1999 GMC Truck radio juction block cut off

Tiny
NHENSHER
  • MEMBER
  • 1999 GMC TRUCK
  • V8
  • 4WD
  • AUTOMATIC
I was going to put in a aftermarket stereo in our truck. When I noticed that the radio juction block had been cut off. There are like four dark green wires alone. Then in the processes now I have made my dash lights and gages go out. I am having to do this my self because my husband is disabled and we live on SSI for one and I don, t work becausr I, am his care. Giver. It seem like I messed things all up now. I don, t have a gas guage, no speedometer. All I wanted was a stereo for when I ran shopping an paying bill. Looking online has been no help at all till I found you guys. I hope you can help.
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Friday, October 10th, 2014 AT 10:20 AM

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Tiny
CARADIODOC
  • EXPERT
What was in there for a radio before? I don't know what you're referring to by "junction block".

Are the original radio plugs still in there or did someone cut them out previously?
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Friday, October 10th, 2014 AT 10:10 PM
Tiny
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Thats what they cut was the radio juction block. They had a CD/DVD player in it.I am putting in a eclispe CD/ Radio in. I no what wires go to what on the stereo. But the GMC like I said has 4-5 dark green wires ( no strips) alone. I figured out which ones are the speakers I think. And the stero has of course red for power. But the truck I can, t tell. And now I don, t know what I did but all the dash gauges aren, t working. And my god under the hood you need a PHD just to try to under stand and read the fuse block under the hood. It seem the dash fuses are all labeled ign. But they were all fine. I could only find 3. I am pretty good at trying to figure things out but this truck is confusing. My god why would they have so many danm wires the same color if they weren, t trying to confuse someone. They did it that way so you have to take it to GMC to have them fix it I think. HELP.
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Saturday, October 11th, 2014 AT 1:21 PM
Tiny
CARADIODOC
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GM has a whole pile of very customer-unfriendly business practices that force you to go back to the dealer, but that didn't really get to be a problem until 2002 on a few truck models. Their daytime running lamp circuits are another nightmare. There's about a dozen light brown wires that all look the same. Pity the people at the body shops trying to piece together a crashed car with a bunch of crushed and cut wires that all look the same.

Something that might help is to use a test light first to find the 12 volt memory wire that has voltage all the time, then the "ignition 12 volt" wire from the ignition switch. It will only have 12 volts with the ignition switch turned on or to the accessory position.

If there was an original amp, that had to be bypassed for the radio you removed, so if there was a "switched 12 volt" wire for an amp / power antenna circuit, that was likely cut and taped up already.

Original GM radios have "speed-sensitive volume" where the volume goes up when you increase speed. To run that there's two data buss wires that connect to every computer on the truck. Those will likely be a different color but they're likely also cut and taped up. No aftermarket radio uses them.

Of the remaining wires, there should be eight for the four speakers. If the original plugs are still in the dash and were used with an adapter harness, those eight wires are in two plugs, each with four wires. One is a light green and its mate is a dark green. There is also a light blue and dark blue for another speaker. I can't remember the other four colors but I have a swap meet handout with the colors listed that I can post if I can find it.

If the plugs were cut off, you can use a 1 1/2 volt "D", "C", "AA", or "AAA" cell to find which ones are for which speaker. Grab two wires and hold one on each end of the cell. When you find a pair, you'll hear a little scratching in that speaker. That way you'll know which speaker those wires are for.
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Saturday, October 11th, 2014 AT 11:01 PM
Tiny
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The ignition still works its just the gauges and lights on the dash. Then the stereo has a red (power) then a yellow with a inline fuse. A pink for cell. Truck does not have a power antanna. So what. I need to do first is find out which wires have power. Because the stereo want s power and constent power. As far as the dash goes. Which is my biggest problem. I so scared to drive because I don, t have a gas guage and the darn truck only gets 10 mph. So is it a fuse or one of those cut wires thats the problem?
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Sunday, October 12th, 2014 AT 9:26 AM
Tiny
CARADIODOC
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You missed my point about the power antenna. That is the name of the wire coming out of the original radio. It can also be called "remote amp", but regardless of its name, it doesn't mean you have to have those options on the vehicle.

I forgot to mention that there's going to be two radio wires related to the dash lights. One is tied to the tail lights and tells the original radio's display to dim when the tail lights / head lights are turned on. The second wire is tied to the dash lights and tells the display how much to dim. Most commonly what happens is someone cuts those wires and they touch ground or don't seal the ends of those wires and they vibrate later and touch the grounded radio case, and blow a fuse. There's a fuse for the dash lights that I think is inside the truck, but that is fed off the tail light fuse, and that one might be under the hood.

