# How To: Make the trunk-mounted taillights function as brake lights



## sciphi (Aug 26, 2011)

For those of you who have more skills at wiring/electronics than I do (I can cobble a basic headlight harness and that's about it), what would it take to make the trunk-mounted taillights function as brake lights? We already have a dual-filament bulb in that location, same as the quarter-panel-mounted brake lights. I'd love to have additional brake lights with all the distracted drivers on the roads these days.


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## Ru5ty (Jun 20, 2012)

during the day i dont think that the licence plate light will have any effect considering that they are pointing down and are not pointed towards the car behind you, during the night they will be visible but then again they would be off when your foot is not on the brake, which means you could potentialy get a ticket because the police would not be abel to see your licence plate.


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## 4piecekit (Mar 17, 2011)

No, I believe sciphi s talking about the portion of our tail lights that are on the trunk lid. If you notice as you're backed up in front of a window, these lights aren't used as brake lights. I think it'd be a great feature to have with all the crazies driving around here. Each day I drive in rush hour is an experience.


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## spacedout (Dec 7, 2010)

also seems to be a large amount of cruzes getting rear ended, more lights might help with that.


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## sciphi (Aug 26, 2011)

Ru5ty said:


> during the day i dont think that the licence plate light will have any effect considering that they are pointing down and are not pointed towards the car behind you, during the night they will be visible but then again they would be off when your foot is not on the brake, which means you could potentialy get a ticket because the police would not be abel to see your licence plate.


Not the license plate lights in the chrome trunk garnish, the red taillights immediately left and right of the chrome garnish. Those could conceivably be used as additional brake lights. They already have a dual-filament bulb in place. 

Time to check other forums and see how they've done it. This is an old trick on some boards, but new to the N. American Cruze.


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## Ru5ty (Jun 20, 2012)

oh sorry i did not understand. im excited to see the results!


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## 70AARCUDA (Nov 14, 2010)

It would only take one additional wire, but it'd (obviously) have to be routed forward along the side of the trunk up to where the trunk hinge is and then back to the trunk-mounted LAMP on one side and then across to the other LAMP on the other side of the trunk. Of course, this assumes the lamp sockets are already wired to "accept" this additional wire (push-on, solder, etc.).

Ask ER for details.


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## sciphi (Aug 26, 2011)

Courtesy of ElantraClub dot com and the great folks over there who helped direct me to it, here is a writeup on the same thing done on the XD Elantra hatchback: DIY Project 88 

That's my inspiration. Given how our CHMSL (3rd/center brake light) is LED and shouldn't draw that much power, running two additional bulbs off it shouldn't be that big an issue. Well, at least to me. 

I'll have to yank off the trunk covering tomorrow and see if the bulb sockets already have the necessary socket.


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## Aussie (Sep 16, 2012)

Just checked my Holden CDX Diesel and while the globes have 2 elements they are only tail lights.


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## JHC828 (Oct 29, 2012)

I would also be very interested in doing this... Subscribing for the how-to write up.


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## XtremeRevolution (Jan 19, 2012)

Really looking forward to this. Stickied.


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## sciphi (Aug 26, 2011)

Turns out it's going to be a bit more complicated than running a few wires. 

Parts needed:
1. 3-wire connector for a 3057 bulb that will fit into a Cruze taillight.
2. Connector of some kind (probably a fusible link for safety reasons) for another wire. 
3. T-taps to tap off of existing brake light wires. 
4. Possibly some wire loom.
5. Probably something else I'm forgetting about. 

The good news is that the power wires share a common ground, so grounding is taken care of through the factory harness. I'm assuming factory grounds will be sufficient for 2 additional brake lights. 

The bad news is that it appears that each taillight is run off its own harness, so tapping into each side for power might be necessary to avoid overloading a single circuit. I have no issue with this, even though it does mean more connections are needed. 

Here's what is currently in the trunk-mounted taillights: 










Connector:










In the brake light:




























I believe the part number is ZFB-07066-UO.

Right-side taillight connector:










Left-side taillight connector and trunk wiring connector:



















A more global shot of the connectors:



















So, how would you electronics experts go about this differently than I would? I'm all ears, since electronics/electrical isn't a strong suit for me.


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## obermd (Mar 3, 2012)

I would strongly consider getting a set of the bulb connectors that are currently used in the actual brake lights and then wiring the second brake light in parallel to the first brake light on each side. Don't wire in series or one bulb out would take them both out.


