Heavy Duty Headlight Harness. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

ryhan87 · 11-30-2010, 11:41 PM

I was looking in the LMC catalog and noticed there heavy duty headlight harness. I was thinking about doing this myself. I can get all the wire and relays i need to do it through work for free. I was just wondering if anyone has done this and did you notice quite a difference in your light output?

Valhalla · 11-30-2010, 11:42 PM

If you use the search there are several threads on it.

**LockDoc** · 11-30-2010, 11:48 PM

-
I just upgraded the Green '67 with parts I got over at the salvage yard. I think it was a good improvement...

LockDoc

**Clyde65** · 12-01-2010, 11:52 AM

I have also been looking into this since I upgraded my headlights to the H4 bulbs from sealed beam. I am also looking at this harness, looks almost identical...

http://www.eautoworks.com/product-eA...com-189849.htm

**Already Gone** · 12-01-2010, 02:05 PM

I'm no mecahnic/technician and I did mine a few years ago with relays from a wrecked Dodge Caravan, some wiring, following directions I got from this site and an afternoons work and wow it does make big difference in the brightnes of your headlights.

mrein3 · 12-01-2010, 02:10 PM

Quote:

Originally Posted by ryhan87

I was looking in the LMC catalog and noticed there heavy duty headlight harness. I was thinking about doing this myself. I can get all the wire and relays i need to do it through work for free. I was just wondering if anyone has done this and did you notice quite a difference in your light output?

I got about $15 into my "heavy duty headlight harness". You WILL notice quite a difference in the light output.

Before you start, measure the voltage at one or both headlights with the factory wiring. After you're done measure it again. It has been a while but I believe my numbers were on the order of 10.8 or so volts factory, 13.4 with current coming off the battery through 10 gauge wire and a relay.

Forget the overpriced H4s and all those other lights. Get an $8 halogen at Wal*Mart. They will be considerably brighter than stock (stock wiring and headlights) and a heck of a lot cheaper. PLUS if/when one burns out you can get a replacement at ANY place that sells auto parts.

Another trick for this 'upgrade' is to go to NAPA and purchase a handful of part number 725147. This part number is for the little brass colored inserts that are in factory GM connectors from this vintage of GM. You can pop out the existing wire from the factory plug and replace it with your heavier wire from the relay.

Andy4639 · 12-01-2010, 11:00 PM

I did all of this myself. Bought the relays and wire and went for it. I even tied my driving lights into the relays. Run one heavy gauge wire to the drivers side and run both relays off of it. Tie into the drivers side light wires and it's done.

Jacfourteen · 12-02-2010, 02:19 AM

I say go for it, it will help out. Also it will prolong the life of your headlight switch because now it's only controlling the load of the coils in the relay, not the lights.

mrein3 · 12-02-2010, 08:24 AM

Quote:

Originally Posted by Jacfourteen

I say go for it, it will help out. Also it will prolong the life of your headlight switch because now it's only controlling the load of the coils in the relay, not the lights.

Correct. If your headlight switch is good now, you'll never have to replace it. If you stick with the stock wiring all that voltage drop is lost to heat. Wiring in relays to control the lights takes all this load out of your switch.

Sinister · 12-02-2010, 08:49 AM

I actually sprung for the LMC relays because I didn't want to cut up my stock harness. Plug and play, works good.

Lemield · 12-02-2010, 09:54 AM

I have the LMC harness in both my trucks. Big difference! The only complaint I have is that the LMC harness is an ugly yellow color....Easily solved with a utility knife and some black loom cover.

piecesparts · 12-02-2010, 12:12 PM

The heavy duty harness works to put 12 volts directly to the headlights. If the power goes through the headlight switch, then there is voltage drop, meaning that the headlights would not be as bright as they would be otherwise. The external wiring harness also means that you could use bulbs that draw more amperage, thus making a brighter driving experience.

mikemileski · 12-02-2010, 02:21 PM

I bought the LMC harness. For $29.95 it's plug-and-play and you don't have to hunt down the parts or do any cutting. I agree with the comment about it being bright yellow. I used the black split wire cover so it was less visible.

Mike Mileski
Tucson, AZ
'72 GMC SWB 4x4

71meangreenc10 · 12-02-2010, 03:06 PM

Using the LMC one, works good. Big Difference in Lights.

