Question about upgrading wire harness

[Klutch9]

I've seen a lot of talk about upgrading factory wire harnesses for headlights. The concept makes sense, since the thin-gauge factory wiring is often restrictive. Plus, some people run higher wattage bulbs and need a beefier harness. Makes perfect sense. But...

A lot of the harnesses I see plug into the end of, say, the factory bulb socket, extend about 9" or so, and have a bulb socket at the end. True, the harness itself DOES have thicker-gauge wiring, but if it's plugging into the factory thin-gauge wires, how does this help? I'm thinking of getting a harness, but I'm having trouble understanding this.

 

[The_Jeff]

Resistance is a matter of by-the-foot, so cutting most of the thin stuff out does help.

 

[Smokescreen]

These 9" harnesses are exactly what you think they are...a money grab. True harnesses replace a lot of the factory wiring with bigger gauge...not just a few inches. The good ones upgrade with relays and sometimes fuses as well. More often then not once you upgrade with a true harness you no longer need upgraded bulbs as the voltage drop has been minimized to near nothing.

http://www.danielsternlighting.com/tech/relays/relays.html is a good article.

 

[Klutch9]

Say I wanted to do my own upgrades, simply by hacking apart the factory harness and replacing with as much thick-gauge wiring as possible... Would that help a lot, even without additional fuses and relays? I have plenty of thick wire and a soldering gun, so this wouldn't be too hard.

 

[Hokiefyd]

Originally Posted By: Klutch9
A lot of the harnesses I see plug into the end of, say, the factory bulb socket, extend about 9" or so, and have a bulb socket at the end. True, the harness itself DOES have thicker-gauge wiring, but if it's plugging into the factory thin-gauge wires, how does this help? I'm thinking of getting a harness, but I'm having trouble understanding this.


That would not help. At the same time, you also don't have to cut out the factory harness.

What you want to do is use the factory harness as your "switch", as an input to a relay. Then the relay pulls current directly from the battery through thick-gauge wire straight to the bulbs.

Edit: from the Daniel Stern article linked prior:

Quote:
We will simply use the existing headlamp wires to switch the relays on and off, and let the relays do the big job of sending or interrupting current to the headlamps. We use relays with plenty of current carrying capacity, which enables us to use heavy-gauge wiring that also has plenty of current carrying capacity. This way, we can bring full current to the headlamps, with virtually no voltage drop, even if we choose to install power-hungry overwattage headlamp bulbs.


Don't cut anything out of your factory wiring harness! What's there is just fine for powering the relay.

 

[Garak]

Originally Posted By: Hokiefyd
Don't cut anything out of your factory wiring harness! What's there is just fine for powering the relay.


Exactly. There's just no need to run full current through twenty feet of headlight wiring when a relay would do the trick. On old Audis like my 1991, that's been a big problem. Any upgrades to the lighting system would often promptly overheat the wiring. For whatever reason, though, installing a relay would trigger the burned out headlight warning.

I think the old F-150 will get the relay treatment when I get the time to do so. It has a very basic system, and very easy to work on.

 

[sciphi]

Check the voltage drop on the headlights before spending money on the harness. Both our cars have negligible voltage drop to the headlight connectors on the stock wiring. Well, according to my $3 HF multimeter.

 

[Klutch9]

Originally Posted By: sciphi
Check the voltage drop on the headlights before spending money on the harness. Both our cars have negligible voltage drop to the headlight connectors on the stock wiring. Well, according to my $3 HF multimeter.


What do you define as negligible?

 

[Klutch9]

Well, after reading some positive reviews of someone else who had an aftermarket harness on his '05 Focus, I've decided to make my own harness. I've rewired an ignition system before, and installed an amp & subwoofer, so this can't be all that bad

I will be sure to post pics of my harness and give my impressions. I hope to complete it this weekend.

I will be using 12-gauge wire, 20-amp inline fuses, and SPDT relays (2 of them). All connections will be soldered, and I will also solder the crimp-on spade connections to the wires for added peace of mind. Everything will be covered with loom also.

 

[sciphi]

Originally Posted By: Klutch9
Originally Posted By: sciphi
Check the voltage drop on the headlights before spending money on the harness. Both our cars have negligible voltage drop to the headlight connectors on the stock wiring. Well, according to my $3 HF multimeter.


What do you define as negligible?


Negligible means 0.1 or 0.2 volts. If it was 0.5 volts or greater, then I'd be making a few harnesses.

Can you get some readings of voltage drop on the stock H4 connector and on the harness? Thanks!

 

[Hokiefyd]

Cool. I would still recommend doing this with the correct HB4 pigtails (or whatever your Focus uses for the bulbs). This can be done, and done well, without cutting any of the factory wiring.

 

[Klutch9]

Originally Posted By: sciphi
Originally Posted By: Klutch9
Originally Posted By: sciphi
Check the voltage drop on the headlights before spending money on the harness. Both our cars have negligible voltage drop to the headlight connectors on the stock wiring. Well, according to my $3 HF multimeter.


What do you define as negligible?


