Stereo wiring - yellow constant 12v wire seems dead

[shark525i]

Hey Gang - Just got a new stereo to replace the stock unit and there are a couple of issues I am trying to resolve. First off, it seems like the yellow "constant" 12v power wire has no juice. I put a volt meter on it, turn on ignition, and nothing registers. (in fact it should have juice whether ignition is on or not). When I put the volt meter on the red ignition lead, I'm getting at least 12v. So the JVC stereo wasn't turning on. I went ahead connected yellow power from the head to red power from the dash, and when ignition is on, the stereo powers on as well. So, I think that confirms that the yellow constant from the dash is dead... I have checked all fuses, and everything is fine there. How can my red "ignition" power lead be ok but not the yellow "constant" lead? And more importantly, how do I fix it? I could almost live with it like that, but of course no radio presets or anything would stay in memory whenever I turn off the car.... I suppose one option is run a lead directly from the battery to the new stereo yellow wire...

[wsmc831]

how can one wire not have power and the other one can? simple, they're different wires.

switched power supplies aren't that hard to find, and there is no magic.

test fuses with a meter to verify, then find a different switched lead if there are real problems with that one...

[lhgubi]

Hey Gang - Just got a new stereo to replace the stock unit and there are a couple of issues I am trying to resolve. First off, it seems like the yellow "constant" 12v power wire has no juice. I put a volt meter on it, turn on ignition, and nothing registers. (in fact it should have juice whether ignition is on or not). When I put the volt meter on the red ignition lead, I'm getting at least 12v. So the JVC stereo wasn't turning on. I went ahead connected yellow power from the head to red power from the dash, and when ignition is on, the stereo powers on as well. So, I think that confirms that the yellow constant from the dash is dead... I have checked all fuses, and everything is fine there. How can my red "ignition" power lead be ok but not the yellow "constant" lead? And more importantly, how do I fix it? I could almost live with it like that, but of course no radio presets or anything would stay in memory whenever I turn off the car.... I suppose one option is run a lead directly from the battery to the new stereo yellow wire...

I'm cornfused. Where is the yellow wire connected. I believe it SHOULD be connected to a non-switched 12 volt source. Like the cigarette lighter.

[shark525i]

OK I'm just talking about the wires coming from inside the dash that used to connect to the stock stereo. There is the red power lead tied to the ignition, and the yellow "constant" power lead which one way or another connects to the battery (but how it gets from the dash to the battery, I don't know). The red wire has juice, but the yellow one does not. As a workaround I just connect the stereo to the red wire, but of course cannot save any radio station presets, have the CD resume where it left off, etc, since there is no juice when the ignition is off.

The question then is: which fuse (if any) is associated with the yellow constant 12v wire? (my lighter still works so it isn't the lighter fuse).

[hmsM3]

you dont have a diagram on the back of the fuse panel? look for the radio one (duh) and if you have a fuse thats noted "back-up" double check that one. in my integra that one usually blows if the constant accidently grounds out. that fuse was under the hood. but it may vary from car to car. or have you considered that you hooked it up wrong? you have a 12v tester...start checking other wires if they're hot or not and if you do check DO NOT turn the ignition on if you're looking for a 12v constant!!

[shark525i]

Well the funny thing is - yes there is a radio fuse, but apparently it only covers the red ignition-linked wire. There is no fuse explicitly marked as being for the 12v constant. The radio fuse is ok. Yeah I may have to just check out different wires and fuses, trial and error, until I find the right one...

you dont have a diagram on the back of the fuse panel? look for the radio one (duh) and if you have a fuse thats noted "back-up" double check that one. in my integra that one usually blows if the constant accidently grounds out. that fuse was under the hood. but it may vary from car to car. or have you considered that you hooked it up wrong? you have a 12v tester...start checking other wires if they're hot or not and if you do check DO NOT turn the ignition on if you're looking for a 12v constant!!

[xisco44]

what happen if i connect my headunit, the red and yellow wire on the headunit the battery and acc cable to the constant yellow cable of the car since the acc cable is no where to be found, right now i have it like that but when i turn off the car the radio will keep working but if i turn it off it would discharge the battery because is on standby?

[attack eagle]

Hey Gang - Just got a new stereo to replace the stock unit and there are a couple of issues I am trying to resolve. First off, it seems like the yellow "constant" 12v power wire has no juice. I put a volt meter on it, turn on ignition, and nothing registers. (in fact it should have juice whether ignition is on or not). When I put the volt meter on the red ignition lead, I'm getting at least 12v. So the JVC stereo wasn't turning on. I went ahead connected yellow power from the head to red power from the dash, and when ignition is on, the stereo powers on as well. So, I think that confirms that the yellow constant from the dash is dead... I have checked all fuses, and everything is fine there. How can my red "ignition" power lead be ok but not the yellow "constant" lead? And more importantly, how do I fix it? I could almost live with it like that, but of course no radio presets or anything would stay in memory whenever I turn off the car.... I suppose one option is run a lead directly from the battery to the new stereo yellow wire...

Who said that BMw uses standard aftermarket color codes?
or are you talking about the adapter to standard color codes you used?
http://www.bmwe34.net/e34main/Upgrade/Stereo_radio.htm

Check both fuseboxs for a blown fuse.

[audiodemon]

Check both fuseboxs for a blown fuse.

with multimeter...not just by looking at them.

[RandallPhoto]

Not sure on the BMW but it is very common to tie the constant radio with reverse lights, or some other random fuse, like said before, every fuse in the car needs to be checked with a multimeter

[bmw4dayz]

I have the same problem. I have an aftermarket JVC in my 1984 733i. It has power on the red wire but not the yellow. The radio will not turn on.