Smitty

mrein3 · 12-02-2010, 03:22 PM

Don't cut your harness. Just pick the side you want to mount the relays on. Slip low beam wire out of the headlight plug on that side. Slide that on as the control side of the low beam relay. Do the same for high. Then use the NAPA 725145 female connectors to make a 10 or 12 gauge wire plug into the headlight plug you took the control wires out of. I did this and left all my factory wiring uncut and in place.

mrein3 · 12-02-2010, 03:32 PM

I mean NAPA 725147. The 45 number is the male connector.

babylonflyer · 01-30-2011, 09:01 PM

did u ever use this harness????

Quote:

Originally Posted by Clyde65

I have also been looking into this since I upgraded my headlights to the H4 bulbs from sealed beam. I am also looking at this harness, looks almost identical...

http://www.eautoworks.com/product-eA...com-189849.htm

shiner2001 · 01-30-2011, 09:27 PM

I did this on my 73 Wagoneer a couple weeks ago and it made a huge difference. About to add relays to the truck, too. Instead of paying $6-7 per relay at O'Reilly or Advance (checked both of their prices last night), earlier today I ordered a lot of 10 relays off of Ebay for $10 shipped.

babylonflyer · 01-30-2011, 09:29 PM

links ??? info???

Quote:

Originally Posted by shiner2001

I did this on my 73 Wagoneer a couple weeks ago and it made a huge difference. About to add relays to the truck, too. Instead of paying $6-7 per relay at O'Reilly or Advance (checked both of their prices last night), earlier today I ordered a lot of 10 relays off of Ebay for $10 shipped.

Longhorn Man · 01-30-2011, 09:32 PM

The LMC harness has a couple drawbacks, the harness is a tick to short, and the relays are very cheap.
I made my own with GM relays out of a mid 90's P/30 in a junk yard... grabbed a couple extra relays for that just in case they blow, but that day has never come yet.
The difference is rather impressive. Your headlights will be white instead of orange. To one up it, grab a set of silver star headlamps, they are a bit expensive, but well worth it.

shiner2001 · 01-30-2011, 11:02 PM

Quote:

Originally Posted by babylonflyer

links ??? info???

Just search for "bosch relay" or "12v relay" or something similar, there are tons of auctions for relays by the lot.

This is the one I grabbed today.

11-30-2010, 11:41 PM	#1
ryhan87 Registered User Join Date: Sep 2009 Location: Lloydminster Alberta Posts: 32	Heavy Duty Headlight Harness. I was looking in the LMC catalog and noticed there heavy duty headlight harness. I was thinking about doing this myself. I can get all the wire and relays i need to do it through work for free. I was just wondering if anyone has done this and did you notice quite a difference in your light output?

11-30-2010, 11:42 PM	#2
Valhalla Registered User Join Date: Nov 2010 Location: Chandler, Arizona Posts: 295	Re: Heavy Duty Headlight Harness. If you use the search there are several threads on it. __________________ My build thread for Project TiC TaC/Jazzmin Oh Yeahhh Cheap work is never good and good work is never cheap. Lesson = learn to do it all the right way on your own. SqueegeeMan

11-30-2010, 11:48 PM	#3
LockDoc The Older Generation Join Date: Aug 2006 Location: Montezuma, Iowa Posts: 25,774	Re: Heavy Duty Headlight Harness. - I just upgraded the Green '67 with parts I got over at the salvage yard. I think it was a good improvement... LockDoc __________________ Leon Locksmith, Specializing In Antique Trucks, Automobiles, & Motorcycles (My Dually Pickup Project Thread) http://67-72chevytrucks.com/vboard/s...d.php?t=829820 - Last edited by LockDoc; 11-30-2010 at 11:49 PM.