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## sciphi (Aug 26, 2011)

obermd said:


> I would strongly consider getting a set of the bulb connectors that are currently used in the actual brake lights and then wiring the second brake light in parallel to the first brake light on each side. Don't wire in series or one bulb out would take them both out.


I thought that's what I indicated. I could have been mistaken, in which case I'll edit my post. 

Looking on a GM parts website, the 3-wire connector is not available by itself. So a generic connector will need to be used and wired up. Not a big deal.


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## 70AARCUDA (Nov 14, 2010)

...FWIW, there's a "*trick*" way to '*splice*' into an existing wire _without_ having to cut through or remove the existing insulation. Simply solder the "new" wire to the 'head' end of a sewing *straight pin* and then push the point of the pin into the existing wire, parallel with the inside wire (do not push the pin thru from side to side so it makes a cross), and then wrap/seal the spot with some decent, long-life, electrical, weather-proof tape.


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## perlionex (Mar 10, 2011)

I believe that this additional set of lights are used at the rear foglights for my Asian Cruze. Do you guys have rear foglights over there?


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## sciphi (Aug 26, 2011)

No rear fogs on North American cars. US DOT regulations frown on rear fogs, so we don't get them. Canada doesn't get them either since their Cruzes are supplied from Lordstown, Ohio, and their regulations are pretty similar to US regulations. It's why US-spec Cruzes have daytime running lights even though DOT regulations leave them optional.

Also, most drivers over here are idiots, and would leave the rear fogs on even during clear weather. The number of cars driving around with foglights on during clear weather is staggering.


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## UpstateNYBill (Jan 14, 2012)

perlionex said:


> I believe that this additional set of lights are used at the rear foglights for my Asian Cruze. Do you guys have rear foglights over there?


No, we do not. A few foreign vehicles sold in the U.S. have rear foglights, but no domestic vehicles that I am aware of have them.


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## bryanakron40 (Nov 8, 2012)

70AARCUDA said:


> ...FWIW, there's a "*trick*" way to '*splice*' into an existing wire _without_ having to cut through or remove the existing insulation. Simply solder the "new" wire to the 'head' end of a sewing *straight pin* and then push the point of the pin into the existing wire, parallel with the inside wire (do not push the pin thru from side to side so it makes a cross), and then wrap/seal the spot with some decent, long-life, electrical, weather-proof tape.


Maybe it works, but I don't like the sound of it. I see it being a site of resistance and causing issues for both bulbs. Just my take on it.
You could use the older style weather pack connectors and terminals. I get them at Summit Racing. No they are not compact but are cheap and easy to find. You can get them in smaller packs, not just a kit like this.


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## Pete in PA (Dec 1, 2012)

Why is there a dual fillament bulb there if it's only a tail light?????


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## obermd (Mar 3, 2012)

sciphi said:


> No rear fogs on North American cars. US DOT regulations frown on rear fogs, so we don't get them. Canada doesn't get them either since their Cruzes are supplied from Lordstown, Ohio, and their regulations are pretty similar to US regulations. It's why US-spec Cruzes have daytime running lights even though DOT regulations leave them optional.
> 
> Also, most drivers over here are idiots, and would leave the rear fogs on even during clear weather. The number of cars driving around with foglights on during clear weather is staggering.


I turn my front fogs on when it gets dark. When properly adjusted, they really help close in wide angle vision, which has saved my bacon on more than on occasion by allowing me to see large animals running towards the road before I hit them.


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## sciphi (Aug 26, 2011)

The headlights should cover the side lighting without need for front fogs. The OEM bulbs are okay for distance, and not so hot for side throw. Swap in a set of different non-tinted bulbs, preferably Philips. The Sylvania XtraVision bulbs are great for distance and awful for side lighting. The Philips bulbs in my Cruze are good for distance and acceptable for side lighting. 

This project is on the back burner right now. I'll look at it again in the spring when it's warm enough to work outside comfortably.


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## GoldenCruze (Dec 18, 2011)

I was behind a Cruze tonight and thought about this thread while looking at the tail lights on it.

The tail lights on the Cruze are huge compared to most other cars. And I would rather have the trunk lights stay just as they are. I noticed that the difference in brightness helps me to more quickly identify that the brake lights are on. And I think it works that way for most other drivers as well. So I'm not about to make trunk lights function as brake lights.

