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putting 99 wiring on 2003 2500hd

Discussion in 'Truck & Equipment Repair' started by nqc2k, Dec 10, 2013.

  1. nqc2k

    nqc2k Junior Member
    from MA
    Messages: 3

    My first plow, so still learning a bit. I bought a MM1 off a 1999 chevy 2500 old body style with all wiring. Will these wires fit my 2003 2500HD with plow package? It isn't an ISO one, it has two relays on it. On the harness, i see 8275 written on it, and someone wrote 4676 in pen.

    It looks like it'll fit but I figured i'd check here before I blew something if it didn't. Here is a photo of my harness.

    Thank you.

  2. jrodgers

    jrodgers Senior Member
    Messages: 156

    Not sure but I know when I went from a 01 to an 05 the wiring for the lights was a little different.
  3. GONZO911

    GONZO911 Member
    Messages: 41

    wiring for plow

    From what you supplied for truck information, harness should work....if the headlights are the hb3/hb4 style-two separate bulbs for high and low beam. The 1999 might have single headlamp, then harness would be different. Main difference in the newer one would be the head light plugs that plug onto headlight bulbs. harness number is 28800-1. Should be tag on the harness that would have number on it.
  4. alohazabel

    alohazabel Member
    Messages: 44

    you'll need more relays, different lighting harness

    You'll need a different harness for the lights, and either 2 or 4 more relays I think depending on whether you want to wire up the daytime running lights or not. It can be tough to find the parts because all the dealers will try to upgrade you to an isolation module type system.

    I did this with a half ton. I went from old body style '99 to '01, and I was told that even though the plugs fit the lights, that it wouldn't work because the switching is opposite. I looked all over on EBAY and local dealers for the wiring harness, but ended up finding the parts at:


    I called them and the guy I talked to knew exactly how to do this and what wiring I needed.
  5. nqc2k

    nqc2k Junior Member
    from MA
    Messages: 3

    Plugged it all in last night, and the right marker light is on for the plow...that's it, everything else is dead.

    If I jump over the solenoid, it makes a sound like the plow is trying to raise, but I think it may be raised all the way up.

    Joystick light is on, but no response. If I joysick down, light turns off.

    Plow supposedly work great last winter.

    Even if lights don't work, plow controls should right?
  6. nqc2k

    nqc2k Junior Member
    from MA
    Messages: 3

    Looks like I was missing a ground wire to my solenoid, plow works fine now. As far as lights, it would seem I will end up wiring new lights onto the plow and hard wiring them in with a switch on the dash.

    Thanks again.
  7. alohazabel

    alohazabel Member
    Messages: 44

    switched power???

    I'm working on a similar setup.

    what wire (or fuse) did you use for the switched power for the plow?
    and where is it located?


    p.s. good idea to just hard wire new lights with a switch. alot easier and cheaper than wiring up all those relays and buying a new headlight harness
  8. mpriester

    mpriester Senior Member
    Messages: 424

    when wiring the plow lights be sure to use a relay so as not to overload the switch. this is how i wired mine and it works great.