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1990 C4 Radio Adapter Harness

 
Old 03-10-2019, 10:59 PM
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Default 1990 C4 Radio Adapter Harness

Hello, all. I certainly hope I am posting in the correct place.

Anyway, I purchased my '90 L98 a few weeks ago, and now it's time to update from the factory stereo, which does not appear to be the Bose unit. It says Delco, so I assume that's what it is. The only real issue I'm having is locating the proper wiring adapter to connect the aftermarket radio to the vehicle.

The vehicle has two individual male connectors that connect to two individual female connectors on the stereo. I have found (and mistakenly purchased) a couple of different wiring adapters, but neither fits these male connectors, and neither has two individual mating connectors (should have been a clue, but .... well, ok). I've scoured the internet as well as I know how, and I can't seem to find anything that matches the vehicle. The manufacture date is 11 / 1989, so I even figured I'd check on 1989 parts, since it's an early production year car. No luck there, either. So, for the moment, I have no radio at all in the car, awaiting some solution to this matter.

I was going to sign up for this site anyway, so I guess now is a good time. Can anyone provide any insight into this? I'm sure someone out there has changed out one of these stereos before, so there has to be some solution. I'm just not finding it, for some inexplicable reason.

Any thoughts?
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Old 03-11-2019, 01:51 AM
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I recently purchased a '91, and I'll be doing the same thing very soon. I haven't ordered anything from Crutchfields for this one yet, but I've dealt with them on a few other installations, and they always seem to have the adapter harnesses that are needed. Mounting kits as well. They list one for my '91 with the Bose system. Look them up on line, and if you still don't find it, give them a call.
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Old 03-11-2019, 06:49 PM
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Originally Posted by RedRedRed View Post
I recently purchased a '91, and I'll be doing the same thing very soon. I haven't ordered anything from Crutchfields for this one yet, but I've dealt with them on a few other installations, and they always seem to have the adapter harnesses that are needed. Mounting kits as well. They list one for my '91 with the Bose system. Look them up on line, and if you still don't find it, give them a call.
Oddly, Crutchfield claims to have nothing that fits my vehicle........

Thanks, anyway.
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Old 03-12-2019, 06:45 PM
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Old 03-12-2019, 07:31 PM
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I'm sorry, no.

I'm probably going to get it hard wired. I've got a guy going to take a look at it this evening. I certainly don't like paying for something that's usually as simple as a car stereo, but if that's what it's going to take this time, so be it.

I do appreciate the attempt to help. Thank you.
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Old 03-12-2019, 09:55 PM
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Well, mystery solved. Also explains why the cable Best Buy sold me is like 100 mi long.

It's not supposed to plug into the cables behind the dash. The stereo mounts in the dash, then that long cable routes to the tuner in the *back* of the car. Those two cables under the dash are not used at all.

So, I gotta figure out which side the tuner is on, then work out how I'm going to route this cable. Hopefully, I can route it under the console, because I'd much rather not try going under the dash to the door sills.

This is gonna be "fun" ........

Thanks, everyone, for the responses. I do appreciate it.
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Old 03-12-2019, 10:23 PM
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Originally Posted by BlackMagic_1990_L98 View Post
Well, mystery solved. Also explains why the cable Best Buy sold me is like 100 mi long.

It's not supposed to plug into the cables behind the dash. The stereo mounts in the dash, then that long cable routes to the tuner in the *back* of the car. Those two cables under the dash are not used at all.

So, I gotta figure out which side the tuner is on, then work out how I'm going to route this cable. Hopefully, I can route it under the console, because I'd much rather not try going under the dash to the door sills.

This is gonna be "fun" ........

Thanks, everyone, for the responses. I do appreciate it.
If you're referring to the CDM, it's mounted on the passenger side behind knee bolster (on a '90)... on later years it's under one of the two rear storage compartments. I'm assuming Bose or non-Bose is the same as far as where the CDM is.
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Old 03-12-2019, 11:37 PM
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I could be wrong, but I thought only the Bose system had a separate head unit and a CDM mounted elsewhere. I thought the standard non-Bose system was a traditional head unit with integral amplifier mounted in the dash.

Ether way, Bose or Non-Bose, Crutchfield does offer harnesses. If you select a 1990 Vette with Bose or without Bose as your vehicle, then select receivers and click on any receiver it lists, there's a link right above the price labeled something like "discounted installation equipment." If you click on that, it brings up a package of mounting hardware, wiring harness and instructions, the whole package for about five bucks with the receiver purchase.
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Old 03-13-2019, 12:10 AM
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Thank you, RedRedRed.

Upon closer inspection, it actually is a Bose. For reasons I can't explain, they have AC Delco in huge lettering with Bose in very small print beside it. Easy to miss, which I did.

YouTube says the tuner is in the passenger footwell, as the previous poster, who's name I can't currently access suggests. I'll try to verify the exact location I need to access, then hopefully get to work on this over the weekend. I hate to miss Auto Club race weekend, but I also don't like having my car half torn apart inside, so I'd like to get this over with, one way or the other.