12-01-2010, 11:52 AM	#4
Clyde65 1965 Chevy C10, 2005 4.8L/4l60 Join Date: Aug 2004 Location: DFW Texas Posts: 8,546	Re: Heavy Duty Headlight Harness. I have also been looking into this since I upgraded my headlights to the H4 bulbs from sealed beam. I am also looking at this harness, looks almost identical... http://www.eautoworks.com/product-eA...com-189849.htm __________________ Clyde65 Rebuild of Clyde http://67-72chevytrucks.com/vboard/s...84#post8338184 69 Aristocrat Lo Liner build http://67-72chevytrucks.com/vboard/s...84#post7561684 *support our troops!*

12-01-2010, 02:05 PM	#5
Already Gone 70+ ( Old Skool Club ) Join Date: Nov 2003 Location: Saskatoon, Saskatchewan ,Canada Posts: 9,143	Re: Heavy Duty Headlight Harness. I'm no mecahnic/technician and I did mine a few years ago with relays from a wrecked Dodge Caravan, some wiring, following directions I got from this site and an afternoons work and wow it does make big difference in the brightnes of your headlights. __________________ 1972 C10 Custom/Deluxe 613 Highlander 406/700R4 1999 White Tahoe LS 4x2 with Z56 Police Package 1992 K1500 GMC Suburban Members I have personally met: MusicMan70 - HeavyD - ChewyChevy67 - StingRay -71SWB4x4 - 67 Burb - DeadheadNM - too much stuff - bc65 - das601 " Circumsatances Do Not Change Responsibility " " The Sky is not the Limit, Your Mind is." Marilyn Monroe .. RIP Charlie Watts 1941 - 2021

12-01-2010, 11:00 PM	#7
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,945	Re: Heavy Duty Headlight Harness. I did all of this myself. Bought the relays and wire and went for it. I even tied my driving lights into the relays. Run one heavy gauge wire to the drivers side and run both relays off of it. Tie into the drivers side light wires and it's done. __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.

12-02-2010, 02:19 AM	#8
Jacfourteen Big Red - Now its a SWB! Join Date: Jun 2009 Location: Oroville, Ca Posts: 1,624	Re: Heavy Duty Headlight Harness. I say go for it, it will help out. Also it will prolong the life of your headlight switch because now it's only controlling the load of the coils in the relay, not the lights. __________________ 68 3/4 ton (Project)-350 Small Block, .030 over, 10:1 comp, 3998993 heads, C3BX edelbrock intake, comp cams XE268, Holley 670 SA, long tube headers, dual flow 40's, E-fan, Alum rad, currently under the knife getting shortened and bagged build thread 41 3/4 ton (wife's)-flatbed, fully restored to original 01 Tahoe LT 4WD (my daily driver)-Magnaflow Muffler, Rollin on 22's 02 Ford Mustang Convertable (Wife's Car)-Flowmaster 50, Clear corners, Intake, sittin on 18's

12-02-2010, 08:49 AM	#10
Sinister Between Trucks... Join Date: Mar 2002 Location: Los Angeles, CA. Posts: 3,830	Re: Heavy Duty Headlight Harness. I actually sprung for the LMC relays because I didn't want to cut up my stock harness. Plug and play, works good. __________________ Beat it to fit, Paint it to match...

12-02-2010, 09:54 AM	#11
Lemield Registered User Join Date: Dec 2004 Location: Arvada Colorado Posts: 1,321	Re: Heavy Duty Headlight Harness. I have the LMC harness in both my trucks. Big difference! The only complaint I have is that the LMC harness is an ugly yellow color....Easily solved with a utility knife and some black loom cover. __________________ Larry 1949 Willys CJ2A, Kubota Turbo Diesel engine, Warn Overdrive, 11 inch brakes, 12volt, Warn M8000 Winch "Little Green" 1970 Rustoleum Roller Red C20 Custom Camper 454 TH400 "Big Red" 1971 K20 6.2 Turbo Diesel 4x4 4spd Ranger Overdrive "Pumpkin Wagon" 2005 VW Beetle Diesel 44+ MPG "Silver Bullet"

12-02-2010, 12:12 PM	#12
piecesparts Parts and more parts Join Date: Nov 2003 Location: Lebo, Kansas (middle of nowhere Posts: 6,821	Re: Heavy Duty Headlight Harness. The heavy duty harness works to put 12 volts directly to the headlights. If the power goes through the headlight switch, then there is voltage drop, meaning that the headlights would not be as bright as they would be otherwise. The external wiring harness also means that you could use bulbs that draw more amperage, thus making a brighter driving experience. __________________ Frank

