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Suspension causing beeping to come through my speakers? HELP

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  • Suspension causing beeping to come through my speakers? HELP

    Hi guys, This is my first post here. I have completed an install of a laptop mounted in my boot and a xenarc monitor in the dash... as well as a few other things along the way. It all connects up and runs, but I have found I am picking up some weird beeping noises through my speakers.

    I have two modes for my suspension sports and automatic. When on sports (but not in automatic), I think it must do real time adjusting on the suspension, cos I can hear little chirping sounds when I listen right up to it and move the car. These chirping sounds are in time with the beeping coming through my stereo, so it is somehow picking up some noise from that.

    My laptop is connected to my head unit with a cable going from rca line in on the head unit to headphone line out on the laptop. The laptop is connected to the battery directly (via a relay to turn it on when key in ignition) with a 12V power supply (minus the cigarette plug) and then grounded.

    I found that when I diconnected the lead to the battery (ie no power to laptop) it beeped even when not on, as long as the ground wire was connected. If I disconnected that the beepng stopped. This was with no other plugs connected into the laptop, apart from the one to the head unit. Took that ground out as well, and connected up monitor cable only, to the laptop. Beeping came back. Took it out beeping stopped. Ran a wire directly from the back metal planel where all the plugs go into, straight to my grounding point and the beeping came back.

    My grounding points for the laptop and head unit are clean and connected to freshly sanded, bare metal on the body of the car. I have run a cable between the two points to stop any problems from using different grounding points. Hasn't helped stop the beeps.

    The original cable between laptop and head unit was down the side of the car. I changed cables and ran the new one through the centre of the car in mid air about halfway up, so that it was not near anything that might induce noise in the cable. Still didn't help beeps.

    I would really appreciate any help on finding the cause of the beeps so that I can get rid of them and have a completed system. Please let me know if you have any ideas, its starting to drive me crazy...

  • #2
    interesting - the only thing I can think of off the top of my head is to check all grounds and make sure your signal cables aren't run next to any power cables...but you've already tried all of that.

    otherwise, I'm going to subscribe so I can see what other people have to say...lol
    Jan Bennett
    FS: VW MKIV Bezel for 8" Lilliput - 95% Finished

    Please post on the forums! Chances are, someone else has or will have the same questions as you!

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    • #3
      is this by chance a newer bmw? I have a friend who installed a system in his new 745li only to have it REALLY screw with the electronics, no matter what he did he couldn't solve the problems... the car was at the bmw dealership for months... he got it back witrh everything disconnected.... the dealerships official advice was that this system couldn't be installed in this car.... they charged him a fourtune & gave him back a big mess.... a lot of money down the drain....

      not saying this is your situation at all, just curios if it's a bmw....
      MY NEWEST INSTALL:modded infiniti fx with big screen

      first windows carpc install........my liquid cooled LVDS screen :D

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      • #4
        Originally posted by bnew019
        I have two modes for my suspension sports and automatic. When on sports (but not in automatic), I think it must do real time adjusting on the suspension, cos I can hear little chirping sounds when I listen right up to it and move the car. These chirping sounds are in time with the beeping coming through my stereo, so it is somehow picking up some noise from that.
        Just to clear this up. you can hear this chirping where?

        1. Hifi speakers with no laptop connected
        2. Hifi speakers with laptop connected and on
        3. Not through the hifi but from the car generally.

        Originally posted by bnew019
        I found that when I diconnected the lead to the battery (ie no power to laptop) it beeped even when not on, as long as the ground wire was connected. If I disconnected that the beepng stopped. This was with no other plugs connected into the laptop, apart from the one to the head unit. Took that ground out as well, and connected up monitor cable only, to the laptop. Beeping came back. Took it out beeping stopped. Ran a wire directly from the back metal planel where all the plugs go into, straight to my grounding point and the beeping came back.
        1. No 12V to laptop but ground connected = beep (T/F)
        2. No 12V and no GND = No beep (T/F)

        3. Connect Monitor to laptop but no 12V or gnd to laptop = beep (T/F)


        was the laptop connected to the HU during all the above 3?