Negligible means 0.1 or 0.2 volts. If it was 0.5 volts or greater, then I'd be making a few harnesses.

Can you get some readings of voltage drop on the stock H4 connector and on the harness? Thanks!


I don't have a multimeter, but my dad does, and I'll be seeing him this weekend.

I went to the store after work today, and assembled a price list of everything I'd need to make my own harness, and honestly, it's only slightly less to make my own... I'm talking like only $15-$20 dollars I'd be saving, and that's with no-name brand relays. I'm strongly considering just buying a "suvlights" harness at this point, since they use Bosch relays and 12 gauge wire (fused too). Either way, I'll take some readings this weekend and report back with my voltage drop.

It's too bad... I love wiring stuff up. I've installed several stereo head units, an amp & subwoofer, rewired my last car's ignition, and many a surround sound system. I love doing custom installs! But I fear that in this case, I could pay about the same for a superior product if I just bought a pre-made one.

 

[MisterBen]

I measured my 2009 Tacoma, without the engine running. I was getting about .45v drop on the driver's headlight, and about .75-.8v drop on the passenger.

I've been pondering making a harness because of that.

 

[Klutch9]

UPDATE: So I bit the bullet and ordered an "Suvlights" heavy duty headlight harness last wednesday night. I priced everything out to make a harness myself, which I am capable of, and the price was so darn close to the suvlights one that I felt it wasn't worth going through all the trouble, plus the cost of gas going to multiple stores to get the supplies.

Has anyone bought from suvlights before, and, if so, how long did it take to get your order? I have heard that over the years, their customer service has improved quite a bit. However, I have yet to get a tracking number and it has been almost a week. I emailed them Monday afternoon regarding this; still no response. I'm not too worried, just wondering if anyone else has had an experience with this company.

 

[Hokiefyd]

I ordered one set of H13 Philips Vision Plus bulbs from them years ago, and threatened to call the credit card company and stop payment on them. I didn't receive the bulbs for a month. You said that you've heard that their customer service has improved, implying that it was once bad, and that would correlate with my experience from years ago. I don't have more recent experience with them to know if it's any better lately.

 

[sciphi]

I've heard their stuff is quality, and their customer service is the pits. That's based on years ago forum posts.

Hope your experience is better.

 

[Klutch9]

Originally Posted By: sciphi
I've heard their stuff is quality, and their customer service is the pits. That's based on years ago forum posts.

Hope your experience is better.


Funny thing is that most of the comments, reviews, etc. are all from years ago, namely the early/mid 2000's. There isn't much at all in the way of reviews, positive or negative, more recently. But what what I HAVE been able to gather, they have gotten better over the years. I just called a couple times; no answer. Hopefully I get them soon. I'm sure the product will be of good quality, and it's not like I'll die if I don't get it soon, but ya' gotta have good customer service

I'd even be happy if I called them and someone answered, "Hello, this Peggy". At least that would be something

They haven't answered my email yet either.

 

[sciphi]

Originally Posted By: Klutch9
Originally Posted By: sciphi
I've heard their stuff is quality, and their customer service is the pits. That's based on years ago forum posts.

Hope your experience is better.


Funny thing is that most of the comments, reviews, etc. are all from years ago, namely the early/mid 2000's. There isn't much at all in the way of reviews, positive or negative, more recently. But what what I HAVE been able to gather, they have gotten better over the years. I just called a couple times; no answer. Hopefully I get them soon. I'm sure the product will be of good quality, and it's not like I'll die if I don't get it soon, but ya' gotta have good customer service

I'd even be happy if I called them and someone answered, "Hello, this Peggy". At least that would be something

They haven't answered my email yet either.


Maybe the guy's not answering because he's so dedicated to building quality harnesses and yelling at suppliers for the lowest prices!

 

[Klutch9]

Originally Posted By: sciphi
Originally Posted By: Klutch9
Originally Posted By: sciphi
I've heard their stuff is quality, and their customer service is the pits. That's based on years ago forum posts.

Hope your experience is better.


Funny thing is that most of the comments, reviews, etc. are all from years ago, namely the early/mid 2000's. There isn't much at all in the way of reviews, positive or negative, more recently. But what what I HAVE been able to gather, they have gotten better over the years. I just called a couple times; no answer. Hopefully I get them soon. I'm sure the product will be of good quality, and it's not like I'll die if I don't get it soon, but ya' gotta have good customer service

I'd even be happy if I called them and someone answered, "Hello, this Peggy". At least that would be something

They haven't answered my email yet either.


Maybe the guy's not answering because he's so dedicated to building quality harnesses and yelling at suppliers for the lowest prices!



Well, considering that the voice recording for their number was made by a woman, I'm guessing there's more than one person working for the company. Haha.

 

[Ken2]

Originally Posted By: MisterBen
I measured my 2009 Tacoma, without the engine running. I was getting about .45v drop on the driver's headlight, and about .75-.8v drop on the passenger.

I've been pondering making a harness because of that.
Toyotas (as least mine) switch the negative wire, not the positive, for the headlights. That makes designing the wiring harness more challenging. I did it, but didn't keep a diagram.