Headlight harness upgrade

[gogmorgo]

As Hornbrod said. You can cut and splice if you want, or you can just push male spade connectors into the socket. You keep it around because there's no reason not to. What you're doing is using the factory headlight wiring to trigger relays that switch on the headlights. It removes the load from the not-quite-up-to-task headlight wiring, while retaining all the factory switches, functions, etc. Whenever the headlights would have come on (i.e. power goes to the old headlight sockets), the relays are triggered so the headlights come on.

[cruiser54]

Let's make something real simple real complicated. 

[dustyinthedirt]

why excatly will the harness cause the switch to burn out? Improper gauge wire?

[cruiser54]

why excatly will the harness cause the switch to burn out? Improper gauge wire?

The stock one?

 

Because it is of small gauge wire and runs through the switch. Lots of resistance in the circuit and the switch has the breaker in it. 

[mikekaz1]

I like how you guys made it clear as to how to diy instructions, especially the drawn wiring diagram.   :thumbsup: but why is the second rh socket (old) still in the loop?

 

wouldn't that be eliminated?   :???:

 

Bryce

 

the old plug is in the mix still because that is whats used to open and close the relay. 85/86 on a relay is the activation coil.   setting it up like this allows you t still use the factory headlight switch to control the headlights while still removing the load from the switch.

[gogmorgo]

 

 

why excatly will the harness cause the switch to burn out? Improper gauge wire?

The stock one?

 

Because it is of small gauge wire and runs through the switch. Lots of resistance in the circuit and the switch has the breaker in it.

This.

Also worth noting: my headlight switch didn't just burn out, IT SET ITSELF ON FIRE.

Quick reactions to put it out saved my MJ from burning to the ground. There are many instances of people not being so lucky.

[Pete M]

hence my new signature.  :thumbsup:  although pulling back the carpet is also important. :yes:

[Marine1Texas]

I did the upgrade years ago, however the only times the headlights come on is inspection time. last time I had to replace a bulb was before 2000.

[cruiser54]

hence my new signature.  :thumbsup:  although pulling back the carpet is also important. :yes:

Good one!!

 

The harness costs less than a headlight switch and is easier to install.

 

Plus, even stock headlight bulbs will shine 35% brighter.

[dustyinthedirt]

Thanks guys! Thats what i figured caused but just wanted to double check.  :thumbsup:

[Megadan]

Be warned, as a side effect of that brighter shine, bulb lifespan is reduced somewhat.  Certain brands and types more than others.  I've had good luck with Sylvania Silver stars.

[Rockfrog]

Be warned, as a side effect of that brighter shine, bulb lifespan is reduced somewhat. Certain brands and types more than others. I've had good luck with Sylvania Silver stars.

How so, we are not increasing output over what the headlight was designed for, it's not shining brighter by General vehicle standards ... It's just finally seeing the 12V it was originally supposed to, and what most other vehicle supply. We're not making it so a 35W bulb puts out 55W (by increasing voltage) we are making a 35W bulb that used to output 20W of light output, finally output closer to 35W, finally. And preventing fires in the process.

 

Sent from my SGH-I337M using Tapatalk

[cruiser54]

 

Be warned, as a side effect of that brighter shine, bulb lifespan is reduced somewhat. Certain brands and types more than others. I've had good luck with Sylvania Silver stars.

How so, we are not increasing output over what the headlight was designed for, it's not shining brighter by General vehicle standards ... It's just finally seeing the 12V it was originally supposed to, and what most other vehicle supply. We're not making it so a 35W bulb puts out 55W (by increasing voltage) we are making a 35W bulb that used to output 20W of light output, finally output closer to 35W, finally. And preventing fires in the process.

 

Sent from my SGH-I337M using Tapatalk

 

I agree with rockfrog. 

[gogmorgo]

I'm definitely convinced that even if it does reduce the life of the bulb, a couple extra bulbs over the life of the truck is definitely not a significant enough savings to risk burning down the truck...

[cruiser54]

I'm definitely convinced that even if it does reduce the life of the bulb, a couple extra bulbs over the life of the truck is definitely not a significant enough savings to risk burning down the truck...

I'm sure the bulbs are designed for 13.8 to 14.2 voltage. They were lucky to get 10.5 before the harness. Not even an issue. 

[Gene]

Hi everyone,

 

I think there is some truth to the shorter bulb life.

 

With the harness, the bulb will have its normal length of life.

 

When a bulb is run at lower voltage, it will last longer than its rated life. For example, house current is 120 V. Back in the days of incandescent bulbs, a "long life" bulb was actually a 130 V bulb. This would give longer life, but less light output.

 

I'm still going to go with the harness.

 

Gene

[HOrnbrod]

24VDC military incandescent bulbs last forever in a 12VDC vehicle. They're great for daytime running lights but useless when it gets dark.  :yes:

[Megadan]

 

 

Be warned, as a side effect of that brighter shine, bulb lifespan is reduced somewhat. Certain brands and types more than others. I've had good luck with Sylvania Silver stars.

How so, we are not increasing output over what the headlight was designed for, it's not shining brighter by General vehicle standards ... It's just finally seeing the 12V it was originally supposed to, and what most other vehicle supply. We're not making it so a 35W bulb puts out 55W (by increasing voltage) we are making a 35W bulb that used to output 20W of light output, finally output closer to 35W, finally. And preventing fires in the process.

 

Sent from my SGH-I337M using Tapatalk

 

I agree with rockfrog. 

 

Actually, if you test the power at the bulb, they are seeing nearly 14 volts (13.8 on mine).  Their ratings and lifespan are tested just below 12.  This increase in power to the bulbs makes them burn hotter, which makes them brighter.  They burn out quicker.  Seen it on my truck, and also had the same upgrade on my crown vic with the same results.  

 

A little basic math, lets say a 35W bulb is pulling 3 amps. at 11.8V it would be at 35.4W.  Take that same bulb and lets leave the amp draw at 3, at 13.8V it would be pushing 41.4W.  Feel free to nit pick my math or example here as I am sure it has a flaw or two.  I just wanted to emphasize that the bulbs seeing nearly 14 volts will make a difference.

 

I never said they burn out regularly, but they do burn out quicker.   After 3 years the bulbs I installed with the harness and my new headlight housings finally burned out within 3 months of each other.

 

I want to reiterate a point I made before though.  The bulb brand and type makes a difference in the lifespan as well.  I ran Osram nightbreakers in my crown vic, the brightest bulb you can get.  They lasted 14 months.  I ran Silverstars, a lower output bulb, got about 4 years.

[HOrnbrod]

Get LEDs.

[Gene]

 

 

"A little basic math, lets say a 35W bulb is pulling 3 amps. at 11.8V it would be at 35.4W.  Take that same bulb and lets leave the amp draw at 3, at 13.8V it would be pushing 41.4W.  Feel free to nit pick my math or example here as I am sure it has a flaw or two.  I just wanted to emphasize that the bulbs seeing nearly 14 volts will make a difference."

 

 

So...at the risk of being a nitpicker....

 

Amps=volts/resistance           I=V/R

 

Resistance stays the same. If voltage changes, then current changes.

 

Let's round your numbers, make the bulb 36 watts, and the voltages 12 and 14.

 

At 12 volts,  3 amps flowing makes 36 watts.

 

So the resistance (ohms) is 12/3 or 4 ohms.

 

Now increase the voltage to 14. The ohms stay the same at 4.

 

So now the current is 14/4 or 3.5 amps

 

And the new watts are 14 X 3.5 = 49 watts

 

When I'm not sure about is whether the wattage is calculated at 12 V, or at a higher voltage. Since automotive electric systems actually run at about 13.5 V, I suspect (just a guess) that the wattage of 12 volt bulbs is actually calculated at 13.5 V. But I don't know that.

 

Hope this helps, and is not just totally confusing.

