HELP Fix accessory power

Discussion in 'The Projects Forum' started by acglass, Jan 21, 2013.

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  1. acglass

    Thread Starter New Member

    Jan 21, 2013
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    I'm replacing the aftermarket in dash car stereo in my Chevy class C motorhome. I thought it would be straight forward, but the p.o. put a chrome push button in the circuit. Then, it would seem, another p.o. cut the wires to the button and, as of now, it's not functioning. Further, the stereo functions with the key on, but not with it in the "accessory" position. So I have a non functioning button as well as a non functioning accessory key position. (I'm not sure what else powers in ACC, but the gauges don't move).

    <Can't figure out how to upload photos>.

    It seems the intent of the button may have been to easily power off the radio during storage to eliminate battery drain. If so, this makes sense and I would like it to function again. I also would like the accessory function restored.

    Here's the layout...
    There are two attachment points or "posts" on the back side of the button. (It's a simple push button. Push click, push click.) One side carries blue wire, the other orange.

    On the orange post, three wires are connected... The first is attached to a single blade of a flat two blade fuse and plugged into the fuse block "pwr" space. It exits with a good inline 20 amp fuse and attaches to the buttons 'orange post'. Two orange wires exit this post. One goes to the stereo accessory wire (not working) and the other is cut. (It may be worth noting that there is a cut piece of orange wire taped onto the blue wire on it's way to the battery just inside the pass through hole in the firewall.)

    On the blue post there are two wires... The first is connected from the battery (via an attached post) to the 'blue post'. The second exits and goes up to the stereo, but is not attached to the yellow power wire. It too is cut.

    The black ground wire is connected to the stereo then looped and taped to the wires of each button post before being grounded to the metal body.

    The current stereo power wire (yellow) is not routed through this button, but is direct wired to another "pwr" port on the fuse block.

    Please help me understand this button and let me know where to reattach the cut wires to make everything function properly.

    Thank you.
     
  2. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    I cannot see your photo. Try uploading it as an attachment.

    Doesn't the RV have a deep cycle battery for accessories, and only use the starter battery for starting via a battery isolator?
     
  3. acglass

    Thread Starter New Member

    Jan 21, 2013
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    This is the head unit in the van area. I hesitated putting motor home in the post due to the confusion it would 'no doubt' cause. The deep cycle is for the coach accessories. This is in the cab and attached to the cab battery. It's essentially installing a stereo into a Chevy van. Photos are attached to help with describing the problem and layout.

    I do not know what these things are in my hand or why they are necessary.
     
  4. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    The two items in clear heat shrink are diodes, which can isolate batteries at the cost of a small voltage drop.

    It looks like the orange wire is going to continual power, and the switch will turn that off/on, the source of the power is likely the battery with the higher voltage after the diodes, or a similar scheme.

    If you have a DMM, you can check the voltages to see if the orange wire is plugged into full time power or ACC power, as well as which battery by disconnecting one battery and measuring, reconnecting, and disconnecting the other.

    Without tracing the full path of the wires, I can't make more of a guess than that.

    The silver box with the two wires (orange/blue) is too blurry to tell what it is. Looks similar to a blinker or bi-metal fuse.
     
  5. acglass

    Thread Starter New Member

    Jan 21, 2013
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    The dictionary says a diode restricts current flow to one direction. If all the current flow is from power to the stereo, then why would a diode be necessary?

    The silver box is the back side of the button (sorry for the blurred image).

    The path of the wires is traced via my description; sorry if it's confusing.

    I still can't make out where the cut orange wire should be reattached.

    Thanks.
     
  6. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    On the stereo, the yellow wire needs constant power to save the settings.

    The red wire is what needs power for the radio to turn on and work.

    Untape the other orange cut wire and see if the length matches to the distance needed to get to the switch.

    There should be an outlet with a label like "ACC" (Accessory) on the fuse box, and that is where the red wire should go. Right now, it is probably in an "IGN" (Ignition) power tap. The owners manual may help you find and identify those.

    It is also possible that the stereo connected to the stock radio connector via an adapter, so look for that, or any of the blue plastic "Crimp taps" that allows one to tap a wire into another without cutting it. They are very common in RV applications, you pinch down a metal tab with a pliers when one side is over the wire to be tapped, and the wire you are feeding to is pushed in halfway. Once it is pushed down, there is a blue cap that flips over to insulate the tab from being shorted.

    Find out the destination of the blue wire, and any orange wire that passed through the wall, and with the information above, you should be able to figure it out.

    I'd suggest fixing it PROPERLY to avoid a fire, many RVs catch on fire from poor DIY wiring additions, so be sure that any wires connected to power have a fuse within the first 6" of where they are connected to power.

    If you are unable to figure this out, I'd suggest taking it to a car audio shop, they tend to be experts in power routing in any sort of 12V vehicle, such as an RV. A Digital Multimeter/DMM is almost required to find the right connecting points, a cheap $10 one from radio shack will do, search the web for "using a DMM" to learn how to operate it (it's VERY simple).
     
  7. Georacer

    Moderator

    Nov 25, 2009
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