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Fisher Truck Swap 2002 Sierra to 2005 Yukon.. Headlight Wiring

Discussion in 'Residential Snow Removal' started by Horvath2015, Oct 28, 2015.

  1. Horvath2015

    Horvath2015 Junior Member
    Messages: 19

    Wonder if you could help with this issue...

    I installed everything from the 2002 Sierra into the 2005 Yukon... When I hook up the light wiring harnesses and turn the lights on all 4 headlights on the Yukon light up.. Meaning both low beam.. and both High beam at the same time.... It doesn't change when I hit the dimmer switch.

    Kind Regards
  2. bassboat

    bassboat Junior Member
    Messages: 3

    Did you solve this? I'm going through a similar situation: moving a MM1 from a 2001 Silverado to a 2003. My understanding is that GMC was nice enough to change the polarity on the headlight circuit in the HB3/HB4 after 2002.
  3. pyro29

    pyro29 Member
    Messages: 38

    Check the commons. On the HB3/HB4, the truck side connectors can be "flipped". Make sure whatever wire is common is on the correct side going into the module.

    If you're running a 4 port module, the common will be the dark blue wire and if you're running a 3 port module, the common wire will be labeled "COM". With a 4 port module, also check to make sure your configuration plug is of the correct orientation.

    On the truck's factory pigtails, the common wire is typically the darker color of the two leads to each lamp, but always double check that using a test light.
  4. Horvath2015

    Horvath2015 Junior Member
    Messages: 19


    I never did figure it out.. I just used the low beans on the harness and left the high beams plugged into the truck not using them in the plow harness and set up.

    Looking what pyro29 and you said, I am going to double check everything. Sounds like it maybe as simple as switching the two wires around on the plow side headlite plugs? As long as them commons match up.

    Thanks Eric
  5. Horvath2015

    Horvath2015 Junior Member
    Messages: 19

    FIXED... Reversing the truck head lite plugs into the plow harness fixed the issue..(Hooking them up backwards)
  6. bassboat

    bassboat Junior Member
    Messages: 3

    I sorted mine out too. Got a terminal punch tool and reversed the Fisher harness where it plugs into the factory headlight connectors - 8 wires, 20 minutes:mechanic: