12v constant power.... not there

fatgtr · Post by **fatgtr** » Sun Jul 03, 2005 12:12 pm

hey there
in the process of putting my new headunit in. now the red wire ignition 12v is sweet its working. BUT the yellow wire. there is no voltage. i have checked the fuses, plus the cigarette lighter and clock go so it cant be blown.
should i tap into another constant 12v? if so where bouts from.

DeeCee · Post by **DeeCee** » Sun Jul 03, 2005 12:32 pm

you say the red 12v is sweet, but that 12v should come on when the ignition is on..

I'd say you have tapped the 12v ignition to the red wire, instead of the yellow

Yellow = 12v constant (on all the time)
Red - 12v igntion (starts the unit up when the ignition is turned)
Black = Ground

That should sort you out better

fatgtr · Post by **fatgtr** » Sun Jul 03, 2005 1:34 pm

no. what happens is i can turn the key on to acc and there is 12 volts (in the red wire). when i turn the key off and take it out, the yellow wire which should have 12v allways, doesnt. its wierd cant pinpoint it, it has like 40mV

im thinking this car had a handsfree mobile thing installed, could this be the problem?

DeeCee · Post by **DeeCee** » Sun Jul 03, 2005 1:41 pm

okay then, what loom are you wiring to? most toyotas have a blue with yellow strip wire off the factory headunit loom that is the constant 12v.

1. check connections - on the factory 12v constant
2. check ground while attached to 12v constant.
3. run a seperate power wire from the battery to the headunit with an inline fuse on it.

If you are using factory ground i suggest finding another grounding point.
i assume you are are using a multimeter to test voltage from factory 12v constant wire - check what you are grounding the other probe to. I have had issues in the past finding a suitable ground with the probe..

Seriously failing most of this stuff - just turn to point 3.

i can only troublshoot so much over an internet forum expecially if i cannot physically see what the problem is.

Best of luck

DC

fatgtr · Post by **fatgtr** » Sun Jul 03, 2005 1:55 pm

yeah will most likely have to try number 3.
yes i was using a multimeter just touching the wires onto the ends of the probes. i got a reading that was good with the igntion wire using this method. so ill try another ground.
thanx

z|gen · Post by **z|gen** » Sun Jul 03, 2005 4:15 pm

wire your red wire (acc) to the ciggie lighter, and the earth there as well, and then wire your 12v constant - yellow to the 12v constant at the ignition or to the battery

fatgtr · Post by **fatgtr** » Wed Jul 06, 2005 6:05 pm

what if i were to tap the 12v constant into the 12 ignittion? i woulnt have any radio station memory, but i dont listen to the radio.

so yeah will that work

toyonut · Post by **toyonut** » Wed Jul 06, 2005 6:11 pm

it should work, but you wont store settings either so your sound is set to flat every time you turn on

z|gen · Post by **z|gen** » Thu Jul 07, 2005 12:47 pm

your ignition will have a constant 12v+ so why will you lose memory?
all my stereos iv wired in have been to the 12v constant on the ignition and i never lose memory, if you have a test light, probe your wires with the key off and out of the ignition when the light glows, youv found your 12v positive.

GNR · Post by **GNR** » Thu Jul 07, 2005 6:49 pm

zgen you got it around the wrong way, as you said, u you tap the ignition wire and constant into the cars constant, you won't lost memory, becuse the headunit is always on

but as fatgtr said, if he wired the ignition and constant into the cars ignition, the headunit will reset/lose all radio stations and presets.

best to find the right wires, do it properly, and do it once

z|gen · Post by **z|gen** » Tue Jul 12, 2005 11:57 am

so that means i reset everything on my headunit? i dont think so..
i suggest you get your facts right and look at what i wrote.

matt dunn · Post by **matt dunn** » Tue Jul 12, 2005 12:40 pm

z|gen wrote::roll:
so that means i reset everything on my headunit? i dont think so..
i suggest you get your facts right and look at what i wrote.

Correct. It will not lose the memory,

but it also wont turn off when you turn the key off,

and will also drain the battery when sitting as most modern stereo's even though you turn it off on the face,
the internals are still drawing power.

B1NZ · Post by **B1NZ** » Wed Jul 13, 2005 5:31 pm

DeeCee wrote: check what you are grounding the other probe to. I have had issues in the past finding a suitable ground with the probe..

i've found if this is the case just put the probe to the key in the ignition :wink:

DeeCee · Post by **DeeCee** » Wed Jul 13, 2005 6:01 pm

B1NZ wrote:
DeeCee wrote: check what you are grounding the other probe to. I have had issues in the past finding a suitable ground with the probe..

i've found if this is the case just put the probe to the key in the ignition

cheers b1nz - i'll remeber that if i can't find a ground in a honda :lol: