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

ShortyStep71 · 09-01-2007, 03:16 PM

has anybody bought the heavy duty headlight harness in LMC truck magazine? and how well does it work. and how easy is the installation?

basketcase · 09-01-2007, 04:46 PM

It's on my list for my truck. On a normal harness the full power to your lamps has to pass through your light switch to get to the headlights. This causes heat in the switch and voltage drop by the time it gets to the lights. This is easy to see on that low voltage yard lighting you see so much of these days. The further from the power source on 12v DC circuits the dimmer the light will be. Every plug or switch DC current passes through reduces the voltage as well as there is also a certain drop per foot of wire.

The LMC harness uses a relay to supply power to the lights. Your dash mounted light switch then uses lower apmerage to close the relay when you turn the lights on. Look at the relay as a wall switch. Your dash mounted switch now just takes the place of your finger turning on the lights. Current now goes from the battery to the relay to the lights. End result is the switch runs cooler and the power to the lights has a shorter and more direct path to the lights resulting in a brighter light. This is a big plus if you are running high power lights.

I ran landing lights in my '67 Corvette high beams and the load caused the circuit breaker to cut out after about 10 minutes. The relay system would have cured this.

I understand it is a plug in installation. I was thinking that I was going to have to make up my own harness for a relay to run my Hella headlights but LMC has done it for me.

Tom

Musclerodz · 09-01-2007, 05:01 PM

They work, but it is Chinese crap and the instructions are hard to read and misspelled. We offer one from AAW, it is twice the price but Aerican Made!

Mike

airdale94 · 09-01-2007, 05:12 PM

Quote:

Originally Posted by Musclerodz

They work, but it is Chinese crap and the instructions are hard to read and misspelled. We offer one from AAW, it is twice the price but Aerican Made!

Mike

Is that the "Universal Relay Kit" PN:500142 ?

Are the directions speciffic for headlight?

ShortyStep71 · 09-01-2007, 05:37 PM

yeah i know, i bought the one in LMC and it looks good but the instructions for installation are junk.

Musclerodz · 09-01-2007, 05:56 PM

Quote:

Originally Posted by airdale94

Is that the "Universal Relay Kit" PN:500142 ?

Are the directions speciffic for headlight?

No, it is 500403 and it is a specific headlight relay kit

basketcase · 09-01-2007, 06:40 PM

Thanks for the info. I'd much rather buy American when I can.

ShortyStep71 · 09-01-2007, 07:35 PM

ok i installed the harness and turned my light on and everything worked great and the low and high beams worked now i turned them off but they are still on. anyone know what the problem might be?

basketcase · 09-01-2007, 08:20 PM

The relay is still on. First I'd unplug the harness to the dash switch. That would isolate the relay and tell you if the relay is stuck on or if the problem is in the dash switch circuit. Check your wiring to be sure it's right.

Tom

airdale94 · 09-02-2007, 02:15 AM

Quote:

Originally Posted by Musclerodz

No, it is 500403 and it is a specific headlight relay kit

Sorry, I'm not finding it.

KFreddy · 09-02-2007, 03:03 AM

Quote:

Originally Posted by airdale94

Sorry, I'm not finding it.

Like wise, "No, it is 500403 and it is a specific headlight relay kit," is not on the site...

basketcase · 09-02-2007, 06:27 PM

I couldn't find it either.

xshadow · 09-02-2007, 07:27 PM

is it 36-3580 $29.99

xshadow · 09-02-2007, 07:28 PM

Let us know how it works out for you. I'm thinking about buying one or two harnesses.

PanelDeland · 09-02-2007, 07:50 PM

In the FAQ's section on the board there is a write up on this mod using common auto staore parts.It seems like it was inexpensive and had relays etc. you could replace easily if you ever needed to.

airdale94 · 09-02-2007, 10:37 PM

Quote:

Originally Posted by PanelDeland

In the FAQ's section on the board there is a write up on this mod using common auto staore parts.It seems like it was inexpensive and had relays etc. you could replace easily if you ever needed to.

I remember seeing that. Good writeup. Just thought if if I could get a a kit with instructions.

Musclerodz · 09-04-2007, 01:15 PM

http://0193647.netsolstores.com/inde...D&ProdID=27807

Mike

70 net440 · 09-04-2007, 08:53 PM

I followed the write up in the FAQ with Bosch relays I got at the local parts store. Installed on my kid's '67 and it worked great.

JWPOORE · 09-04-2007, 11:01 PM

What kit would be recommended as the best/easiest option? Here is another kit that was posted on another thread about this subject: http://www.madelectrical.com/catalog/rly-1.shtml I am assuming you would need to order two of these for it to work. I am just looking for the most straight forward and best quality option there is out there without having to run around looking for pieces to make a kit, plus I am pretty clueless on doing this so the easier the better.

JWPOORE · 09-05-2007, 07:45 PM

Thanks for any opinions/suggestions on the best kit to go with.

airdale94 · 09-09-2007, 11:39 PM

I think I'm going to go with "matt67350" 's writeup in the FAQ. Then follow "TxFirefighter" 's advice and make a trip to the junkyard. At $65 and $10 S&H, I'm going to try and save a little money. Mine's just a driver work truck though.

Thank's "Musclerodz" though for the link and info. Going to be looking into one of your wiring harnesses though.

09-01-2007, 03:16 PM	#1
ShortyStep71 Registered User Join Date: Aug 2007 Location: Clovis, New Mexico Posts: 18	Heavy Duty Headlight Harness? has anybody bought the heavy duty headlight harness in LMC truck magazine? and how well does it work. and how easy is the installation? Last edited by ShortyStep71; 09-01-2007 at 03:54 PM.

09-01-2007, 04:46 PM	#2
basketcase Registered User Join Date: Oct 2001 Location: Edgerton OH USA Posts: 627	Re: Heavy Duty Headlight Harness? It's on my list for my truck. On a normal harness the full power to your lamps has to pass through your light switch to get to the headlights. This causes heat in the switch and voltage drop by the time it gets to the lights. This is easy to see on that low voltage yard lighting you see so much of these days. The further from the power source on 12v DC circuits the dimmer the light will be. Every plug or switch DC current passes through reduces the voltage as well as there is also a certain drop per foot of wire. The LMC harness uses a relay to supply power to the lights. Your dash mounted light switch then uses lower apmerage to close the relay when you turn the lights on. Look at the relay as a wall switch. Your dash mounted switch now just takes the place of your finger turning on the lights. Current now goes from the battery to the relay to the lights. End result is the switch runs cooler and the power to the lights has a shorter and more direct path to the lights resulting in a brighter light. This is a big plus if you are running high power lights. I ran landing lights in my '67 Corvette high beams and the load caused the circuit breaker to cut out after about 10 minutes. The relay system would have cured this. I understand it is a plug in installation. I was thinking that I was going to have to make up my own harness for a relay to run my Hella headlights but LMC has done it for me. Tom __________________ '69 swb stepside in progress. '59 Corvette lifetime project Last edited by basketcase; 09-01-2007 at 04:47 PM.

09-01-2007, 05:01 PM	#3
Musclerodz Senior Member Join Date: Aug 2005 Location: OKC, OK Posts: 2,365	Re: Heavy Duty Headlight Harness? They work, but it is Chinese crap and the instructions are hard to read and misspelled. We offer one from AAW, it is twice the price but Aerican Made! Mike __________________ Mike Redpath Last edited by Musclerodz; 09-01-2007 at 05:02 PM.

09-01-2007, 05:37 PM	#5
ShortyStep71 Registered User Join Date: Aug 2007 Location: Clovis, New Mexico Posts: 18	Re: Heavy Duty Headlight Harness? yeah i know, i bought the one in LMC and it looks good but the instructions for installation are junk.

09-01-2007, 06:40 PM	#7
basketcase Registered User Join Date: Oct 2001 Location: Edgerton OH USA Posts: 627	Re: Heavy Duty Headlight Harness? Thanks for the info. I'd much rather buy American when I can.

09-01-2007, 07:35 PM	#8
ShortyStep71 Registered User Join Date: Aug 2007 Location: Clovis, New Mexico Posts: 18	Re: Heavy Duty Headlight Harness? ok i installed the harness and turned my light on and everything worked great and the low and high beams worked now i turned them off but they are still on. anyone know what the problem might be? Last edited by ShortyStep71; 09-01-2007 at 08:13 PM.

09-01-2007, 08:20 PM	#9
basketcase Registered User Join Date: Oct 2001 Location: Edgerton OH USA Posts: 627	Re: Heavy Duty Headlight Harness? The relay is still on. First I'd unplug the harness to the dash switch. That would isolate the relay and tell you if the relay is stuck on or if the problem is in the dash switch circuit. Check your wiring to be sure it's right. Tom

09-02-2007, 06:27 PM	#12
basketcase Registered User Join Date: Oct 2001 Location: Edgerton OH USA Posts: 627	Re: Heavy Duty Headlight Harness? I couldn't find it either.

09-02-2007, 07:27 PM	#13
xshadow Registered User Join Date: Apr 2006 Location: va Posts: 553	Re: Heavy Duty Headlight Harness? is it 36-3580 $29.99 Last edited by xshadow; 09-02-2007 at 07:27 PM.

09-02-2007, 07:28 PM	#14
xshadow Registered User Join Date: Apr 2006 Location: va Posts: 553	Re: Heavy Duty Headlight Harness? Let us know how it works out for you. I'm thinking about buying one or two harnesses.

09-02-2007, 07:50 PM	#15
PanelDeland I am a Referee of life. Join Date: Jun 2000 Location: Greensboro N.C. Posts: 13,993	Re: Heavy Duty Headlight Harness? In the FAQ's section on the board there is a write up on this mod using common auto staore parts.It seems like it was inexpensive and had relays etc. you could replace easily if you ever needed to. __________________ The 47-present Chevrolet and GMC Truck Message Board Network,it's owners,moderators,members,and associates of any type should not be held responsible for my opinion. You can't fix stupid,not even with duct tape. "My appearance is due to the fact that "GOD" does punish you for having too much fun!" Barrett-Jackson has perfected alchemy,they make rust into gold! "You can lead a horse to water but you can't saddle a duck" "Cleverly disguised as a 'Responsible Adult' "Sometimes your Knight in shining armor is just a retard in tinfoil"

09-04-2007, 01:15 PM	#17
Musclerodz Senior Member Join Date: Aug 2005 Location: OKC, OK Posts: 2,365	Re: Heavy Duty Headlight Harness? http://0193647.netsolstores.com/inde...D&ProdID=27807 Mike __________________ Mike Redpath

09-04-2007, 08:53 PM	#18
70 net440 Junior Member Join Date: Sep 2003 Location: yreka, ca Posts: 270	Re: Heavy Duty Headlight Harness? I followed the write up in the FAQ with Bosch relays I got at the local parts store. Installed on my kid's '67 and it worked great. __________________ 63 C10 70 Coronet R/T 67 C10 70 Dart Swinger 71 K10

09-04-2007, 11:01 PM	#19
JWPOORE Registered User Join Date: Nov 2006 Location: Central Valley, CA Posts: 198	Re: Heavy Duty Headlight Harness? What kit would be recommended as the best/easiest option? Here is another kit that was posted on another thread about this subject: http://www.madelectrical.com/catalog/rly-1.shtml I am assuming you would need to order two of these for it to work. I am just looking for the most straight forward and best quality option there is out there without having to run around looking for pieces to make a kit, plus I am pretty clueless on doing this so the easier the better.

09-05-2007, 07:45 PM	#20
JWPOORE Registered User Join Date: Nov 2006 Location: Central Valley, CA Posts: 198	Re: Heavy Duty Headlight Harness? Thanks for any opinions/suggestions on the best kit to go with.



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09-09-2007, 11:39 PM	#21
airdale94 Registered User Join Date: Jan 2007 Location: Topeka,KS Posts: 778	Re: Heavy Duty Headlight Harness? I think I'm going to go with "matt67350" 's writeup in the FAQ. Then follow "TxFirefighter" 's advice and make a trip to the junkyard. At $65 and $10 S&H, I'm going to try and save a little money. Mine's just a driver work truck though. Thank's "Musclerodz" though for the link and info. Going to be looking into one of your wiring harnesses though. Last edited by airdale94; 09-09-2007 at 11:41 PM. Reason: add

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