypass these modules and you have a normal Delco HU with internal power amps and the bonus of pre-amp outputs. My car and a number of other FRC's have no subwoofers, external amps or signal processor. I have even taken it much further and made about 50 component changes inside my HU to remove the "Bose modifications". These modifications make the HU sound somewhat shallow if you don't have a sub-woofer.

My goal was to make my C5 FRC system sound better than the Delco premium sound system in my C2500. It does in spades using the modified Bose HU, aftermarket speakers and nothing else. It is louder than most people could stand with low distortion.

Jeffvette

I have the unit out of my car, everything works but the CD player (go figure). Funny thing is, it has been repaired once before.

I'll be more than happy to donate it as long as I get it back in the same condition I sent it out in. Could careless if the CD player worked.

99HT

If the statements above are true for a 1990 Bose system, I will need both modules to do testing. If I can get a wiring diagram, I can make an temporary interconnect cable to get the modules to powerup.

Could anyone make a copy of the C4 stereo system wiring diagram out of their service manual?

I will return the units after testing.

gcrouse

No offense, but why would anyone want to reuse the Bose HU or speakers when there is so much decent equipment available?

R23HTC

I e-mailed Glock'94 to see if he could respond with what you need. He has the service manuals.

GlockLT4

Lemme find the diagram, and I'll post it for you.

99HT

"No offense, but why would anyone want to reuse the Bose HU or speakers when there is so much decent equipment available?"

I dont think that many people want to re-use the Bose speakers, but many would like to use the stock HU and get better sound. Some would like their car to look stock and others want to just have fun tinkering with the system. If you buy new speakers and new amps, you can always in the end buy a new HU.

I have been building my own stereo equipment since I was a little kid, I am 45 now. I still have a rack mounted component stereo I built from scratch in college in the mid 70's just to show up my roomate who's family bought him a expensive system. I made copies of British stereo gear that I wished I could afford. I had to lay out and hand etch the circuit cards and make the different chassis. I even built the turntable. My job for the last 25 years has been designing electronic products for various companies. My hobby became my work. I still design and build things for my own use that would be much cheaper to buy from a store. Beside the modified Bose HU in my C5, I designed a audible shift indicator. It beeps when I hit 5800 RPM.

GlockLT4

here's what I had in my '94 service manuals....

99HT

Glock'94


Do you have the diagram of HU connections to the display/CD unit?