jonathanc Posted September 16, 2010 Share Posted September 16, 2010 I might have to tap from a fuse for an ignition live feed. However, I am wondering what is the right/safe way to do this? Basically this will power my stereo when the car is switched on. Few questions: 1) Can I just jam a wire to the right side of the fuse instead of using a fuse tap? I can't seem to find them anywhere... 2) Do I have to use the correct rated wire? I have a pretty think speaker wire at the moment... 3) Does the amp rating of the fuse I am tapping into matter? Should I choose a lower amp one? The one I am looking at right now is 10A. Many thanks. Quote Link to comment Share on other sites More sharing options...
SUPRALOOPY Posted September 16, 2010 Share Posted September 16, 2010 What does what you are tapping into draw atm? amp wise? Quote Link to comment Share on other sites More sharing options...
jonathanc Posted September 16, 2010 Author Share Posted September 16, 2010 What does what you are tapping into draw atm? amp wise? It is for my aftermarket HU. The OEM HU uses CAN signals to turn on/off so I would have to tap from the nearby fusebox. I am basically drawing 12V for the ignition live feed to the HU . I am not sure amp wise though... (a bit of an electrical numpty me!) The Fuse I am looking at is a 10A fuse for the A/C. Quote Link to comment Share on other sites More sharing options...
SUPRALOOPY Posted September 16, 2010 Share Posted September 16, 2010 Ok lets say the A/C draws 7 amps what does the stereo draw? If its more than 3amps then you would need thicker wire (depending on the amp rating of said wire) and a larger fuse (15A). Quote Link to comment Share on other sites More sharing options...
jonathanc Posted September 16, 2010 Author Share Posted September 16, 2010 Ah yes, I see where you are coming from now. Well,this (clicky) is my HU. Not sure how to find out how much amps its drawing but there is one 10A fuse on the back? So basically I should replace the A/C fuse to a 25A one just to be safe and get a wire that's rated for that to tap into the fuse? Quote Link to comment Share on other sites More sharing options...
SUPRALOOPY Posted September 16, 2010 Share Posted September 16, 2010 Ah yes, I see where you are coming from now. Well,this (clicky) is my HU. Not sure how to find out how much amps its drawing but there is one 10A fuse on the back? So basically I should replace the A/C fuse to a 25A one just to be safe and get a wire that's rated for that to tap into the fuse? Nope you would not put a 25a fuse in as then if something went wrong you could melt wires. The fuse is there to protect the wires and the unit from dead shorts. try leaving the 10a in and if if it keeps blowing the go to 15a max. Quote Link to comment Share on other sites More sharing options...
jonathanc Posted September 16, 2010 Author Share Posted September 16, 2010 Ah yes, cheers for that....told you I am an electrical numpty... Thinking of using a wire with inline fuse. Hopefully I can find a spare fuse location that has 12V when switched on. If not will an inline wire jammed in the current 10A fuse with another 10A fuse inline work? Is it even necessary at all to fuse the connection? I guess the worse could happen is that I blow the fuse? Shouldn't spark or start any fire I hope.. Quote Link to comment Share on other sites More sharing options...
merckx Posted September 16, 2010 Share Posted September 16, 2010 I'm confused that you're confused. The ignition live feed is there so you basically need to have the keys in the ignition and turned to the accesssory position for your head unit to switch on. This is to prevent the head unit from staying on when you leave the car which would obviously drain your battery. Nearly all cars including the Supra have an ignition live feed in the head unit wiring harness that's in the car behind the unit, it's normally the red wire. I would be surprised that your head unit doesn't come with 2 multiplugs which just plug into the mating connectors that are in the car. You shouldn't need to mess around with fuses and wire sizes for the ignition live supply. Quote Link to comment Share on other sites More sharing options...
jonathanc Posted September 16, 2010 Author Share Posted September 16, 2010 I'm confused that you're confused. The ignition live feed is there so you basically need to have the keys in the ignition and turned to the accesssory position for your head unit to switch on. This is to prevent the head unit from staying on when you leave the car which would obviously drain your battery. Nearly all cars including the Supra have an ignition live feed in the head unit wiring harness that's in the car behind the unit, it's normally the red wire. I would be surprised that your head unit doesn't come with 2 multiplugs which just plug into the mating connectors that are in the car. You shouldn't need to mess around with fuses and wire sizes for the ignition live supply. Mate, I really wished mine came with that magical red wire too but it doesn't My stock HU uses signals from the CANbus to determine if the engine is switched on or off. I could tap into the nearby ciggy lighter but that would involve taking off a lot of trim... the fuse box is a far more accessible option. My car is an 2001 Audi A8 and the HU is a Symphony II model and the wiring can be seen in the picture below : http://pictureposter.audiworld.com/66252/symphonyii_pin.jpg As you can see no sign of ignition live Quote Link to comment Share on other sites More sharing options...
merckx Posted September 16, 2010 Share Posted September 16, 2010 That should be easy enough to connect it to the fuse box, the current draw will be low so need to start uprating fuses etc if you connect it to the side of a fuse holder which is dead when you pull the fuse out. Extend the wire from the head unit if you need to, as long as the extended wire is the same the diameter or thicker (The wire core itself). You obviously to need to find a fuse in the fuse box which is live preferably when you have the key turned to the accessory position so you can use your head unit when parked up . I don't think the air conditioning fuse would be live unless the engine was running, unless your happy to just use the head unit when the engine is running of course. It's always useful to have a multi meter for identifying ignition live feeds etc , there should be one in the fuse box I would think. Quote Link to comment Share on other sites More sharing options...
jonathanc Posted September 16, 2010 Author Share Posted September 16, 2010 That should be easy enough to connect it to the fuse box, the current draw will be low so need to start uprating fuses etc if you connect it to the side of a fuse holder which is dead when you pull the fuse out. Extend the wire from the head unit if you need to, as long as the extended wire is the same the diameter or thicker (The wire core itself). You obviously to need to find a fuse in the fuse box which is live preferably when you have the key turned to the accessory position so you can use your head unit when parked up . I don't think the air conditioning fuse would be live unless the engine was running, unless your happy to just use the head unit when the engine is running of course. It's always useful to have a multi meter for identifying ignition live feeds etc , there should be one in the fuse box I would think. Didn't have enough time to poke around with the multimeter today I saw one unused slot but there's no feed going through it. The next best think I could find is the A/C (I figure even if I blow the A/C fuse I shouldn't worry too much - the rest are for ABS etc...) My A/C switches on even before turning the engine on. Yup, you gotta love Audis I've also found out the ciggy lighter stays on after even taking the keys out as I noticed my Nav wouldn't go out. However a mate mentioned its on a timer... pretty weird I would think. edit: I don't quite understand your first line mate. I thought I must connect to the side that's live after turning the ignition on? Did you mean I don't need to upgrade fuse if I connect to the dead side? Just doesn't make much sense to me since the dead side will always be dead? I should be connecting to the "live" side, meaning the side that gets 12V after switching on ignition I reckon? That side wouldn't be live anyway if the fuse blows. Unless I am thick and missed something? Quote Link to comment Share on other sites More sharing options...
Rob Posted September 17, 2010 Share Posted September 17, 2010 I know this doesn't help in anyway, but doesn't the A8 have a pretty damn awesome sound system as stock? Why change it? Quote Link to comment Share on other sites More sharing options...
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