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#1 |
Registered User
Join Date: Apr 2002
Location: Manitoba, Canada
Posts: 663
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LMC Heavy Duty Headlight Wiring Harness
Just installed LMC’s Heavy Duty Headlight Wiring Harness. The install went well except for one of the ground wires was too short - easy fix. When I turned on the headlights I found that the high beams worked fine, but I have no low beams. Anyone familiar with this setup? Advice to solve the problem?
__________________
Present: 2015 Tacoma. Yeah, not a GM, but I love it. 1969 GMC 32,000 - fix, drive, relax, fix... 2019 BMW R1250 GSA - Yahoooooooo 1979 Honda GL 1000 - retro touring at its best. Past: '05 Sierra 4x4 - Had 270,000 KM and running well when it was written-off by a stop sign runner. '94 F-150 from the "F word" company. I'll admit it...good truck. Sold what was left of it for $800 to a guy who came to pick it up at 11:00 PM with cash in hand. Hmm. '79 Sierra Grande (Black) organ donor - perfect rebuildable 4-bolt 350 and a good TH350. '76 Sierra Grande (Orange) - hate isn't too strong a word. Kid who bought it turned it into a hot rod. '68 C-10 R.I.P. - Dad's old truck...too far gone to resurrect. '59 C-50 - with hoist. Truck is gone, wife isn't. Nuff said. |
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#2 |
Registered User
Join Date: Jun 2015
Location: @
Posts: 890
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Re: LMC Heavy Duty Headlight Wiring Harness
try switching the relays to see if you got lows and no high if so its a bad relay if not going to have to check wire harness
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#3 |
Registered User
Join Date: Feb 2018
Location: Doland SD
Posts: 836
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Re: LMC Heavy Duty Headlight Wiring Harness
I bought on on ebay for $20 for my gmc had no problems.
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![]() 94 chevy k1500 350 tbi 373 rear gears 4l60e one wheel peel. Gutless 07 gmc sierra classic rcsb 4.3 lt 5 speed w/t 04 chevy Silverado 1500 ext cab 5.3 4l60e. 81 chevy Scottsdale k10 muncie sm465 Np208 10 bolt 8.2 ( Old Green) |
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#4 |
Registered User
![]() Join Date: Mar 2017
Location: yucca valley
Posts: 239
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Re: LMC Heavy Duty Headlight Wiring Harness
Make sure the relays are not swapped one should be a 4 prong other should be 5 prong relay. I had the same problem .
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#5 |
Registered User
Join Date: Jan 2003
Location: Safford,AZ
Posts: 3,612
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Re: LMC Heavy Duty Headlight Wiring Harness
And don't forget a fuse for them, if you haven't put one in already.
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#6 |
Registered User
Join Date: Apr 2002
Location: Manitoba, Canada
Posts: 663
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Re: LMC Heavy Duty Headlight Wiring Harness
Thanks for the advice. I hadn’t thought of the relays.
__________________
Present: 2015 Tacoma. Yeah, not a GM, but I love it. 1969 GMC 32,000 - fix, drive, relax, fix... 2019 BMW R1250 GSA - Yahoooooooo 1979 Honda GL 1000 - retro touring at its best. Past: '05 Sierra 4x4 - Had 270,000 KM and running well when it was written-off by a stop sign runner. '94 F-150 from the "F word" company. I'll admit it...good truck. Sold what was left of it for $800 to a guy who came to pick it up at 11:00 PM with cash in hand. Hmm. '79 Sierra Grande (Black) organ donor - perfect rebuildable 4-bolt 350 and a good TH350. '76 Sierra Grande (Orange) - hate isn't too strong a word. Kid who bought it turned it into a hot rod. '68 C-10 R.I.P. - Dad's old truck...too far gone to resurrect. '59 C-50 - with hoist. Truck is gone, wife isn't. Nuff said. |
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#7 |
Registered User
Join Date: Apr 2002
Location: Manitoba, Canada
Posts: 663
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Re: LMC Heavy Duty Headlight Wiring Harness
The relays are identical. Both of the plugs that go into the relays have 4 plugs.
__________________
Present: 2015 Tacoma. Yeah, not a GM, but I love it. 1969 GMC 32,000 - fix, drive, relax, fix... 2019 BMW R1250 GSA - Yahoooooooo 1979 Honda GL 1000 - retro touring at its best. Past: '05 Sierra 4x4 - Had 270,000 KM and running well when it was written-off by a stop sign runner. '94 F-150 from the "F word" company. I'll admit it...good truck. Sold what was left of it for $800 to a guy who came to pick it up at 11:00 PM with cash in hand. Hmm. '79 Sierra Grande (Black) organ donor - perfect rebuildable 4-bolt 350 and a good TH350. '76 Sierra Grande (Orange) - hate isn't too strong a word. Kid who bought it turned it into a hot rod. '68 C-10 R.I.P. - Dad's old truck...too far gone to resurrect. '59 C-50 - with hoist. Truck is gone, wife isn't. Nuff said. |
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#8 |
Registered User
Join Date: Jun 2015
Location: @
Posts: 890
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Re: LMC Heavy Duty Headlight Wiring Harness
mine is from lmc also it has only 4 on both . the extra pin is for a normally closed circuit . you shouldn't need the extra pin because you have a dimmer switch that feeds power to one relay or the other . if it is wired correctly it wouldn't matter if you used a 4 pin or 5 pin relay the connector wouldn't have a wire for the pin so either would work as long as it was rated for the same amperage
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#9 |
Who Changed This?
![]() Join Date: Jan 2013
Location: Simi Valley, CA
Posts: 10,388
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Re: LMC Heavy Duty Headlight Wiring Harness
I installed this kit recently. I went and looked, and discovered it does not have fuses. I'll be adding fuses into the circuits. Good info!
__________________
~Steven '70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper Simi Valley, CA |
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#10 | |
Registered User
Join Date: Aug 2018
Location: Columbus, Ohio
Posts: 69
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Re: LMC Heavy Duty Headlight Wiring Harness
Quote:
where in the circuit I should install the fuses and what rating fuses would be appropriate. Thanks! ![]() |
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#11 |
Registered User
Join Date: Feb 2011
Location: Parkville, MD
Posts: 1,024
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Re: LMC Heavy Duty Headlight Wiring Harness
Wrote out a long post that didn't post. shorter version...
Test the power coming out of the head light switch. Test each of the inputs to the relays. Swap relays to see if the problem follows the relay. If you remove and reinstall the relays while the headlights are on, you should hear the relay click as power is applied. Fuses, I like to install as close to the battery or junction as possible. Headlights should draw around 10A. 15-20A should be good.
__________________
1970 C20 Custom Camper - 350, TH350 1997 GMC Suburban 1994 Acura Integra GSR 1987 Dodge Daytona Shelby Z |
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#12 |
Registered User
Join Date: Aug 2018
Location: Columbus, Ohio
Posts: 69
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Re: LMC Heavy Duty Headlight Wiring Harness
Thank you rpmerf! That is what I was thinking, but it never hurts to get an expert opinion.
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#13 |
Who Changed This?
![]() Join Date: Jan 2013
Location: Simi Valley, CA
Posts: 10,388
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Re: LMC Heavy Duty Headlight Wiring Harness
Just got back to this thread. I haven't put any fuses in yet, since I have been doing other things. Thanks rpmerf for the information!
__________________
~Steven '70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper Simi Valley, CA |
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headlight, lmc, wiring |
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