You will have a red, 10 amp "Gauges" fuse inside on the left side of the dash. I can't remember for sure, but I don't think that affects the lights. If you can run the engine and the generator is working, the "Gauges" fuse is okay.

Be sure the instrument cluster is fully seated. If the mounting screws are removed, the cluster will move toward you a little. That will allow the connector to come apart. It's just a flexible printed circuit on the dash that the cluster plugs into, and it doesn't take much to have bad connections.

You don't have to connect wires behind the radio to make the tail lights or dash lights work. You have to prevent them from touching anything grounded.
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Sunday, October 12th, 2014 AT 11:08 PM
Tiny
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Tail lights are working. Just the gauge lightson the gauges and the gauges them selves. It, s like, let me see how to explain this. I had just got some gas before this happened so the gas guage has stayed at just a bit over half a tank. It has not want off that even though I got gas last night. So its one of those darn (4) brown wires. The ones you told me to check with the multi meter. I do have a nice multi neter I bought. It a Mulewalkie( spelled it wrong hope you can understand what I meant). Is there any way you can write it out like this for each wire

Red : power
Pink: cell phone
Yellow w/ inline fuse:?
And so on for each color. Ut would be much easer to read then trying to figure it out between sentances. Sorry for taking up so much of your time but you have been the greatest help I could find, THANK YOU.
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Tuesday, October 14th, 2014 AT 2:19 PM
Tiny
CARADIODOC
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The only wire colors I have are for the original GM radio. This is a drawing I made to hand out at an old car show swap meet.

I had a '98 GMC truck at my community college that I think is the same as yours. The GM dealers couldn't fix it so they donated it to us. I put some electrical "bugs" in it and some had to do with the "gauges" fuse. I'm on a borrowed computer right now, and thanks to a major house fire, I'm sitting in the library parking lot using their wireless internet. I have the dash gauges information on an older computer at home. I'll try to find that tomorrow so I can tell you what to look for.

All I can remember is it was a red, ten amp fuse, and along with the gauges, it fed the "Battery" lamp circuit that got the generator started. The students ran into additional problems when the instrument cluster wasn't bolted in tightly. The connector is rather unusual and the cluster has to be held in for it to stay connected.

Most likely I can't help with your new radio but I can offer some suggestions. Tell me the brand and about how old it is. I only repair original equipment radios and I specialize in Chrysler stuff, but I do have some installation manuals for a few aftermarket radios.

As a general rule, the 12 volt memory wire is pink. It needs 12 volts all the time to maintain the station presets and clock. The ignition 12 volts from the ignition switch is red. Those two turn the radio on. Once the radio is on, the switched 12 volts wire will have 12 volts on it to power an amp or power antenna if they're used. That is usually dark blue but it could be yellow. If you have any double wires, those will be for the speakers. Most commonly I see a pair of gray wires, white wires, dark green wires, and light green wires. You could also have two dark green wires for a front speaker, and two dark green wires with stripes, (tracers), for a rear speaker.

Some less-expensive radios only have six speaker wires instead of eight. When there's eight, two are for each speaker, one in each corner. When there's six wires, one goes to each of the four speakers, then one splits and goes to each right speakers' second terminal, and the other one splits and goes to each left speakers' second terminal.

In all original radios, and all but the cheapest aftermarket radios, no speaker wire can go to ground like they did in most cars in the '70s. Touching any speaker wire to a metal part of the vehicle will usually damage the radio.
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Wednesday, October 15th, 2014 AT 12:39 AM
Tiny
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Sorry that I have not gotten back sooner. As for the stereo it was easy to find out what colors went to what. The only colors it had were red, pink black, yellow( w/in line fuse) eight speaker wires. I think that there might have been maybe 1or 2 more I not sure its out in the truck and I am in my house. I no the red is power black is ground, pink was for cell and assorey, s. Not sure about where the one with the fuse went. Its just a pain in the but because theres not one single wire that matches up to the truck.
The fuse is not blown and my guages at least the lights have came back on by them self. If I understood u right the red power on the stereo goes to the power on the ingtion switch. I must be really dense. Those 4 dark green trying to figure out what they go to. This whole thing is because that little block that had nothing but radio wires got cut. The only part of my dash that open is where the radio goes in. I am just not understanding where those for green go into the radio at. I am so sorry I am slow. If this would have involved wrenching I would have understood but elect, I have a hard time understanding.
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Monday, October 20th, 2014 AT 8:20 AM
Tiny
CARADIODOC
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Those green wires have to be for something else. The original radio only had one dark green wire for one of the speakers.

In the replacement radio, the constant 12 feed for the memory will be the pink or yellow wire. In this case I think it's the yellow one. They put a fuse in there because in some vehicles it will get connected to a tap in the fuse box that isn't protected by its own fuse.
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Monday, October 20th, 2014 AT 4:22 PM

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