Why?
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Forum Name: General Discussion
Forum Discription: General Mobile Electronics Questions and Answers
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=6315
Printed Date: June 09, 2024 at 7:31 AM
Topic: Why?
Posted By: kparkk
Subject: Why?
Date Posted: December 06, 2002 at 10:19 AM
Why the radio power wiring in any car has ACC power wire instead of having IGN power wire? In other words, Why is it designed for the radio to turn off while cranking the car, and not on all the time when the key is not in the off position?
Replies:
Posted By: Oc768
Date Posted: December 06, 2002 at 10:34 PM
You want as much power available to start the vehicle, same reason (on most) vehicles - no accessories will function when key is in the (momentary) "start" position. In many vehicles there are two "IGN" sets of wires, in this case one set is to the battery, and the other is off an output from a relay connected to the alternator, so that when it is producing voltage, certain systems are enabled (ie: ABS system). As for it operating all the time in the "run" position - if it doesent, there's more then likely a wiring issue somewhere. Its late and Im tired, I hope I understood your question properly (?)
Posted By: kparkk
Date Posted: December 07, 2002 at 8:44 PM
It sounds like right to have all the power just to crank the car, but really how much power a head unit would take, 10A? so is that too much to take away while starting the car? The reason I was asking, is because when you hook up a DVD player in the car, and tapp into the ACC power wire of the head unit, then if ur kids are watching a movie while the engine is off, and then you decide to start the car & keep going, then the DVD resets, and you have to start the movie all over. not fun ... right? So, usually a DVD player should be hooked up to an IGN source in order to avoid such a problem? what do you all installers hook it up to? IGN in the ignition switch wires? or ACC behind teh ehad unit? Thanks for calrification.
Posted By: DeathsJester12V
Date Posted: December 08, 2002 at 2:47 PM
When I do do these types of installs...I hook it up to Acc. hey if the kids are already watching a DVD and are that far into it...what's taking the parents so long? plus in an instance like that, you could put a switch inline with the acc..so that while you are startign your car, you can flip the switch and supply 12V to the DVD player, jsut make sure you switch it off after it's started, or you can do some fancy relay stuff. but it doesn't matter cause the monitors will shut off if they're hooked up to Acc...Plus even if you hook it up to ign. it would have to be ign. 1 not ign. 2. Reason being, usually ( and this is my experience ) ign. 2 is shut off during the cranking cycles. only thing that gets power is ign. 1, which powers the fuel pump, starter and various other component of the electrical system that are required to start the vehicle. And how much current is required to start the vehicle..A lot more than you think. Think about it this way...Tiny device moving huge device, Lots of energy required ( Starter Cranking the engine ) They actually take a hell of a lot of current, more than you think. hence why, if you try starting your vehicle more than six times ( 30 seconds each time )...you notice it's gets very hard, and within 5 minutes it is possible to kill a battery. ( and that's from my Automotive mechanics and electrical systems book I got when i was in college )....what a lot of people don't know or realize, is that thonly purpose your battery serves is to Start the engine. once the vehicle is started, it's all on the alternator, everythign hooked up to your battery is beign fed by your alternator. amplifiers, ligths, radios, etc. All the battery is, is a storage device for energy. Hope that helped a little
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Posted By: webguy
Date Posted: December 12, 2002 at 9:09 AM
Is the memory (12v + constant) connected correctly. It has been my experience that you should be able to pick up on the movie right where you left off, when interuppting power. Another reason why electronic accessories are switched off during the starting sequence is because of the voltage surge that takes place from the starter's current draw. I have always advised the customer not to start the car with the audio system turned on. I have seen a few tweeters loose it from the voltage spike....... ------------- Clean tools = Clean work!
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