 

Gene

 

 

 

 

 

 

[Rockfrog]

I stopped using the higher wattage bulbs (55/65W silverstar ultras and Night runners and such) as I rarely saw over a years lifespan from them. I generally run the run of the mill halogen replacements these days, and can't remember the last time I replaced a bulb, current ones came with my truck when I bought it. And with the relay harness I rarely use hi-beam, usually only ever use it on logging roads.

 

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[Megadan]

 

"A little basic math, lets say a 35W bulb is pulling 3 amps. at 11.8V it would be at 35.4W.  Take that same bulb and lets leave the amp draw at 3, at 13.8V it would be pushing 41.4W.  Feel free to nit pick my math or example here as I am sure it has a flaw or two.  I just wanted to emphasize that the bulbs seeing nearly 14 volts will make a difference."

 

 

So...at the risk of being a nitpicker....

 

Amps=volts/resistance           I=V/R

 

Resistance stays the same. If voltage changes, then current changes.

 

Let's round your numbers, make the bulb 36 watts, and the voltages 12 and 14.

 

At 12 volts,  3 amps flowing makes 36 watts.

 

So the resistance (ohms) is 12/3 or 4 ohms.

 

Now increase the voltage to 14. The ohms stay the same at 4.

 

So now the current is 14/4 or 3.5 amps

 

And the new watts are 14 X 3.5 = 49 watts

 

When I'm not sure about is whether the wattage is calculated at 12 V, or at a higher voltage. Since automotive electric systems actually run at about 13.5 V, I suspect (just a guess) that the wattage of 12 volt bulbs is actually calculated at 13.5 V. But I don't know that.

 

Hope this helps, and is not just totally confusing.

 

Gene

 

 

 

 

 

 

 

put more power through a circuit with the same resistance and what normally happens?

 

Also, automotive systems generally run at 13.5-13.8V yes, but almost all vehicles on the road with halogen bulbs are lucky to see even 12 volts at the bulb.  My Crown vic stock had a spectacular 11.4 volts.   My Comanche was even more pathetic at 10.7.   That's the main reason these harness upgrades work so well, they provide a true connection to the main power source.

 

Also, most headlights state their wattage at 12V nominal, and will sometimes list a wattage rating at 13.2V (or similar max)

 

 

I stopped using the higher wattage bulbs (55/65W silverstar ultras and Night runners and such) as I rarely saw over a years lifespan from them. I generally run the run of the mill halogen replacements these days, and can't remember the last time I replaced a bulb, current ones came with my truck when I bought it. And with the relay harness I rarely use hi-beam, usually only ever use it on logging roads.

 

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The funny thing is, I ran the same Nightbreaker bulbs (same type and everything)  in another vehicle without failure for nearly 3 years.  I didn't have a harness upgrade in that vehicle.

[Rockfrog]

I actually stopped using them back in my YJ days ... Was a 92 YJ with the stock lighting system, so basicly the same as our MJ's.

 

I'm not arguing your math, your point is totally valid ... just passing along my experiences.

 

Hell most of my past needs to swap bulbs has been due to winter driving and the fist sized gravel used on our highways. Went through four bulbs on my XJ in one month, and a windshield as well.

 

 

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[johnj92131]

Generally, higher output lamps have a shorter lifespan.  I found SilverStars burned out quickly.  Run any 12 volt lamp at higher voltage and it will have a shorter life and more light output.

 

I recently installed a pair of Truck Lite LED lamps, just like what Don has had for several years.  The work GREAT.  And they are just as good at night as my Hella E-Codes with a relay harness on my Passat.  The TruckLite LED's performed very well on my recent 6500 mile cross country trip.  I paid $250 for the pair and it was money very well spent.

 

This is the best lighting solution for the Comanche!  If you can scrape together the $, then go directly to these and you too will be happy.

[cruiser54]

I have installed over 7 of these supplemental harnesses with nary a bulb failure.

 

Even with 80/100s in my 90 MJ.