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Discussion Starter #1
Hey guys I'm new here. I've learned a lot from this forum over the years so I figured I'd join. I bought a 1993 gmc sierra and an old mm1 fisher. The electronics I bought separately because the price was right. I got the mounts and all the harness for 250 bucks. I just installed everything minus the plow today and I've got both low beams on the truck. On high beam, my lg beam lights up but my passenger side low and high beams come on at a glow at best, while on high beam!.........disclaimer, the harnesses came off a 90 gmc w/t with single sealed beams, I have the poly capsules on mine. I modified the harness to save a few hundred bucks. I MAY have goofed up, BUT, I've made alit of harnesses and I'm pretty savvy with that stuff. I figured I'd ask if anyone else has had this issue. I tried to play with the configuration plug(4port module) and all I did was go from both lows on low to only LH low on low. any insight help or experience is much appreciated!!
 

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what I have told guys in the past running old stuff, trying to save a few bucks. Just run a toggle switch to run the plow lights. Crewn knows the wiring better that I do, you can go into the fisher site and get the wiring diagrams, and go from there.
 

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what I have told guys in the past running old stuff, trying to save a few bucks. Just run a toggle switch to run the plow lights. Crewn knows the wiring better that I do, you can go into the fisher site and get the wiring diagrams, and go from there.
disclaimer, the harnesses came off a 90 gmc w/t with single sealed beams, I have the poly capsules on mine. I modified the harness to save a few hundred bucks. I MAY have goofed up, BUT, I've made alit of harnesses and I'm pretty savvy with that stuff.!

Yeah, aint no way is cwren getting sucked down that rabbit hole
 

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In an effort to be mildly helpful, your issue is that you crossed the ground and hot wires somewhere in the harness you scabbed together. That is always what causes the high/low to come on together. Where you screwed it up, I have no idea. The easiest solution would be to what dieseldude said and eliminate the connections to the headlights entirely and just hardwire them to a switch.
 

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Discussion Starter #5
So today I did some more investigation. I have power only on the park lead and low beam leads at the module on low beam. I have power only at the park and hi beam leads on high beam. I verified my ground in the truck harness on the pass side, which is the problem side. I have power to hi and lo at the bulbs in appropriate positions. On high beam though, the low beam power wire seems to switch to a ground? So I think that's my issue........keep in mind I did testing with a test light so there's a good indicator of amps. I switched the ds and ps light harness at the module, problem persisted, but seemed to switch sides..........so am I accurate to say I believe it's the module?
 

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Discussion Starter #7
I found a schematic for a four port module with and without hb-3/hb-4 lights. The colors don't match up with except hb-3/hb-4 lights and my wiring orientation doesn't match up with the hb-/hb-4 lighting schematic so maybe I'll try to repin my connectors......I just don't understand why my driverside works the way it's supposed to and it's wired exactly the same as my passenger side🤔
 

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Discussion Starter #9
I assume you mean the orientation plug for common + vs common - ? Also it's worth adding, and I forgot to, that when switching ds and ps harnesses at the module, the problem remains the same but switches sides of the truck......so I think it's in the module......maybe.....
 

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So today I did some more investigation. I have power only on the park lead and low beam leads at the module on low beam. I have power only at the park and hi beam leads on high beam. I verified my ground in the truck harness on the pass side, which is the problem side. I have power to hi and lo at the bulbs in appropriate positions. On high beam though, the low beam power wire seems to switch to a ground? So I think that's my issue........keep in mind I did testing with a test light so there's a good indicator of amps. I switched the ds and ps light harness at the module, problem persisted, but seemed to switch sides..........so am I accurate to say I believe it's the module?
No. If you switch the
 

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Discussion Starter #12
Ok so somehow the wiring didn't match up with the info schematics I found but after an hour or two of back tracking, back probing and tracing, I found the issue. I had to switch the yellow and dark blue with each other and orange and lt blue with each other at the module. Hooked up the orientation plug accordingly and presto! Fixed. Thanks for all the help guys!!!!
 
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