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Discussion Starter #1
I am installing a system into my 2011 Mazda 2 and I am getting what seems to me an odd voltage reading on my rca cable that will plug into my 4 channel amp. My amp can take high level inputs via the RCA input (only has RCA inputs and Pioneer includes a speaker wire to RCA adapter) so I cut the stock front speaker wires coming from the stock head unit, connected a run of 18ga speaker wire to them, then connected them to the Pioneer supplied RCA adapter. When i measured the RCA plugs with my voltmeter, I measured positive on the center pin and negative on the ring. The right channel read out at 3V but the left channel read out at 23V. I tested this with the car key turned to ON but not with the car running. I had the radio on a radio station that was just static. Is this normal? Seems wierd to me. Any idea?
 

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Sounds like your line out converter is knackered and needs replacing

I will also say that it also depends on what was playing when you measured though, ideally a sine wave at a set frequency (50-60hz is good for a test as multimeters are often designed to be accurate at mains frequencys, and not above and below)
 

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Discussion Starter #3
Sounds like your line out converter is knackered and needs replacing

I will also say that it also depends on what was playing when you measured though, ideally a sine wave at a set frequency (50-60hz is good for a test as multimeters are often designed to be accurate at mains frequencys, and not above and below)
Im not using an LOC. My pioneer can take speaker level at the RCAs. It even came with a speaker to rca adapter for the occassion. Good point on the sine wave idea. I will test it using my phone to see if that changes it. Until then, im afraid to hook up the rcas to my new amp.

If the rcas are not hooked up to anything, when driving is there a risk to the car's electrics until i get it fixed?
 

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So it’s just a set of rca plugs with speaker wires attached? No boxes or anything inline?

In that case either your stereo is very odd or your source was not suitable for being measured as you did, test again with a sine wave otherwise your pissing in the wind sadly ??
 

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How confident are you that you connected the RCA adapters properly? Did you solder, are the connections covered to prevent shorting?
 

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So it’s just a set of rca plugs with speaker wires attached? No boxes or anything inline?

In that case either your stereo is very odd or your source was not suitable for being measured as you did, test again with a sine wave otherwise your pissing in the wind sadly ??
I just tried the sine wave test and the voltages stayed the same (3V right channel, 23v left channel. I did notice however that the when the car key is only turned to accessory with radio on, that the right channel still shows 3V, while the left channel shows 0V. But the moment you turn the key to ON or start the car, the left channel jumps to 23V and stays there. All the while the right channel stays at 3 volts.

Of note, in the stock wiring, the left door had 2 wires to the speaker, red and white, both with silver dots running on them. I followed the door wire bundle to under the dash. Where i cut into the wire loom under the dash there was only 1 wire that matched those speaker wires. But, under the dash those speaker wires were each now spirally twisted with a black cable i assumed that was for noise cancellation and were for some other part of the car. Would that have anything to do with this issue?
 

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Discussion Starter #7
How confident are you that you connected the RCA adapters properly? Did you solder, are the connections covered to prevent shorting?
I was sure to connect the positives and negatives properly. I soldered all the connections and used heat shrink and well as electrical tape over the heatshrink.
 

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See if you can get your hands on a wiring diagram with color codes for the radio outputs. Something doesn't seem right at all
 

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Discussion Starter #9
See if you can get your hands on a wiring diagram with color codes for the radio outputs. Something doesn't seem right at all
I checked online and 2 places confirmed that the wires i cut into for the speakers are the speaker wire colors. Do you think the black wires that were spirally twisted have anything to do with it? The right channel wires i cut into werent spirally twisted with any other wires, but they were thicker because the right side stock speaker had 4 wires going to it. So the two wires split into 4 at some point. But the left channel apeaker only had two wires going to it.
 

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The stock signal wires are usually twisted to help block noise ! So, yes, they are speaker wires.
Jesus, they could be can wires, airbag wires or any other form of twisted pair... your response is almost like the only twisted pair in a vehicle is a speaker wire

I’d be taking the speaker wires from the stereo end of the loom... 23v with a sine wave and changing voltage when the ignition is switched on says they ain’t what he thinks they are especially if measured with a sine wave

To the OP, check at the back of the stereo and get the speaker wire there, see if that location behaves the same with ig off and on, defo don’t just trust the wires because they are a twisted pair
 

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I'm not Jesus, but close.
Twisting pairs of wires is only done to help reduce induced noise into the wires.Wouldn't make sense to do it to anything except speaker wires.
 

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I'm not Jesus, but close.
Twisting pairs of wires is only done to help reduce induced noise into the wires.Wouldn't make sense to do it to anything except speaker wires.
That’s all good then... canbus wires clearly aren’t digital signal wires at all... good to see you have massive (sarcasm!!) experience of cars and are willing to pass it on... typical of people who have no clue about what they are talking about yet are willing to comment on...
 

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You'll get no argument from me.

Jesus would be a possible expletive if the airbag goes off.
 

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Discussion Starter #15
So, i might have found the issue. Apparently the left channel pos speaker wire looks EXACTLY the same as one of the airbag wires that hooks into the drivers seat. There are no white wires connect to the seat airbag so i think i got the negative for the speaker correct, but i may have cut the wring wire for the positive. I'm going wire those wires under the dash back to thier original connections and just pull the head unit and tap from there. Ugh, what a pain. Lol
 

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Why are you not using some type of interface between the headunit and the next component such as a T-harness and speedwire, or similar, etc ?
 

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Glad an air bag to the face didn't ruin your day.
Why are you not using some type of interface between the headunit and the next component such as a T-harness and speedwire, or similar, etc ?
Using a T-harness can make things easier if available but having a wiring diagram is the only thing needed if you don't plan on returning things to stock. Luckily the color code assumption didn't cost him way more money than taking it to an install shop would have.
 

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Discussion Starter #18
So it connected the wires back to where they were originally. So all good there. I pulled the head unit and tapped into the left front channel speaker wires from there.

Now on the left channel of the RCAs i am seeing the same voltage as the right channel, 3V...but the left channel is showing -3V. I rechecked the wiring and its all positive to positive and negative to negative, so im not sure why its -3V. Should I switch the positive and negative wires where they connect to the RCA adapter?

Another wierd thing..just before i cut the left channel wires and soldered my speaker cables to them, the head unit played music through the rear speakers fine since that wiring was untouched from stock. But once i wired in the left channel wires, the rear speakers became silent. I didnt touch or mess with the rear speaker wires at all. My RCAs seem to be getting voltagefrom both front channels, so im not sure why the rears suddenly stopped working. Any thoughts?
 

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What wiring diagram did you used to ensure you are taping into the correct wires?
Did you have fader control before?
There may just be one common ground or negative signal for each side. Again wiring diagram would let you know this.
 

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Discussion Starter #20 (Edited)
What wiring diagram did you used to ensure you are taping into the correct wires?
Did you have fader control before?
There may just be one common ground or negative signal for each side. Again wiring diagram would let you know this.
I used this: 2012 Mazda 2 Car Stereo Wiring Diagram - MODIFIEDLIFE

Couldnt find any wiring diagrams online. But the above seems to match the colors i saw coming from the rear of the head unit.

I did have fader control before. I can't tell if the front channels play until i hook up the amp, but they are getting voltage. Fader set to all rear still doesnt make the rear speakers play.

If we cant figure this out, would the easy option just be to get an aftermarket head u it with rca outputs, run an rca cable to the amp and then not connect the front speaker wires on the harness adapter at all? Would that solve everything?
 
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