wiring up a headunit correctly
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=105521
Printed Date: April 28, 2024 at 7:51 PM
Topic: wiring up a headunit correctly
Posted By: twinpawer
Subject: wiring up a headunit correctly
Date Posted: June 17, 2008 at 3:42 AM
Hi there,
I've just installed a head unit, and it is working quite fine. However, I've seen another similar head unit wired up in another friend's car, that was installed by a workshop.
On my headunit, if I turn the head unit on, and then start the car (turn the ignition), it switches off momentarily or sometimes dims, until the car starts (due to current consumed by the starter motor, i presume?). However, on his car, it does no difference and the stereo stays on playing music, without any interruption while starting the engine. I've had 2 different head units, and both did the same thing while starting.
Another thing, on his stereo, as soon as he turns on the 'accessory', it powers up automatically. Are these features of a stereo, or is it a wiring issue?
Any info regarding the wiring would be greatly appreciated :)
Thanks!
Replies:
Posted By: i am an idiot
Date Posted: June 17, 2008 at 6:14 AM
Most older cars (I am not sure if the newer ones do this) turn off all other electrical items when attempting to start. Air conditioner radio and etc. They do this so the starter can have all available energy to start the car.
Posted By: twinpawer
Date Posted: June 17, 2008 at 5:31 PM
My car is a ford fiesta 1992, and its wired directly to battery (yellow and red wiring shorted together), and it does it. I don't think it switches off any thing automatically.
My brother has a car which I installed it on, and its a Seat Ibiza 2002, and it also does it.
Note that the radio is not switched off, but like low on power, since the display appears very dim, and as soon as the engine starts and the starter motors stops turning, it will light up as normal again, without the need to press the power button.
My friend has a Volkswagen Polo 1996, and it stays 'on' all throughout ignition, without any problem. Any ideas?? :/
-------------
Posted By: techman93
Date Posted: June 17, 2008 at 6:07 PM
Most radio's even OEM will not stay on while cranking starter. It is hooked to an accessory wire.
-------------
The wire I'm test'n isn't doin' what it's supposed to be doin'... I am so glad I printed that tech sheet, with the wrong info.
Do it right the first time... or I might have to fix it for ya
Posted By: twinpawer
Date Posted: June 18, 2008 at 2:49 AM
Do you think its because it is not connected to the accessory wire? However the Seat Ibiza is connected to it's accessory wire, and its still doing the same, i.e losing power while cranking the starter.
-------------
Posted By: KPierson
Date Posted: June 18, 2008 at 6:34 AM
Grab a volt meter and see how far your battery voltage is dropping when you crank. Most likely your voltage is dropping pretty low and the unit is shutting itself off because there isn't enough power available. The circumstance you describe is NOT a function of the radio, its a function of the environment in which it is installed. If the red and yellow are both connected directly to the battery it should not shut off during cranking. ------------- Kevin Pierson
Posted By: twinpawer
Date Posted: June 18, 2008 at 8:27 AM
yes, the yellow and the red are connected together, however it shuts off during cranking! I saw my friends car that was not shutting off, and wondered if it was a wiring issue. So there's nothing wrong with my wiring?
Also, any idea what the 'Illumination' wire should do, if connected?
-------------
Posted By: haemphyst
Date Posted: June 18, 2008 at 8:46 AM
The starter can pull hundreds of amps during cranking. It would not be surprising to me at all to see a deck nearly turn off, even if wired directly to the battery. Battery age, condition, capacity, connections... all will have dramatic affect on how much the accessory will suffer. I would re-check ALL CONNECTIONS IN THE SYSTEM, including all grounds, (both chassis and engine) and all positive connections. Also, have your battery load-tested. Here in the states, nearly every auto-parts store will load test them for free.
I wouldn't worry about it. If it remains on, albeit in a reduced "on" mode, then your connections are right, and the issue is elsewhere. If the red wire "sees" less than around 10.5 volts, the deck is going to turn off, they're usually built to do so; that is a safety feature, so you aren't left stranded - when the deck turns off, you need to start your car.
As far as the accessory wire, I haven't seen anything since about 1979 that the accessory wire ISN'T interrupted during cranking. Pretty much all cars do that, now. If you mistook your accessory wire as a power wire, then when you crank the starter, it is GOING to turn off.
