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Discussion Starter · #1 ·
Hi - and I sure hope someone can point me in the right direction. Last year, just before the snow finally left, my passenger side (Rt.) plow headlight quit. New bulb did not help. A couple mechanic friends of mine suspected either the 11 pin harness or the module might be bad or even both of them. I just replaced both items today. At some point one of them evidenlty plugged the A-B-C harness wires into the module wrong. Once I plugged them in the right ports, I finally had power back to the fishstick and I could operate the plow. But now I have this lighting problem.
Now when I hook the plow up, the passenger side plow headlight comes one and the truck's passenger side headlight goes out. However, the driver side truck headlight stays on and the drivers side plow light does not. Switching between hi and lo beam makes no difference at all. Sadly, I just had back surgery a week ago and can't crawl around in or on a truck for 6-8 weeks and I'm pretty sure up in northern NY state, we're gonna have snow by then.
The truck is a 2011 GMC Sierra 1500 regular cab, 8ft box and included the plow package when I bought it new in 2011. It's worked flawlessly since it was new, until this issue came in to play. So, to sum up - the passenger side is now doing what it's suppose to and shutting off the truck's headlight and turning on the plow's headlight, but on the driver's side, the truck headlight stays on and the plow light does not come on. Remember, brand new harness from a Fisher dealer and brand new 3 port module.
One more oddity. When I pulled the truck into my shop so y wife could swap out the module, she noticed the A, B, and C harness sets were NOT plugged into the properly marked ports. I think the last mechanic who worked on it may have tried this to see if it made a difference and then forgot to switch it back because I went and picked up the truck. Anyway, we plugged the harnesses into the proper ports and I finally had lights, but the problem above was happening now.
I hope to God someone can point me in the right direction. I have to have my talented wife do the work because of the surgery so it's exasperating that I can't do it myself. I'm appealing to all on the forum. You'd think at 70 years old, I know all this stuff by now. LOL!! I'm always up to learn new stuff though. Please, if you can, help me out??
 

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Discussion Starter · #2 ·
Sorry...one more thing . . . it's a Fisher HT model plow and the truck is a 2011 GMC Sierra 1/2 ton truck with plow package from factory installed and always worked perfectly. Thanks again! Hope you can help me out here. Doug
 

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Check the connectors at the factory truck headlight - I'll wager even money that someone disconnected the plow harness while f'ing around with it to diagnose it and never plugged the truck harness back into the plow harness on that side.

edit: especially if someone was stupid enough to swap the connectors at the module blindly and not putting them back before they were finished. Kudos to your wife for being more observant than they were.
 

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Discussion Starter · #4 ·
Check the connectors at the factory truck headlight - I'll wager even money that someone disconnected the plow harness while f'ing around with it to diagnose it and never plugged the truck harness back into the plow harness on that side. edit: especially if someone was stupid enough to swap the connectors at the module blindly and not putting them back before they were finished. Kudos to your wife for being more observant than they were.
Thanks! This sounds about right. I had it out at a garage last spring because I couldn't do it due to a back injury. I just had surgery FINALLY to get it fixed and can't do too much yet. Drives me nuts that I can't squeeze in and around anything to check it out - especially since I've always done my own work since forever. I think you're on to something here and will check it out ASAP in my shop right away. If I find anything, I'll let you know back. And yeah, I thought it was odd that the harnesses weren't properly connected. I had taken it off, not thinking he'd need it on to test things, and never gave it a thought. I bet you're right and once I get into it again, I'll post it on here.
 
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