        If the above 3 (T/F) are all True, then it definitely sounds like the noise is coming from the ground. (The laptop will be grounding through the monitors ground in 3)

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        • #5
          ok I have a car with electronic suspension control, and that buzzes like buggery on the HU if tuned to am.

          All cars like mine (citroen xm or later) do, we just use FM!
          Lez, more widely known as flez1966

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          • #6
            Um I wish I could say I could afford a new BMW, but sadly no. My car is a Nissan Cefiro... Not sure if you guys have any of those over in the US...

            To clear this up... I can hear the 'chirping' when I open the bonnet and put my ear close to the top of the front suspension on either side. It is very quiet, and the best way to describe it is a whirring/chirping sound, a bit like crickets or cicadas. I think this is just the servo or stepper motors or whatever is in there. The 'beeping' is the sound that is being picked up and coming through all the speakers mounted in the car (not the laptop ones, I disconnected those before I mounted the laptop in the boot), and is in time exactly with the 'chirping' sound.

            Enforcer, yes it is true to all the 3 things you said, and yes the laptop was always connected up the HU for them. I tried another test last night, also thinking it was the ground, and agree that there was likely a ground through the monitor when I plugged that cable into the laptop. I found the old power adaptor for the wall for my laptop and plugged it into the laptop. I then ran it around the outside of the car, and up to the battery. I touched the ground pin of the plug that goes into the wall, to the negative on the battery, and the beeping came back.

            I am not sure exactly what this shows, but guess it means the beeping is not being picked up through the ground point used by the laptop. Possibly being picked up by the HU ground?

            I have an rca line in on the back of the HU, and a head phone AUX in on the face plate of the HU. Beeping was occurring when plugged into the line in on the HU, then pulled those cables out, used a 2-rca-to-headphone adaptor, and plugged that into the aux in on the face plate and beeping stopped. Are these two inputs on the HU somehow different? and does this help diagnose the problem?

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            • #7
              well if it beeps when connect via the line in (rear rca) but not when connected to the aux in (front 3.5mm) then I would say the the front has some form of isolator built in, but you cant drive around like that!

              are the rear rca mounted on metal or plastic, do you get beeps f you ground the hu case to the ground.

              what happens with a ground wire touched on the rear rca 'outer' metal?
              Lez, more widely known as flez1966

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              • #8
                Not sure what you mean about mounted on metal or plastic... The HU unit has two short cables with female rca sockets at the end. The cable from the laptop has two male rca plugs at the end. I have tried two of these cables. One had a metal casing around the rca plug, and the other plastic.

                I will try and run a cable from the ground for my HU to the metal outer body of the HU, and then try it on the ground 'outer' of the rca? Will try that tonight and let you know what happens....

                Thanks for the ideas....

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                • #9
                  I tried to ground both the cable, and the body of the HU. Neither made any difference. However when playing around behind the HU I discovered that the cable still run down the side of the car caused beeps even when not plugged into the laptop. The beeps weren't as loud as when it was plugged into the laptop, or if i touched the headphone plug on the end to the ground point for the laptop directly, but were still there.

                  I played around behind the HU and found that the beeps would come and go in volume by moving around the rca plugs. Also the plugs on the end of the cable down the side of the car were the metal ones. When I separated the metal ends the beeping was reduced further, and when I touched the metal back together the beeping increased.

                  I am not really sure what this all shows, but the other cable I am using has plastic around the rca plugs, so there are no metal parts to touch on them. There are no beeps from this cable when not plugged into the laptop. Possibly this cable is better insulated than the other?

                  It all sounds a bit like the cables are picking up some sorta induced noise from somewhere in the car, and possibly the laptop (through the ground somehow). However this does not seem to be the case because the noise does not exist when plugged into the auxillary input on the front of the HU. Whatever the auxillary is doing differently to the line in, I somehow need to replicate on the line in?

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                  • #10
                    I think the aux on the front has some sort of ground loop isolator built in, possibly to prevent damage from odd voltages that may get in from bad external devices.

                    Head units, should be called head aches lol
                    Lez, more widely known as flez1966

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