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truck reverse wire question

Discussion in 'Truck & Equipment Repair' started by badbowtie, Dec 2, 2013.

  1. badbowtie

    badbowtie Senior Member
    Messages: 106

    I have a 99 chevy k3500 old body style that I mounted two 35 watt rear lights under bumper for backing up and or just plowing/salting. I wired the lights up with a relay in the rear of the reverse lights at the signal to turn relay on and off. So right know they work great when I ship truck to reverse. But I also want to figure out were that wire is up under the dash so I can wire a switch and send power to that wire when I want to flip the switch so I can use while driving forward also. I would like to just tie in right under the dash but not sure color and location or if I have to I guess color on the PRNDL module on side of trans.
    Thanks
     
  2. 07PSDCREW

    07PSDCREW Senior Member
    Messages: 863

    I did the same that you wish to do. But you have to change how you have it set up. I assume since you have a 3500 that you would have an rv plug in back. If so, the center pin should be reverse lights. I wired my add on lights to ground and supplied power from that wire that's in the center pin of the plug. (Black with green stripe???).
    Then under the dash find the relay that clicks when put into reverse. With the relay out, Use a probe to find the leg of the relay that shows ground when shifting into reverse. Get a fuse tap and slide it onto that relay leg. Then take a wire from ground to a switch, then to that fuse tap. You will then have all rev lights when shifting into rev and be able to toggle them on whenever you want using a factory circuit with no wires run to the back. I made my own thread on it with diagrams. Ill try to find it and then post it. It's on a ford but it should be the same.
     
  3. 07PSDCREW

    07PSDCREW Senior Member
    Messages: 863

  4. badbowtie

    badbowtie Senior Member
    Messages: 106

    Okay I was not aware there was a relay under the dash for reverse lights I guess I will check that in the morning but if there is I should be able to maybe leave my back alone and wire a toggle switch to energize 86 on the relay and that should let them work on toggle or while in reverse. Let me know if you find your diagram. I bet there is a wire under the dash some where on here that I can send the hot to to turn on the lights just not sure where.
     
  5. 07PSDCREW

    07PSDCREW Senior Member
    Messages: 863

    I posted the thread above and just below my first reply. There should be a reverse light relay either under the dash or under the hood. I'm not too familiar with GM. The reason I suggest using the hitch wiring is because it is a higher amp circuit than the regular reverse circuit.
     
  6. badbowtie

    badbowtie Senior Member
    Messages: 106

    I am using the hitch wiring I am using a relay and I am using the 12v constant wire in hitch plug for my 30 on relay and using 85 as ground and using 87 on relay for both new lights and 86 goes to factory reverse lights. So all the load is not on the little oem back up wire just using it to turn relay on.
     
    Last edited: Dec 3, 2013
  7. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,971

    Is your tk an old body style or new? That's gunna make a huge difference
     
  8. badbowtie

    badbowtie Senior Member
    Messages: 106

    It is old since it is a 1 ton.
     
  9. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,971

    I'm pretty sure there's no relay for the reverse circuit
    You may have the pins mixed up on the relay tho. Doesn't seem right
     
  10. badbowtie

    badbowtie Senior Member
    Messages: 106

    yea I looked and no relay under dash for reverse but wire has to be here some where. Relay I believe is correct.
    30 power
    87 lights (new lights)
    85 ground
    86 signal wire (reverse wire)
     
  11. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,971

    Reverse wire is on the trans switch.
    I'll look at wiring for the relay later on
     
  12. Whiffyspark

    Whiffyspark 2000 Club Member
    from SOMD
    Messages: 2,402

    What Youre trying to do is have the lights come on in reverse but also be able to control them manually, correct?
     
  13. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,971

    If you want manual on/off just leave the reverse side out on it and just go with the switch.
    The relay wiring is good. Didn't seem right till I looked at a relay
     
  14. badbowtie

    badbowtie Senior Member
    Messages: 106

    Yes lights come on know while truck is in reverse. I also want to be able to manually flip switch and make them come on also. I figured I was going to have to go to trans you have a wiring diagram to confirm which wire it is down on trans.
     
  15. dieselss

    dieselss PlowSite Fanatic
    Messages: 10,971

    Ok. But why all the extra work. Just switch them and not worry bout the rev wire
     
  16. Whiffyspark

    Whiffyspark 2000 Club Member
    from SOMD
    Messages: 2,402

    I've done this on my truck. I just ran a while from the ground of the lights to the cab and put a switch on the ground side

    I split the ground wire. Grounded one side ran other side to cab. Same for power I think. One for reverse one for constant 12
     
    Last edited: Dec 3, 2013
  17. badbowtie

    badbowtie Senior Member
    Messages: 106

    Well for a update I wired the lights in at the rear using power and signal from 7 way and a relay. I also tapped into the lt green pin f on the PRNDL switch on trans and ran it up into dash and a power wire to a switch. So I can flip switch on and make spot lights and backup lights come on. Or when I shift to reverse they come on. I did use them this weekend plowing and salting and they worked great.
     
  18. 07PSDCREW

    07PSDCREW Senior Member
    Messages: 863

    Good job!Thumbs Up