Major headlight upgrade for GMC trucks

[snowblind]

Hi everybody.

I thought I would toss this out there for anyone who is interested in upgrading the headlights in their GMC.

I am having a custom wiring harness made that will allow me to run 4 x low/high beam headlights instead of the stock 2 x low/highs and 2 x high only. Installation involves NO CUTTING of the stock wiring. The new harness is custom made to accept the old headlight connectors as the turn on signal for the new relays. Headlight power will now go directly from the alt/battery with minimal current going through the stock headlight switch.

My harness is being made by Susquehanna Motorsports http://www.rallylights.com/ They specialize in rally and race car lighting and use only Hella relays and connectors. I was quoted $130 for one harness. Obviously the price will go down the more harnesses I order.

It would definitely be less expensive to buy the relays separately and wire it all yourself but this will be a slick harness and leave the stock wiring untouched.

Shoot me a PM if anyone is interested in ordering with me.


Matt

[cdowns]

you may run into police problems on the road

[snowblind]

Originally Posted by cdowns

you may run into police problems on the road

****Off-hwy use only of course****

To avoid bothering other off-hwy drivers I plan to aim one set as low as possible and the other set just a teeny bit higher. I'm not looking to blind anyone I just need more low beam light. I rarely use high-beams.

Is there a DOT law specifically against 4 low beam headlights? I feel like I see people running like that all the time...

[69GMCLonghorn]

Originally Posted by cdowns

you may run into police problems on the road

From what I understand, you can have 4 headlights on as long as they are not on high beam. I did a similar conversion on my '95 Chevy truck, but kind of backwards... When you hit the high beams, the low beams turned off. The relay setup that I bought for that, allowed all 4 lights to stay on when the high beams came on, but didn't allow for 4 lights on low beam due to the high beam lights not being 2 stage...

[snowblind]

Originally Posted by 69GMCLonghorn

From what I understand, you can have 4 headlights on as long as they are not on high beam.

Isn't the stock set up 4 x high beam and then 2 x on low beam? That's how my Jimmy is and the wiring looks unmolested?

[mr48chev]

Originally Posted by snowblind

Isn't the stock set up 4 x high beam and then 2 x on low beam? That's how my Jimmy is and the wiring looks unmolested?

Yep but it could easily be wired for two low. four high or four low/four high.

All it would take is Two three prong sockets, two extra high beams, a relay to run the inside low beams when you wanted them on and a switch to activate the relay. The power side of the relay would be wired into the low beam circuit. I'd suggest high and low beam relays though to make sure that the extra amps. Plus any lights that throw out extra light would draw more amps.

The lights in my 71 run H-4 bulbs and throw good light but tend to eat dimmer switches.

[Longhorn Man]

4 high and 2 low.
I'd bet a kick in the pills that 4 low would not be legal... almost positive.
Just adjusting them alone will do wonders, and then relays and normal haligon sealed beams (I recomend sylvania's silver star) and you will be seeing everything.

[byrd]

Originally Posted by snowblind

Hi everybody.

I thought I would toss this out there for anyone who is interested in upgrading the headlights in their GMC.

I am having a custom wiring harness made that will allow me to run 4 x low/high beam headlights instead of the stock 2 x low/highs and 2 x high only. Installation involves NO CUTTING of the stock wiring. The new harness is custom made to accept the old headlight connectors as the turn on signal for the new relays. Headlight power will now go directly from the alt/battery with minimal current going through the stock headlight switch.

My harness is being made by Susquehanna Motorsports http://www.rallylights.com/ They specialize in rally and race car lighting and use only Hella relays and connectors. I was quoted $130 for one harness. Obviously the price will go down the more harnesses I order.

It would definitely be less expensive to buy the relays separately and wire it all yourself but this will be a slick harness and leave the stock wiring untouched.

Shoot me a PM if anyone is interested in ordering with me.


Matt

Using standard 12 volt auotmotive relays(they sell for around $5-6 bucks/each at Radioshack), and an intenally regulated alt will make a HUGE difference. I will venture to say the candle power was 3-4 times as what it was with the stock set up. There is no need for 4 low beams and I, like longhornman suspect you will have problems with po-po.

BTW LMC sells(others do too just was easier to link to) the premade harness with no splicing for the GMC truck and it is only $30. Get you a internally reg alt conversion and a new alt and you are still out less than the $130 you were quoted and will be legal, and just as bright.

http://www.lmctruck.com/icatalog/cb/full.aspx?Page=74

I have used the harness(took it out as I didn't need it) and found that if you would spend some time making sure all your grounds are excellent and you swap to an internal reg alt, that you really do not need the harness...... jmho...Randy

[mrein3]

Originally Posted by byrd

Using standard 12 volt auotmotive relays(they sell for around $5-6 buack/each at Radioshack), and an intenally regulated alt will make a HUGE difference. I will venture to say the candle power was 3-4 times as what it was with the stock set up. There is no need for 4 low beams and I, like longhornman suspect you will have problems with po-po.