And I noticed that the third brake light is dim by comparison. I'd like that one to be equally bright as the other brake lights. That's a change that I would make.


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## Wyre (Jul 23, 2011)

UpstateNYBill said:


> No, we do not. A few foreign vehicles sold in the U.S. have rear foglights, but no domestic vehicles that I am aware of have them.


My 2002 Oldsmobile Aurora had rear fog lights.... It was US spec


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## Blue_RS (Aug 30, 2013)

So has anyone successfully done this? Ive got the brake light sockets to fit in the trunk tail lights. How do you run the red wire or extra wire for the brake light signal?


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## Cruzncannada (Nov 21, 2015)

It should be pretty straight forward to run power from your third brake light in parallel, and if you can find the power wire for the trunk lights in the trunk the wire would be a minimum distance. 

Shouldn't running this from your third to the existing power wire provide enough extra power to brake light? I'll see if I have any of these at work next week (off for a week) and give it a try.


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## NickD (Dec 10, 2011)

Ha, also thought about it, a dual filament bulb in a single element socket. Brake filament draws 2.3 amperes, times two an extra 4.6 amps, can the circuitry handle double the brake current? Feel it should if you can hang a trailer on this thing, but not sure if you can do both. This would be three times the current. 

Here is the circuit, not a simple switch like the good old days, buried in that way over priced BCM.

View attachment 178953


Besides the Cruze also has that mandatory center brake light and is DOT approved. So just said screw it. Ha, my latest trick is when someone is following me half way up my exhaust pipe, switch on the hazards. 

Its not that I drive like a grandpa, have a thousand vehicles ahead of me that are driving slow. Like to give the guy ahead a couple of feet just in case he slams on his brakes.


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## JDH (Dec 24, 2014)

Pete in PA said:


> Why is there a dual fillament bulb there if it's only a tail light?????



Logistics. It is cheaper and more efficient on the assembly line to have one container of bulbs to pick from than to have a container of dual next to a container of single.


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## NickD (Dec 10, 2011)

Ha, on that rectangular four head lamp system inners had two prongs for bright only, outers had three with both bright or dims.

Plugging in the three prong headlamp into the inners would just switch on the brights, so just used those. If the dims on the outside burnt out, had a spare head lamp to use. Dims would always burn out first.

Here's a stupid question if one of those trunk lid tail lamps burn out, will you get a traffic ticket? Trunk liner is nice, but also a PITA to change that bulb.

First time I removed the outer ones, darn near needed a tow truck to pull that sucker out. That rubber grommet was really tight. No need for that, opened it up a tad with a drill can coated it with silicone grease. Sure doesn't rattle, still kind of tight, but not that tight.


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## ChevyGuy (Dec 13, 2014)

JDH said:


> Logistics. It is cheaper and more efficient on the assembly line to have one container of bulbs to pick from than to have a container of dual next to a container of single.


If there's an equivalent taillight-only bulb, I haven't seen it. I doubt if a custom order bulb type is going to save money.


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## JDH (Dec 24, 2014)

ChevyGuy said:


> If there's an equivalent taillight-only bulb, I haven't seen it. I doubt if a custom order bulb type is going to save money.



The question asked was why use a double filament bulb when only one is needed. May I suggest you check out a 3156 or the GM part #9442003


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## ssnscruzeeco2015 (Dec 29, 2014)

If you have access to the wire harness up far enough that the has all of the associated wires are in the same bundle, I should be a simple as the splicing in a pair of current control diode arrangements.

I suspect that each bulb has a separate wire leading from the BCM, but I am confident that you don't want the park lights to activate the brake lights.

Anybody happen to have access to the electrical diagrams?

Am I right in believing that the BCM will only flag a no current condition, to indicate a blown bulb, and that a slight change in current will not be flagged?

BTW firetrucks, and other emergency vehicles get rearended too. and they have about 1000 watts of flashing light running, and the excuses are endless.


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## StudentDriver (Mar 14, 2015)

I actually did this. Because the standard socket does not have a wire for the second filament(which is actually the running light filament, vs the high power filament), I ran a wire from the original wiring harness in the trunk up to the trunk lights. Now those act as my brake lights, while I ran the turn signal wire to my outer lights high power with a resistor. The outer lights remain the running lights, while the trunk lights are now brake only.


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