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  • O.T. another auto electric question.

    I helped my friend install an aftermarket stereo in his car. After the install, the
    stereo would turn off and on during high load (volume)

    After much Googling the most common cause was an undersized power wire.

    Soooo ... I found a fat accessory wire going to the heating/AC fan and taped into
    this .. adding it to the supply to the stereo.

    The stereo stayed on .. BUT ... when you turn on the heater fan, the stereo shuts off.
    And it blows the fuse to the original stereo power lead.

    Is this some kind of loop back ground effect or something ? I am usually pretty good
    at this stuff .. but .. this has me a little stumped.

    I think taping into the access wire going to the fan was a normally accepted technique.

    Was it a problem leaving the original power lead hooked up also ?

    edit : I want to add that .. after the fuse blows in the original power lead, it effectively cut
    the wire making the tap into the fan the only power source. But it still shut the stereo off
    when the fan was turned on.
    Last edited by Mike Amick; 05-30-2016, 01:23 PM.
    John Titor, when are you.

  • #2
    Stop adding to circuits.

    Create a new circuit with a properly sized fuse and wire with one of these.
    Last edited by RancherBill; 05-30-2016, 02:39 PM.

    Comment


    • #3
      Run fat wiring directly from the battery and see if that solves your problem.

      Comment


      • #4
        Oh .. I feel confident that running a fatty from the Battery would solve it, but it needs to be
        an accessory wire so that the stereo shuts off when the car does.

        And that fuse tap in .. in the bomb. I am going to stop at the local stereo shop and see if they have
        one of those.


        Still don't know why the stereo shuts off the way I had it wired though.
        John Titor, when are you.

        Comment


        • #5
          What RancherBill said.

          When you add to circuits you are creating more problems because you are now overloading a circuit that cannot supply sufficient voltage and amperage to the stereo. The stereo system uses a lot of power when the volume goes up. Voltage and amperage requirements cannot be maintained on a circuit only designed for a specified load. As the voltage in that circuit goes down the amperage draw becomes greater, hence the blow fuses.

          Wire the stereo on an independent circuit using a fuse and wire gauge suitable for the intended load.

          If you want it to shut off with the key find a keyed source to use as a trigger circuit for a relay.
          Last edited by Willy; 05-30-2016, 01:55 PM.
          Home, down in the valley behind the Red Angus
          Bad Decisions Make Good Stories​

          Location: British Columbia

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          • #6
            Not enough info. Sounds like you butchered the wiring. Should have used an adapter harness. They are cheap most of the time and almost idiot proof.
            Some vehicles do not lend themselves to aftermarket head units as the factory system may have a hidden amp and/or vital circuits running through the factory unit.

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            • #7
              Fat wire from battery, fused AT the battery, relay switched by accessory power to supply stereo.
              Job Done!
              If you benefit from the Dunning-Kruger Effect you may not even know it ;-)

              Comment


              • #8
                It sounds like you are adding a radio with a very high power consumption. Very high. Fans also have a high draw, so when you combine both on the same circuit you are overloading it.

                The proper thing to do is to check the installation instructions to see how many amps it draws, and then add the recommended fuse and proper gage wire to the main fuse block.

                The phenomenon you observing is voltage drop. The voltage drops because the resistance in the wire is causing some of the energy to be wasted as heat. The amount of power wasted goes up as the amps increase.

                When I say main fuse block, I mean the one under the hood, where it has a large gage wire capable of handling a hundred amps or more. In many modern cars the fuse block under the dash often has a much smaller gage wire and is only expected to handle the electronics within the car.

                Have you considered buying him a headset? The same apparent sound for a lot less power AND it does not bother nearby people.

                Dan
                At the end of the project, there is a profound difference between spare parts and left over parts.

                Location: SF East Bay.

                Comment


                • #9
                  Originally posted by danlb View Post
                  Have you considered buying him a headset? The same apparent sound for a lot less power AND it does not bother nearby people.

                  Dan
                  Booh! Hiss!
                  Where's the fun in that, it won't annoy the neighbours or flap your trouser bottoms!
                  :-)
                  If you benefit from the Dunning-Kruger Effect you may not even know it ;-)

                  Comment


                  • #10
                    Originally posted by magicniner View Post
                    fat wire from battery, fused at the battery, relay switched by accessory power to supply stereo.
                    Job done!

                    This!

                    -D
                    DZER

                    Comment


                    • #11
                      Originally posted by Mike Amick View Post
                      Oh .. I feel confident that running a fatty from the Battery would solve it, but it needs to be
                      an accessory wire so that the stereo shuts off when the car does.
                      Use the original power feed to switch a relay on the new power feed. Also, be sure to fuse the new wire at the battery in case of a short.

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                      • #12
                        ok OK .. im getting the message.

                        I will add a tap at the battery ... and use the old switched power lead to a relay for accessory function.

                        I was aware of the voltage drop situation, I just never ran across it to this degree. These new
                        stereo's really draw some current !
                        John Titor, when are you.

                        Comment


                        • #13
                          Yeah, my Pioneer AVH4000NEX head unit wanted a 10amp power source, but it also has a bunch of USB plugin ports, a DVD drive and a 7" screen.

                          Had to search around for a bit to find a wiring harness that would work for it [as I'd rather not hack up my vehicle harness to connect everything up]. It made it much easier vs digging [or rigging up switches] to determine when the vehicle is in reverse and if the parking brake is enabled [no watching dvd's while driving... :-( ].

                          Comment


                          • #14
                            As others said spend $10 and get the correct wiring adapter pigtail. You will not need to cut a single wire in your car. The pigtail gets crimped to your head unit wiring and just plugs into the cars harness.

                            http://www.crutchfield.com/p_1207055...g-Harness.html

                            Comment


                            • #15
                              Also consider the ground return for the stereo's power. Older vehicles typically used the chassis for return connection, but that is not always reliable. Run an equal size ground wire back to the battery negative post.

                              Older car radios and stereos were limited by the 12V battery and 8 ohm speakers to about 8 watts (or 16 watts for 4 ohm speakers), and they were plenty loud enough to drown out the sounds of emergency sirens and also contribute to early deafness. Headphones can provide enough volume to make your ears bleed at 8 watts, and at least avoids creating an annoyance to the public. But they may be illegal.

                              http://blogs.findlaw.com/law_and_lif...eadphones.html
                              http://pauleschoen.com/pix/PM08_P76_P54.png
                              Paul , P S Technology, Inc. and MrTibbs
                              USA Maryland 21030

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