BTW LMC sells(others do too just was easier to link to) the premade harness with no splicing for the GMC truck and it is only $30. Get you a internally reg alt conversion and a new alt and you are still out less than the $130 you were quoted and will be legal, and just as bright.

http://www.lmctruck.com/icatalog/cb/full.aspx?Page=74

I have used the harness(took it out as I didn't need it) and found that if you would spend some time making sure all your grounds are excellent and you swap to an internal reg alt, that you really do not need the harness...... jmho...Randy

I will disagree with one thing above. You do need to do the relay harness. Without it the factory wiring runs too much current through too small a wire when you turn on your headlights - high beam or low beam. By putting the relays in you are no longer pulling current through over 20 feet of 16 gauge wire to run your headlights. I'm not sure about the linked harness but a decent one will run a 12 or 10 gauge wire from the battery to each relay, then from the hot when energized leg of the relay right to the headlight.

In stock form on my truck I measured 10.5 volts at the headlight. Through relays you're at full battery voltage which is 12 to 14.5 volts (or more if your stock voltage regulator is out of whack. )

All that current drop in the stock wiring produces heat. Heat kills the contacts in your headlight switch.

I wish that pre-made LMC harness was available when I rolled my own harness. I don't have $30 into my setup but time is money. That $30 LMC kit appears to have both relays included which like byrd points out are about $5 each. So you're really only paying $20 for the harness.

As others have pointed out:
1. Do the relay upgrade. (No more burning out your headlight switch)
2. Install halogen sealed beams. (50 state street legal)
3. Adjust your headlights.

Disclaimer: I don't work for or have any financial interest in LMC.

[snowblind]

Thanks for all the great input guys. I have a 100 amp 1 wire alternator and I will be running Hella "E-code" headlamps with replaceable 55w/65w bulbs.

The reason I want the four lows is because I regularly drive a dark and windy mountain road that is strewn with rocks and boulders. It's usually snowing and the road has regular traffic coming the other way so high beams really aren't an option. In my previous vehicle I ran a pair of the Hella Euro H4 headlights and a set of Micro DE fog lights. The combo was bright and I really liked the sharp cut-off but I still felt the need for more total light.

I don't really want to mount axillary lights on the grill of the Jimmy so I saw this as a decent alternative. Since this harness would be custom I'm thinking I may go one step further and wire the second set of lows on a separate relay. Then I could use a toggle switch to independently turn on the second set of lows.

Thanks for the heads up on the LMC harness. Looking at that link the GMC headlights they sell actually all ship with low/high bulbs but have a wiring adapter that leaves the lows off in the second set!!! If I wasn't going for 4 lows I would probably use that harness and save some money but for me it's really a choice between 4 upgraded lows or 2 upgraded lows PLUS a set of auxiliary lights.

[JJanzen]

Byrd,
On the LMC harness upgrade, does that run from the external regulator or does it originate from somewhere else. I am just getting to that point on my build and don't yet fully understand the headlight/engine compartment harness/setup. Thanks for the help.
Joel

[byrd]

Originally Posted by JJanzen

Byrd,
On the LMC harness upgrade, does that run from the external regulator or does it originate from somewhere else. I am just getting to that point on my build and don't yet fully understand the headlight/engine compartment harness/setup. Thanks for the help.
Joel

The harness directly connects to your battery and plugs into your existing headlight connector and it all works by plug and play. The only part you have to physically connect is to the battery.
You might want to pull the battery out to install the realys behind it on the core support to conceal them, other than that is should take about 15-30 minutes to install the whole set up depending on how much time you spend trying to hide the harness.

[snowblind]

Hey Everybody.

I wanted to share these photos from yesterday. I discovered another drawback of the stock low beam set up. Snow and ice build up on the high beam when not in use making it pretty much useless when you do need it.

[Stocker]

Hey.... is that hood cracked open??

[mrein3]

Originally Posted by snowblind

Hey Everybody.

I wanted to share these photos from yesterday. I discovered another drawback of the stock low beam set up. Snow and ice build up on the high beam when not in use making it pretty much useless when you do need it.

pictures snipped

Proving once again that two headlights are better than 4.
JK.

The global warmers out there are right now discovering that all those LED stoplights they installed to save our mother the earth don't melt snow either and now folks are crashing into each other at intersections
http://wcco.com/wireapnewswi/High.ef...2.1363896.html

You can't make this stuff up fast enough.

[Longhorn Man]

Randy, you pointed out something I usually mention, but failed to this time.
Clean the grounds on the core support.

[Longhorn Man]

you can aim them higher if you want, any direction you feel the need to aim them.