I'll update everyone, and again, thank you all so much.

Last edited by BlackMagic_1990_L98; 03-13-2019 at 12:12 AM.
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Old 03-15-2019, 12:03 AM
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Okay, so after a lot of YouTube and forum reading, I figured out what to do, and thankfully, the hard part is done. I've got the bypass harness hooked up and in. There was basically a metric [bleep] ton of cable, so I found a pretty large open pocket in front of the passenger foot well and hid most of it in there. Hopefully, that's a safe location. I don't see any indication that it's not.

The power antenna isn't hooked up, yet, but I broke the antenna off the other day, anyway. What can I say? I haven't had a car with a telescopic antenna in about 20 years. So, in the meantime before I fix the antenna, just going to wait to hook that up. I don't actually plan on listening to terrestrial radio anytime soon, anyhow. I have a Sirius antenna that I'm a lot more concerned with.

So, it appears, for now, all that's left is to mount the radio, hook it up, route the Sirius antenna, and put all the interior panels back in place. Hopefully.

Thanks, all.

Last edited by BlackMagic_1990_L98; 03-15-2019 at 12:04 AM.
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Old 03-15-2019, 03:25 AM
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Well, I've got everything - radio, bypass cable, Sirius antenna, mic - all installed. No puffs of smoke.

Power seems good, everything lights up as expected. However, no sound. Not sure exactly why, either. The best lead I have came from a YouTube video of a guy in Northern Europe replacing the radio in his '90. He had an issue where he didn't get sound until he hooked up the power antenna lead, which I have not done yet. Thing is ... for lack of a better way to put it, he didn't seem entirely competent, to me. So, I'm not completely believing that.

Does that make sense? No sound until the power antenna (blue / white) cable is connected? Mind you, I wasn't going for airwave radio. I was trying to play over Bluetooth, and it was definitely connected; the track title was displayed, and the clock was running. It just seems odd that it would expect the power antenna to be connected to play sound from another source.

Any ideas, folks?
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Old 03-15-2019, 09:12 AM
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At least in my '92 the power for the antenna relay also powers the amplifier relay. Without it you won't get sound.
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Old 03-15-2019, 11:45 AM
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Originally Posted by JimLentz View Post
At least in my '92 the power for the antenna relay also powers the amplifier relay. Without it you won't get sound.
I was wondering if it was something like that. Makes sense.

Just to confirm my understanding ... The pink wire in question for the power antenna is the same pink wire on the connector that used to plug into the CDM that is now plugged into my bypass cable, correct?
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Old 03-15-2019, 12:43 PM
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Yes, if you can find where the pink wire splits off for the antenna relay you can install a switch inline like I did to disable the antenna at most times. You can also remove the antenna relay from under the trim in the back of the car if you think you will never use the antenna.
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Old 03-15-2019, 02:34 PM
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JimLentz, was your power antenna extended at all times whenever the car was on, or did it only come up when you switched to the radio as your source? I'm curious why you installed a switch. Thanks.
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Old 03-15-2019, 05:16 PM
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Originally Posted by Maldini View Post
JimLentz, was your power antenna extended at all times whenever the car was on, or did it only come up when you switched to the radio as your source? I'm curious why you installed a switch. Thanks.
The antenna went up when I turned on the radio. I mostly listen to MP3 files so want to be able to disable the antenna most of the time, so I placed the switch under the arm rest.
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Old 03-15-2019, 09:32 PM
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Can anyone tell me precisely which pink wire I'm supposed to be splicing into? I tried the one I described above (one of the connectors that used to plug directly into the CDM, but is now plugged into the bypass cable), and that does not appear to be correct. I'm clearly doing something wrong here...........
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Old 03-15-2019, 11:15 PM
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You never said if the original system worked be fore you "upgraded" it. If it didn't work before, and you're using the same speakers, it could be that the original Bose speaker/amps are dead. Each speaker has it's own amp which tends to fail over time. You never mentioned replacing speakers.

I could be off base; I'm not familiar with the bypass cable you're talking about (haven't dug into my system yet), but it sounds like if you didn't have sound before and still don't with a new head unit, the speakers might be the culprit.
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Old 03-15-2019, 11:26 PM
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Originally Posted by RedRedRed View Post
You never said if the original system worked be fore you "upgraded" it. If it didn't work before, and you're using the same speakers, it could be that the original Bose speaker/amps are dead. Each speaker has it's own amp which tends to fail over time. You never mentioned replacing speakers.

I could be off base; I'm not familiar with the bypass cable you're talking about (haven't dug into my system yet), but it sounds like if you didn't have sound before and still don't with a new head unit, the speakers might be the culprit.
The factory unit worked.
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Old 03-16-2019, 12:46 PM
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again, make sure its grounded and I think its thru the ant. best of luck.
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