12-02-2010, 02:21 PM	#13
mikemileski Registered User Join Date: Jul 2009 Location: Tucson, AZ Posts: 66	Re: Heavy Duty Headlight Harness. I bought the LMC harness. For $29.95 it's plug-and-play and you don't have to hunt down the parts or do any cutting. I agree with the comment about it being bright yellow. I used the black split wire cover so it was less visible. Mike Mileski Tucson, AZ '72 GMC SWB 4x4

12-02-2010, 03:06 PM	#14
71meangreenc10 Its a Truck Thing...... Join Date: Dec 2004 Location: Sierra Vista, Arizona Posts: 3,179	Re: Heavy Duty Headlight Harness. Using the LMC one, works good. Big Difference in Lights. Smitty __________________ 71 C10 283/3SPD Full Resto 71 GMC 1500 Sierra Grande http://67-72chevytrucks.com/vboard/s...d.php?t=518599 70 C10 Suburban Former military GSA truck. 72 Chevy Blazer 4X4, Sloppy Jo, Mountain Climber. Wife says no more trucks. http://67-72chevytrucks.com/vboard/s...d.php?t=707378 72 GMC 1 Ton Motor Home, wife said no more trucks until she saw this one. Gen 3 6.0/4L80E 4.10 http://67-72chevytrucks.com/vboard/s...d.php?t=761110 68 GMC Suburban was 3/4 ton, now 1/2.Wife shook her head 71 C30 Wrecker 71 C20 Scott-Bilt As weird as it gets..BB Cheyenne AC Truck 68 GMC Long Stepside. They keep following me home 69 C30 Former Motor Home, Flat Bed time 70 G20 Red-E-Kamp Conversion "I'm your Boogy Van"

12-02-2010, 03:22 PM	#15
mrein3 Registered User Join Date: Feb 2000 Location: Center City, MN, USA Posts: 3,254	Re: Heavy Duty Headlight Harness. Don't cut your harness. Just pick the side you want to mount the relays on. Slip low beam wire out of the headlight plug on that side. Slide that on as the control side of the low beam relay. Do the same for high. Then use the NAPA 725145 female connectors to make a 10 or 12 gauge wire plug into the headlight plug you took the control wires out of. I did this and left all my factory wiring uncut and in place. __________________ '70 cab, '71 chassis, 383, TH350, NP205. '71 Malibu convertible '72 Malibu hard top Center City, MN

12-02-2010, 03:32 PM	#16
mrein3 Registered User Join Date: Feb 2000 Location: Center City, MN, USA Posts: 3,254	Re: Heavy Duty Headlight Harness. I mean NAPA 725147. The 45 number is the male connector. __________________ '70 cab, '71 chassis, 383, TH350, NP205. '71 Malibu convertible '72 Malibu hard top Center City, MN

01-30-2011, 09:27 PM	#18
shiner2001 Registered User Join Date: Sep 2010 Location: Fort Worth, TX Posts: 222	Re: Heavy Duty Headlight Harness. I did this on my 73 Wagoneer a couple weeks ago and it made a huge difference. About to add relays to the truck, too. Instead of paying $6-7 per relay at O'Reilly or Advance (checked both of their prices last night), earlier today I ordered a lot of 10 relays off of Ebay for $10 shipped. __________________ Derek 72 Chevy Cheyenne Super LWB 454 SS LS6 90 GMC Suburban V2500 350 ----------- 64 Chevy El Camino 357 73 Jeep Wagoneer 360 78 Jeep Cherokee 360 79 Scout II 345 88 Jeep Wrangler 4.2L 91 Jeep Wrangler 4.3L 98 Lincoln Mark VIII 4.6L 01 GMC Yukon 5.3L *"If it's not broken, fix it 'till it is!"*



Register or Log In To remove these advertisements.

01-30-2011, 09:32 PM	#20
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,690	Re: Heavy Duty Headlight Harness. The LMC harness has a couple drawbacks, the harness is a tick to short, and the relays are very cheap. I made my own with GM relays out of a mid 90's P/30 in a junk yard... grabbed a couple extra relays for that just in case they blow, but that day has never come yet. The difference is rather impressive. Your headlights will be white instead of orange. To one up it, grab a set of silver star headlamps, they are a bit expensive, but well worth it.

Register or Log In To remove these advertisements.