_ethrty-Andy_ 2132 Report post Posted July 20, 2012 so car works fine as does the stereo etc etc. put in wiring for an amp and sub into the boot. ive wired up a sub and amp many times before, but this time i have an issue, which cant be the wiring so im stumped. amp and sub do not work. across the amp im getting 12.4V or so when the car is 100% off, and 0V across the remote to negative terminal. sweet BUT when the car is in ACC or ON mode, the voltage drops/rises to 4.6V 4.7V across both above mentioned points, untill i turn the car back off. Okay so i thought the amp might be stuffed, maybe the voltage regulator in it. It was a Sony 350W 2/1 channel i brought maybe 5 years ago, and havent used it for 2 or so. So i swap in a Kenwood 4/3 channel i KNOW works because it was working in the Mercedes before i pulled it out on Tuesday. Exact same results except the voltage is 8.xV instead of 4.6-4.7V. swapped the Sony back in and back to 4.6V. Anyone have any ideas? Quote Share this post Link to post Share on other sites
BM WORLD 1283 Report post Posted July 20, 2012 just try jumping the 12v positive across to the remote wire on teh amp with out using your blue wire from the head unit. see if that works , check your earth and positive supply is a good one , nice tight conections and not sitting on paint etc Quote Share this post Link to post Share on other sites
_ethrty-Andy_ 2132 Report post Posted July 20, 2012 yep all my connections are good. changed my grounding point in the boot, and then redid the fuse holder incase they were dodgy, but seem fine. reckon its safe to go from 12V to the remote? i thought about that but im hesitant to as the remote is only a signal wire, next to no current is supposed to be able to go into it from my understanding. amp might be 5 years old but dont really want to blow her up ha. would indicate if its the headunit to blame though wouldnt it... Quote Share this post Link to post Share on other sites
polley 916 Report post Posted July 20, 2012 connecting the remote to the 12v is fine. Quote Share this post Link to post Share on other sites
Neal 544 Report post Posted July 20, 2012 (edited) + ONE. AMP Power one relays will be fine from 10 - 16 volts across the remote terminal. More recent (1999 +) amps have voltage sensors so will not power up below 11 volts (to protect amp PSU and to allow enough charge in battery to start car). You'll need to check in more detail why the HU is dropping voltage when switched to ACC etc Things to check 1, ACC connection getting partial ground through wiring 2, Power anttennia output is not going to ground 3, HU speaker outs arn'te going to ground ( causing over current and dropping remote output voltage) 4, HU chassis has proper ground 5, ACC connection from car when turned on is at same voltage as measured across battery terminals (if this is low then these is where your issue is coming from HU, double check all HU wiring) Edited July 20, 2012 by Neal Quote Share this post Link to post Share on other sites
_ethrty-Andy_ 2132 Report post Posted July 21, 2012 hmm supply is definately ok. its connected to the battery which is a strong unit. I havent been using the car much lately while i had the mercedes and i could go for a week ago without starting it and it would fire up first time every time. Its GOT to be a grounding issue i think. I havent put it to the usual place i choose on E30s i will do this this afternoon and see what happenes. i cant understand while its the normal 12.4V when the car is off though, 12.4V all the time or 4.6V all the time is much easier to diagnose! Quote Share this post Link to post Share on other sites
polley 916 Report post Posted July 21, 2012 This should take you no longer than 30 mins to sort out. .. it's 3 wires. Remove the remote wire and connect it directly to +12v, this removes the headunit from the picture (even though it sounds like its not the issue anyway). Get your volt meter out and measure the voltage drop on your earth and +12v connections, this will tell you what wire / connection is giving you trouble. Fix the offending wire. Enjoy your skrillex. Quote Share this post Link to post Share on other sites
_ethrty-Andy_ 2132 Report post Posted July 22, 2012 This should take you no longer than 30 mins to sort out. .. it's 3 wires. Remove the remote wire and connect it directly to +12v, this removes the headunit from the picture (even though it sounds like its not the issue anyway). Get your volt meter out and measure the voltage drop on your earth and +12v connections, this will tell you what wire / connection is giving you trouble. Fix the offending wire. Enjoy your skrillex. correct. was playing around this afternoon on it. decided it HAS to be the ground cable as its the common wire. grounded else where, wire brushed etc. then decided to get rid of it and put a new negative cable in to the same grounding point and it works fine now. I suspect the neg cable i had was oxidised or otherwise and was faulty, it has been sitting in the shed for a few moons in a bag of various audio cables, mind you same as the one i swapped in. Bass drop whaaatttt Quote Share this post Link to post Share on other sites
