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Adding a Third Brake Light

Pelican Technical Article:

Adding a Third Brake Light

John Nelson






10mm socket/driver, wrench, 18 gauge wire (2 colors), Philips screwdriver, duct tape

Applicable Models:

Porsche 911 (1965-89)
Porsche 912 (1965-69)
Porsche 928 (1978-91)
Porsche 928 GT (1990-91)
Porsche 928 GTS (1993-95)
Porsche 928 S4 (1987-89)
Porsche 928S (1983-86)
Porsche 930 Turbo (1976-89)
Porsche 944 (1983-89)
Porsche 944 S2 (1989-91)
Porsche 944 Turbo (1986-89)
Porsche 944S (1987-88)

Parts Required:

Third brake light assembly

Hot Tip:

Get a buddy to help spot the location of the third brake light.

Performance Gain:

Better brake light visibility

Complementary Modification:

Check other brake lights
Editor's Note:  This article was written for the early 944s, but the techniques and wiring described here can easily be adapted to the 911 and 928 as well.


   Awhile back when visiting Michigan I was rear ended (my other car). The police ticketed her. I called my insurance company (SafeCo) and they said that because my damage was below my deductible, I'd have to collect myself... I called her company and they said "Sue us..." This put me at a disadvantage as I live in Illinois and was only visiting Michigan. (I'm a scoutmaster, and once a year we camp for a week in Michigan, it was during a trip to Wal-Mart that the teenage girl hit me) I would have to sue in Michigan.

   It was a big hassle and took months before I got paid. Since all the aggravation of the last rear-ending, I've been trying to protect myself from getting hit again. (My brother says I'm psychologically scarred and I should sue... ;-)

   One way I thought to protect my 944 was to add a third brake light. It's not required by law for a 1983 car, but with the low profile of the car, it just might save my behind someday.

Parts required:

1) Porsche third brake light assembly
Pelican Parts (PN# F-631-070-00) was $52.90 and is a Genuine Porsche part.

2) 18 gauge wire (2 different colors)
A 3 color pack from Radio Shack (PN# 287-1226) was $4.49.
The spools were just about the right length, we had little left over.

3) 18 gauge wire quick connects
Radio Shack (PN# 640-3049) sells 8 connectors for $1.49 and they fit the Porsche light perfectly.

4) 10mm socket and driver, or wrench
(This was the size of the ground lug near the spare tire on my 83 944)

5) Small Philips screwdriver

6) Cloth measuring tape or a nonstretchable rope.
(To measure center of hatch)

7) A small amount of Duct Tape

The kit:

1) The light kit consists of three pieces:

  • a flange that mounts with double stick tape to the glass hatchback
  • the light assembly itself
  • 2 small Philips screws which holds the front of the light to the flange (the back interlocks).

2) Installing this is easiest done with 2 people, although one helper can roam in and out of the area at times and takes about an hour (unless you are inept like we are ;-), I think we spent 3 hours total, but we did other stuff too.

First, find where to position the light:

1) Tape the cloth measuring tape or non-stretchable rope across the back window. If using rope, trim each end so that rope exactly fits window. Remove tape or rope, fold in half and mark center. Put back on window so you can see marks from the inside. Put a few across so you'll have a visible line to see for placement.

2) Pop open your hatch. Climb in back-seat, and note space between hatch and light. Have your helper open and close the hatch. Determine where you can mount it and not have wires pinched when closed, yet have it high up enough that it is just about out of view in your rear view mirror. This is a judgment call. (I'll post a URL with pictures)

3) Have your helper stand by the spoiler and open and close the hatch while you test fit the entire assembly

4) Once you determine where to place the flange, remove the orange protective strips from the tape, and stick in place. Have your helper visually check position from the back before you press into place.

5) With your helper placing a hand and gently pushing from the outside, gently but firmly press against the flange until you can see that the tape is firmly pressed against the window. DON'T PUSH YOUR WINDOW OUT!

Next step is getting power to to the light:

1) Gently remove carpet snaps covering tail light assembly on both sides.

2) Remove entire lower carpet section from trunk. We left it inside for most of the job then we realized we are constantly moving this around...

3) Locate ground lug between spare tire and drivers side turn signal assembly (this is where you'll be attaching your ground wire)

4) Locate black turn signal assembly on drivers side.

5) Remove white thumbscrew from drivers side turn signal assembly (this holds the cover on)

6) Carefully remove cover (light bulbs will come out with cover, use caution not to break or damage any)

7) Gently remove metal plate/bulb holder from black plastic cover (there are 3 plastic tabs that hold the two parts together). Pry them gently.

8) Just to be sure, have your helper tap on the brake so you know which bulb is correct. Then you tap on the brake while your helper watches so you both know the right bulb (saves arguments later). P.S. It's the bulb closest to the spare tire.

9) Look at the back of your car, 2 wires must be run to the top of the hatchback. We chose to run 1 wire up each side thru the weatherstipping. The positive wire we ran up the drivers side as described below, the ground wire we ran up the passenger side as described below.

Positive Wire:

1) We ran the positive wire behind the drivers side wall carpet to the last opening in the side vents, then up into the hatch weather stripping. There, we pressed it under the weather stripping.

2) To get it past the hatch light, we first ran a fish wire down the 3rd vent opening until we could feel it in the fender flare well. The wire needs to be pulled out the 3rd vent hole and then worked over to the first hole.

3) Leaving at least 2 inches of spare wire, crimp quick connect lug at top of hatch. Wire will have to go through center of light, then bend at right angles to be in proper position for quick connects.

4) Place a small piece of duct tape inside vent on wire to prevent the wire from moving.

Ground Wire:

1) We chose to run the ground wire behind the passengers side wall carpet to the last opening in the side vents, then up into the hatch weather stripping. There, we pressed it under the weather stripping.

