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Electrical Work.

Discussion in 'GM Electrical Tech' started by Conlan Rose, Dec 21, 2012.

  1. Conlan Rose

    Conlan Rose Active Member 2 Years 1000 Posts

    Ok, today I spent many hours working on the truck fixing some wiring I messed up. Well it is all good now, but I need some diodes to protect the system from backward feeding power. Does any one know what I should use?

    I'm protecting my back up light from back feeding in to the reverse circuit and the reverse lights. The light is a 55w utility light, that is activated either by the reverse circuit via a relay or by a switch on the dash. I need to make sure that when the switch is activated it doesn't back feed to the reverse circuit.

    Other work I did today was install new bulbs in the climate controls 2012-12-21_19-00-19_489.jpg
  2. dpeter

    dpeter Rockstar 4 Years 500 Posts

    If you go the relay route activated by the reverse/backup lights then no problems. If your back-up lights are activated by a switch on the transmision or the shift lever then you should have no problems with any back feeding issues when using a seperate switch. If activated by the body control module then maybe a blocking diode would be wise but not sure it would be neccessary. The only thing in my wiring diagram(99-06) is the automatic mirror adjust that would be activated by putting power to the back-up lamps.
  3. Jamm3r

    Jamm3r Member 1 Year 100 Posts


    The relay should do the job for you if you have it wired correctly, no diode required.

  4. Conlan Rose

    Conlan Rose Active Member 2 Years 1000 Posts

    So you are saying I should not have a problem because the relay is protecting the reverse circuit.
  5. Jamm3r

    Jamm3r Member 1 Year 100 Posts

    Yep. Unless you wired the switch to the relay coil, instead of in parallel with the contacts. In that case you need two relays. It's no big deal -- if you have a problem you'll see the reverse lights come on with the work lights when you use the switch, no damage done, just a nuisance problem.
  6. Conlan Rose

    Conlan Rose Active Member 2 Years 1000 Posts

    I was just looking for confirmation before I finished the wiring tomorrow. All I need to do is wire the switch to the light. Currently the light is only controlled my the reverse circuit.

    - - - Updated - - -

    Where does the orange wire for the trailer harness go to get power? I cant find it on any wiring diagrams, and there's about 20 orange wires that run to the dash and fuse box.
  7. SurrealOne

    SurrealOne Former Member ROTM Winner 1000 Posts

    I'd use a diode as you had originally intended. When I install my Dually D2's to have a relay that's triggered by either the reverse circuit or a toggle switch I'll be using a diode-approach similar to this (which has a Radio Shack part number for you, if you like):
  8. Conlan Rose

    Conlan Rose Active Member 2 Years 1000 Posts

    Ok sounds good.
    Here is a diagram of how it will be wired, the switch is rated for 20 amps which is far more then it ever will deal with.
    back up light wiring diagram.jpg
  9. Jamm3r

    Jamm3r Member 1 Year 100 Posts

    Typically to the "aux power 1" stud on the fuse block although it may just end in a ring terminal somewhere in the vicinity of the fuse block and not be hooked up to anything. I believe they left the factory that way and the dealer hooked them up, or not, at their discretion.

    - - - Updated - - -

    :: shrug ::

    That will work. The diode doesn't accomplish anything though, in this situation.
  10. Conlan Rose

    Conlan Rose Active Member 2 Years 1000 Posts

    I may be going with a different relay set up where it actually does something. I will run both the switch and the reverse circuit to the 86 terminal with both the switch and circuit protected by a diode. The switch will draw power from the aux fuse box under the hood.

    - - - Updated - - -

    It is not attached to the aux power one terminal and I have not found a ring terminal any where near the fuse box. I have found a female connector of some kind that just juts out of the wire loom. Could that be it? I can't tell the color of the wire.

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