I'm having trouble with the sound system in my truck!!! I just bought it and it already has a crappy job of an after market HU with even crappier wiring!!! Ive looked all over online with no answers to my questions. The truck came stock with only one speaker on the dash. I'm getting ready to put in a new HU and door speakers but i cannot seem to find a constant 12v inside the dash. there is only four wires, 2 for the speaker and then a yellow and a light blue. How do i run a 12v constant or are either blue or yellow wire the constant?

 

in stock form, you didn't have that wire you need, so either the previous installer added one, or you'll need to.

to add one, buy an inline fuse holder, crimp a ring terminal of appropriate size to one of its two wires, and connect that to the battery side of the starter solenoid, then run a new wire of appropriate size from this fuse holder up to the dashboard. you can usually push a few wires through the grommet that holds the main wiring harness over near the steering column, and thats where i recommend routing it. if for some reason you don't do it this way, you can drill a hole in the firewall, install a grommet in that hole, and push the wire through there. most stereos ask for a 10a fuse, which means you'll want to run 16ga wire or heavier and the 10a fuse it asks for. do NOT simply trust the fuse on the back of the stereo itself, as that only protects the unit and not the wiring.

i believe the yellow in the dash is your switched 12v, but you should verify that before taking my word for it.

for your info, the factory stereo did not have a 12v constant wire, but only a switched wire, and that was ok when stereos didn't have an internal clock and various memory needs. but all modern stereos need the 12v constant wire you're looking for. it sounds like the PO didn't bother to do it right.

 

When i installed my hu i got constant hot from the cig lighter. Its a yellow with black stripe.
Pulled the wire down, butt spliced an inline fuse, then butt spliced a wire for the hu and the cig lighter connector to the other end.

 

jayz, that works ok as long as you don't plan to run anything more than a phone charger off the cig lighter plug. i used to run a tiny inverter off mine, and likely that plus the stereo would have either blown the lighter fuse or melted the wiring.

we should remember that modern stereos pull ALL their power off the constant 12v wire, and only use the switched wire to turn on a relay that allows it to turn on.

i'm always hesitant to add any significant load to the stock wiring, as the auto industry has a habit of using the smallest wire they can get away with, so adding even just 5 amps to the wrong circuit can overload a wire without blowing its fuse in some cases.

 

Yeah. But its fused right behind the cig lighter. Easy swap if needed. All i use the lighter for is chargin my mp.

 

I am not sure I agree with the above. I can't say definitively if you are wrong and I don't have a radio schematic in front of me, but it has been my understanding that the constant power is for the memory only just to keep the stations in the radio, and possibly to eject the cassette or cd or some other small task. I thought the main amplifier for the radio ran off the switched power wire. But like I said I can't prove it.

 

i'm pretty sure the way i described it is true at least for the panasonic stereos i've been playing with for several years. i don't know for sure if all brands are the same, but i would expect it to be. i guess someone could test it by putting like a 3a fuse in the battery wire and seeing if if blows when you turn the volume up

 

im sorry guys i feel so stupid about this whole thing!!! never had a vehicle this old. So Josh if i run a 12v from the battery to my HU w/an in-line fuse do i have to run a negative also? if so where do i splice the negative to? if not how is it being grounded? Jayz that sounds like a good idea w/ the cigarette lighter but for some reason my CL kept blowing the fuse idk if it was because it was stuck in if thats the case!!! If so i could just eliminate the whole lighter and use it only for my horn and HU??

 

When you pull the hu look in the hole and there is a metal plate/bracket in there. I drilled a hole about 1/2" in from the edge, stripped a couple inches of wire, fed it throuvh the hole and wrapped it back around its self making the loop really snug. Electrical taped the twists and viola short good ground.

If your already blowing the fuse id be leery about adding an extra load. As franklin said im pretty sure the hu constant hot should be for memory. If you use it id go no larger than a 15amp inline.

If your at all unsure about the status of the lighter wiring and fuse and if it may have a short id just pull a wire from the battery. Just be sure to connect everything snug first before connecting it to power.

 

NO, DON'T USE THE EVIL TWIST-N-TAPE WIRING METHOD

instead, find a convenient screw that goes into a piece of metal and use a ring terminal to connect your wire to it. your local parts store will have all the terminals you need, and they aren't expensive.
as a general rule, all automotive wiring finds its ground to a nearby piece of metal, as nearly every piece of metal on the vehicle should be grounded.

 

And do I run a negative from the battery? Hook it up to the hu?

 

No. Any good metal surface. The plate behind the radio is a good place.

 

On a different topic sorry but I am pulling my cluster apart because the lights don't work and when I pulled the front cover off there is a little blue bulb above the head like and wiper controls and one on the cluster that are constantly on why won't they turn off?? And what is it for?

 

They are your lights. Push the light switch in and they will go off.

 

When you take out your cluster bulbs poke out the blue covers in the holes. They will brighten up your dash alot. Bulbs should be a 194