The illumination wire dims the display on the face of the deck, if there is an illumination wire available in the car. The car's illumination wire turns on with the dash lights, but not all cars are going to have them.
-------------
It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
Posted By: techman93
Date Posted: June 18, 2008 at 6:38 PM
OK let me try to explain again.
Radio's have a constant memory wire for presets and clock, if it has one. The other is accessory 12v when vehicle is running or key in accessory position. I have seen almost all vehicles have their radio shut off during the crank cycle to divert all power to the starter. That is the way most car systems operate if they are original equipment or not. You should not hook up the radio with the red and yellow connected together. Not unless you want the radio to be on at all times with out the vehicle on if they are hooked up to a constant 12v source, or you will lose memory of stations preset into FM/AM bands and the clock will always reset if both are connected to an accessory power source every time you start your car.
During my 12+ years of installing no radio stays on during crank, not unless it is wired that way or a car manufacturers special way of vehicle wiring.
-------------
The wire I'm test'n isn't doin' what it's supposed to be doin'... I am so glad I printed that tech sheet, with the wrong info.
Do it right the first time... or I might have to fix it for ya
Posted By: twinpawer
Date Posted: June 18, 2008 at 6:53 PM
my friends car is a VW polo, and it does not turn the headunit off while cranking, I've seen it myself!
Why should't I hook the radio up with the RED / yellow together? I prefer the radio to be on all times, without the need to turn the key to the accessory position, thats why I connect the red and yellow together.
-------------
Posted By: haemphyst
Date Posted: June 18, 2008 at 8:14 PM
haemphyst wrote:
The starter can pull hundreds of amps during cranking. It would not be surprising to me at all to see a deck nearly turn off, even if wired directly to the battery. Battery age, condition, capacity, connections... all will have dramatic affect on how much the accessory will suffer. I would re-check ALL CONNECTIONS IN THE SYSTEM, including all grounds, (both chassis and engine) and all positive connections. Also, have your battery load-tested. Here in the states, nearly every auto-parts store will load test them for free.
I wouldn't worry about it. If it remains on, albeit in a reduced "on" mode, then your connections are right, and the issue is elsewhere. If the red wire "sees" less than around 10.5 volts, the deck is going to turn off, they're usually built to do so; that is a safety feature, so you aren't left stranded - when the deck turns off, you need to start your car.
As far as the accessory wire, I haven't seen anything since about 1979 that the accessory wire ISN'T interrupted during cranking. Pretty much all cars do that, now. If you mistook your accessory wire as a power wire, then when you crank the starter, it is GOING to turn off.
The illumination wire dims the display on the face of the deck, if there is an illumination wire available in the car. The car's illumination wire turns on with the dash lights, but not all cars are going to have them.
------------- It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
Posted By: i am an idiot
Date Posted: June 18, 2008 at 8:22 PM
If both wires are ran to the battery, the only reason for it shutting down or dimming is the fact that the starter (as stated earlier) pulls hundreds of amps. Having a weak battery could cause this dimming or turning off issue. Before you go run out and buy a new battery, try this. With a good set of jumper cables, connect your vehicle to a friends car. With his engine running, start your car. If it does not dim while connected to his battery too, you should look into a new battery. But I do have to ask this. What is the problem with your radio turning off for the brief time you are attempting to start your car?
Posted By: techman93
Date Posted: June 18, 2008 at 11:25 PM
If you forget to shut off radio you will kill your battery and get stuck.
-------------
The wire I'm test'n isn't doin' what it's supposed to be doin'... I am so glad I printed that tech sheet, with the wrong info.
Do it right the first time... or I might have to fix it for ya
Posted By: twinpawer
Date Posted: June 19, 2008 at 2:45 AM
There's no problem with it :) Its just that my friend's car didn't do it and I thought I'd ask about it. As for forgetting the radio.. well I think one must be quite dumb not to hear the sound coming from the radio, and switching it off before going out :)
My battery is less than a year old, and should be quite good. What I'm sure is that the starter motor does take quite a good amount of charge, as its a large one because my car is quite difficult to start on cold mornings. And its also a Diesel - I was told diesel are more difficult to start than petrol engines?
-------------
Posted By: i am an idiot
Date Posted: June 19, 2008 at 6:34 AM
Why yes, I too have heard that diesel engines are a little harder to start than petrol engines. Maybe that is why the larger diesel engines in the U.S. have 2 batteries.
|