Problems after installing lmc headlight harness

[Plunkett]

I installed lmc's he headlight harness in my 87 gmc sierra yesterday. I used the diamond style headlights from classic industries with h4 bulbs that came with them. I plugged the harness in just like it was labeled. The problem is that when I turn on my headlights all 4 lights come on and the high beams are on high and the low are on low. I can switch the plugs around and the low beams will shine bright. Does anyone have any tips to help me out?

[Mikepannell]

If you bought the one that came in the yellow packaging with china writing.. You will have to make sure your ground and low beam wires are correct.. I had to switch mine on both side and everything worked..

[piecesparts]

The whole problem is in the wiring that is in the actual headlight plugs or maybe the plug that plugs into the factory headlight plug, on the harness. This will take some time and a electrical power probe to figure out. First, look at your factory headlight plugs and use the probe to see which one is powered when the headlights are on in a low beam pattern and then in a high beam pattern. Now Second, Take a look at your new bulbs and see which terminal on them is the high beam and the low beam. Use jumper wires and a battery to test this out. It is easy to do and when you know what is high and low, then go to the next step. Finally, connect the harness to the factory light harness and turn the headlight switch on without any bulbs connected to the harness and check to see what wires are powered in the plugs with the headlights in low beam and then high beam. My bet is that you will have to pull some terminals out of the plugs and put them into other holes in that plug to reverse the light patterns. (The terminals will come out if you use a small probe to depress the clip on them and then reset the clip before inserting in the next terminal hole) I purchased a wiring harness form another outlet and that is what I had to do when I wired up my new headlights. My stuff was not from LMC, but many outlets sell the same items under their part numbers. I finally got everything to work out right.

Take your time and think it out if it seems to not work right. If I remember right I had to revers two wires in the plug that went to the factory harness and then I had to move tow wires in each plug to get the ground and power circuits aligned properly. I had my truck torn apart for about a whole day trying to figure out what needed to be changed.