RCA Current leak post amp /headunit install..? | FerrariChat
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RCA Current leak post amp /headunit install..?

Discussion in '348/355' started by lemon355, Apr 6, 2024.

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  1. lemon355

    lemon355 Karting

    Aug 8, 2009
    218
    Melbourne Australia
    Full Name:
    Peter Kay
    #1 lemon355, Apr 6, 2024
    I recently had a headunit and 4 channel DSP amplifier installed in the vehicle.
    All was working well when I picked it up at the shop but when I got home I was shocked to find that when I turn the battery isolator switch off the door jam lights still stay on, and the instrument cluster lights up when the key turns.

    In fact the current leak is so bad that there is enough current to cause he car to (click click click) like a flat battery when you attempt to crank the car!!


    In order to isolate the source of the leak I took everything out of the system such that the only connections I was left with were the following and there was no current leak with the isolator off.

    Headunit RSX GS9
    MAIN HARNESS "A": YELLOW 12V+ & BLACK GND ( Both direct to Battery)
    ACCESSORY HARNESS "B"
    Red ( ACC switched power.. not constant as per OEM)
    Blue /white stripe: remote amp turn on and antenna booster combined
    Orange Illumination (borrowed from radio bezel guages)


    Amplifier MOSCONI DSP /AMPLIFIER 4 x 100W RMS 12V+ direct to battery) and ground to the chassis end of the cable that passes from the OEM isolator switch to the chassis bolt just behind the drivers headlight

    I then added the RCA's.. The addition of only one RCA produced a VERY FAINT glow in the door jam lights when the isolator was off, but the Instrument cluster did not illuminate when the key was turned.
    Successive addition of the the other x3 RCA gradually increased the current leak, till the dash lit up on key turn, and the car tried to start on cranking but would only go click click click like a flat battery as the current is obviously not enough.

    When I added cheaper RCAS. the problem was much worse., as they aren't insulated as good.
    Such that x2 cheap RCAS was equivalent to the current leak of my x4 good RCAS

    NB: During this testing the amplifier was Isolated and not touching the chassis except via the ground cable.

    I'm pretty stumped and looking for help, as the current leak is pretty bad and the equipment is quite expensive. ( but everything is fuse protected)

    Should I disconnect the HU ground from the battery and put it in the same place as the amplifier ground?
    Should I re-locate the HU power from direct to battery to the OEM radio harness power wire..?
    I know RCA's do carry current, but should they carry this much..? and where is the power coming from and what is it looping through..?

    The stereo and amplifier work

    Any help is much appreciated as its starting to scare me a bit now..:eek: Image Unavailable, Please Login
     
  2. m.stojanovic

    m.stojanovic F1 Rookie
    Silver Subscribed

    Dec 22, 2011
    3,212
    Serbia - Niš
    Full Name:
    Miroljub Stojanovic
    #2 m.stojanovic, Apr 6, 2024
    First: DO NOT try to crank the engine or switch on any bigger consumers (headlights, heater blower etc.) while the battery cut-off switch is off because you may smoke your RCAs or their jacks may get "welded" inside the sockets.

    Connecting the ground of HU to one side of the battery cut-off switch and the ground of the AMP to the other has established a ground path, via the shields of the RCA cables, bridging the isolation switch, as shown on the drawing below. You should connect grounds of both, the HU and the AMP, to one side of the isolation switch. If you connect both to the battery side of the switch, the switch will not isolate them from the battery and they may cause certain battery drain so it is better to also connect the ground of the HU to the chassis side of the cut-off switch.
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    johnk... and lemon355 like this.
  3. lemon355

    lemon355 Karting

    Aug 8, 2009
    218
    Melbourne Australia
    Full Name:
    Peter Kay
    #3 lemon355, Apr 6, 2024
    Outstanding!!.. That explains things perfectly.

    I had no idea that the installer had not checked this when I picked up the car.
    I have played the system pretty loud about 3 to 4 times and with no issue.and always with the isolator switch on, never off.
    But today I decided to work on the vehicle so I turned the isolator switch off..

    I then proceeded to put the door trims back on,

    When I finished my work, I turned the key expecting to have no power, but the instrument cluster lights then went on.
    I got confused at that point thinking that i had inadvertantly turned the isolator switch ON instead of OFF.

    So I tried to crank it and it just went click click click (like the battery was flat)

    Anyway there seems to be no damage done as the HU and Amplifier still work perfectly.. so I was lucky on that one.;)

    Again many thanks for taking the time to clarify the solution, and recoding it in the annals of Fchat history for future reference..:)
     

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