Toyota Negative Switched Headlight Signal

[lonesouth]

I installed some aftermarket driving lights in my 4runner. When I was running the wires, I encountered the oddball circuit Toyota decided to use for their headlights. Instead of switching the positive leg of the headlight, toyota switches the negative side. This isn't unheard of, but it does present the problem of where to get a signal from the headlight in order to trigger the relay for the driving lights.

Ideally, the driving lights will be on only when the high beams are on. Additionally, a switch to turn them off would be nice. The stock headlight switch, when turned on, provides power to all the headlights fuses under the hood, regardless of the highbeam switch. I am not a fan of hacking factory wiring, so my hopes of using an add-a-fuse on the high beam fuse will not work for a relay signal.

My solution is to use an HID 9005/9006 pigtail.

Ebay Search

Then, I can splice into the negative side of the headlight without hacking the factory harness. This is not my ideal solution, it creates additional connections in the headlight circuit that can be failure points/increased resistance, but it is preferable to cutting the harness.

Please post back if you have used other solutions for this problem. I'm certain I am not the only one.

[Alaric Darconville]

Careful with some of those bargain-basement eBay products-- many of those pigtails are very poorly constructed extension cords. As you have noted, you'll have the additional connections which introduce their own losses, and you'll have wire of unknown quality in between them.

Another consideration is that it may be preferable that not only can the auxiliary high beams only be turned on when the headlight high beams are on, but will not automatically come on with the high beams, and, lastly, will extinguish (and stay off) when you dip the main beams. This may require some creative wiring, but it should be accomplishable by tapping into the "signal" side of relays, not the supply/load side.

Daniel Stern, of danielsternlighting.com may be the man to talk to; Scheinwerfermann may also be able to supply some insight.

[Lightdoctor]

Ever though of just buying a relayed headlight harness that is power switched that works off a Toyota negative switched system? I did this with my Tacoma and tapped the high beam positive lead of the new harness to power up the relays for the two sets of auxillary high beams. My truck uses the H4 lamp format...it's easier to find a Toyota compatible harness to fit this lamp. Bought mine from headlightservices.com...maybe they or Daniel Stern can make one up for you. BTW, you'll have brighter headlights too!

[Norm]

Toyota negative switched H4 headlight harness with relays
Norm

[lonesouth]

Alaric: I am going to try the cheap harness first, but I will have fuses on all of the hot legs. If it fails, I will pull the extension out and run without the aux lights. I am also researching a switch to control the lights independently, it looks like they made a fog light switch for the Tacoma that will work and looks good, but it is $40, so I'm not jumping into it yet. It will also require some more research and probing with the DMM to determine if there is an acceptable place to tap the signal to the high beam relay. Thus far, tapping the load ground is the best solution that I have found.

Lightdoctor, Norm: I didn't see a clear and final solution to your problem in that thread, hence this thread. Also, I am comfortable enough making my own harness, it was my job for a few years, I just didn't understand the Toyota system. It seems as though this is a common issue when dealing with negative switched systems and especially with Toyotas. That and I'm too cheap to buy something I can, should be able to, make myself. Plus, I get to learn more about my vehicle doing it myself, which I always count as a good thing.

[Alaric Darconville]

I suppose you could use cheapie premade stuff as a proof of concept, and then go with known quality high grade wire and ceramic sockets once you're done testing. Again, it'd be preferable to have an interlock with the high beam circuit to eliminate accidental auxiliary beam activation. Depending on where that accessory switch is, a curious passenger ("oh, hay!!1 what is this button do?") can cause an accidental activation.

[lonesouth]

Once I get the switch, it will go on the driver's side above the left knee in a currently blank slot. There are other switches there that have never been hit, by me or the wife, accidentally. It is a good point though; in my younger years, i would torment my brother's GF by hitting the hazard light switch in her beemer...

I'll report back on the extension install with some impact results. I.E. current change due to extension/relay.

[Wok]

Lonesouth,

This kit may be what you are looking for?
http://www.traxide.com.au/HL_info.html

eng hoe

[Qship1996]

Lonesouth,

This kit may be what you are looking for?
http://www.traxide.com.au/HL_info.html

eng hoe

No mention of actual wire gauges used, ceramic sockets, or name brand relays.....until those key questions are asked, I would pass on this kit

[lonesouth]

Got my china harness in yesterday. Yes, they are cheap, but for what I paid, it was exactly what I expected. In regards to ceramic sockets, the factory harness is not ceramic = no sleep lost. Also, my china socket did not match my factory socket, required a little bit of trimming on the keying to get it to fit. Another surprise is that the black wire, on the china harness is not the negative side of the circuit, the red wire is. I didn't break out the DMM, I'm just looking for proof of concept at this point. Once I have successfully spliced the red wire, and heat shrinked all my connections, the aux lights functioned as expected. Head lights on, low beam on, aux off. Headlights off, high beam on, aux off. Headlights on, high beam on, aux on. Again, I am just using the high beam ground side as the ground for my relay that powers the aux lights from the battery. The B+ is fused on both the lights and the relay tap. I did not notice a drop in light intensity or throw as a result of adding the additional harness/tap.

Also, I have about $10 in this setup and I know how it works. I know the joints are solid. If there is a failure, I know where to look. Much better, IMO, than spending $130 on a harness that I don't know anything about.

[Alaric Darconville]

Got my china harness in yesterday. Yes, they are cheap, but for what I paid, it was exactly what I expected. In regards to ceramic sockets, the factory harness is not ceramic = no sleep lost.

Well, as a proof of concept, it doesn't have to be super high quality, the assumption being that sooner rather than later you'll be replacing it with something better.

I did not notice a drop in light intensity or throw as a result of adding the additional harness/tap.

That doesn't necessarily mean that there isn't a drop in light intensity or throw, of course.

[lonesouth]

Indeed.

without a meter, it is difficult to ascertain the actual change in light.

Perception is that it did not change.

[Qship1996]

Gotta love that walmart mentality......purchase items solely on upfront low price as compared to true cost over the product lifetime and long term value for the dollar.Has fooled millions and millions of consumers.

[Alaric Darconville]

Gotta love that walmart mentality......purchase items solely on upfront low price as compared to true cost over the product lifetime and long term value for the dollar.Has fooled millions and millions of consumers.

What I'm getting from this (or maybe it's just projecting) is that he wanted something pre-made, fast and cheap, to see if the more expensive quality item would be worth the purchase, rather than running the risk that he'd put all the money up front only to learn that it won't work.

lonesouth: Please tell me you're going to upgrade to the "real deal" now that you know it works.

[Scheinwerfermann]

Perception is that it did not change.

Using what bulbs, exactly? And what were voltage readings across operating bulbs before/after?

[Alaric Darconville]

without a meter, it is difficult to ascertain the actual change in light.

Using what bulbs, exactly? And what were voltage readings across operating bulbs before/after?

True, you don't need a lightmeter to measure the change in output-- a voltmeter, used correctly, will work pretty well.