2) Remove the jack and run wire underneath to avoid snagging later. My car came with duct tape (factory installed ?) to keep the ground wires away from getting snagged by the jack.

3) Run a fish wire down the 3rd vent opening. The wire needs to be pulled out the 3rd vent hole and then worked over to the first hole.

4) Leaving at least 2 inches of spare wire, crimp quick connect lug at top of hatch.

5) Place a small piece of duct tape inside vent on wire to prevent the wire from moving.


1) Attach positive wire to lug on passengers side of 3rd light (You'll see that it touches the base of the bulb in the socket)

2) Attach ground wire to lug on drivers side of 3rd light.

3) Insert rear of light assembly into flange and use the two small phillips screws provided with light to secure front of light to flange.

4) Carefully loosen ground lug near spare tire. Your Radio Shack quick connect package came with 4 quick connects and 4 spade lug connecters. Attach one of the spade connectors to the wire and attach ground wire with the rest of the ground wires to the ground lug. Re-tighten using care not to over tighten or strip lug.

5) Taking care not to damage the wire, pull the quick connect terminal off the brake light on the drivers side tail light.

Here you have two choices:

A) Carefully remove quick connect with pliers, twist (actually, my  brother wanted to solder it, but it was a cold day and would have taken forever) old and new wire together and crimp one of the remaining quick connects from the Radioshack package onto the two wires. Reconnect.

B) Insert new positive wire into one end of the existing quick connect and bend wire at other end of quick connect. Reconnect.

Note: Realizing that the wire was old and might crack, we opted not to remove the quick connect and instead used option B for attaching the wire. It was not our first choice, but we were concerned about breaking the wire and not having the length to reconnect it.


  • Have your helper press on the brakes. Enjoy the glow....
  • Did it light up? Did you blow a fuse?

We installed mine on 12/18 and have had no problems with fuses.

  • I can barely see the 3rd light in the rearview mirror. One thing

     I was afraid of was that I'd get a red glow at night on the glass, but with the light attached directly to the window, there is no reflection.

     Mine is not perfectly straight, but very close... instead of asking my brother to stand outside the car, I should have looked myself... But it's not far off... (Now that I look at it again, I don't think anyone but me would notice the millimeter or so, I guess my brother did an ok job spotting afterall)

     On my 1983 944 there have been no problems with the new light. The 3rd brake light is the brightest light on the car and depending on the angle viewed at, is very large. A typical person driving a van or SUV might see a 6.5 inch long by 4 inch wide red light when you tap the brakes due to the angle of the light...

John Nelson
83 944na
(for a picture to see just how many kids we could fit in my 944)

Michael Van Bibber adds:

While I found John Nelson's article on adding a third brake light very informative, after installing one on my own car, I found a few shortcuts that may make it significantly easier to install, especially for one person.

The only other tools you will need are:

1.    A non-permanent felt tip marker
2.    A permanent marker
3.    A combination square
4.    2 Quick splice connectors

Positioning the light:

NOTE: All Measurements and markings are done on the OUTSIDE of the glass

1.    Measure across the top of the hatch glass (Hint -- it is 44 inches give or take a few fractions of an inch). If you have factory glass installed, the "Sekurit" logo on the glass is extremely close to center. The long side of the upside-down triangle should be a good starting point. Mark center with the PERMANENT marker

2.    The third brake light is 7 5/8th inches long -- take your combo-square and from the first mark and make another mark at 7 5/8th and connect the two center marks and you now have a centerline.

3.    Using the mounting plate (the thin part of the light with the adhesive on it) Line it up (adhesive side down) with the centerlines, again, on the outside of the glass & trace around it with your NON-PERMANENT marker.

4.    Step back and admire your handiwork--you now have an outline where the third brake light will go. If you need to adjust, wipe off the marker with a paper towel and some water and your centerline will remain.

5.    Once you have everything lined up the way you want, open the hatch, climb in, peel the orange tape off of the mounting plate, and apply, using your lines as a reference. (Same warning applies -- DO NOT push so hard you pop your glass)

WIRING: I elected to make all of the connections right at the drivers side tail light rather than run one wire down each side. My car is an 85.5, so if yours is earlier, you may have to adjust the following.

1. Cut two wires about 7 feet long -- I used red (Hot) and green (Ground) wire

2.    Now that your trim piece is attached, attach your wire connectors (from the original article) to the wires, then attach connectors to the third brake light again, as you are looking at the light, the hot wire attaches to the right hand connector.

3.    Feed the wires out of the notch in the third brake light, at this point I twisted the wires together and put about 6 inched of heat shrink around them (primarily for a finished look).

NOTE: On the 85.5, there is a trim piece that covers the sunroof assembly and the bolts for the hatch This piece comes off with 5 screws. If you don't have this piece (I understand some do, some do not), I recommend that you follow the original instructions in the article. However, if you do have this piece, wiring gets a lot easier.

4.    Remove the trim piece, also, undo the screws on the side panel so you can feed wires behind it.

5.    With the hatch OPEN, connect the third brake light to the mounting plate.

6.    Pull the wires semi-tight (leave a little slack), and secure to the headliner with a piece of electrical tape (just to temporarily hold it). Continue sticking the wire to the headliner with electrical tape until you get to the side panels. Tuck the wires behind the side panel.

7.    Route the wires, back towards the tail light. Once you have the wires in safely tucked behind trim panels, carpet etc, tighten down the side panel, and reattach the trim piece.

8.    Remove the cover from the tail light assembly. Disconnect the wiring harness , then remove the metal plate from the plastic cover.

9.    Trim your wires to length. Using your quick splice connectors, connect the hot wire to the black/red brake light wire, (Hint: it is the bulb centered on the metal plate) and connect the ground wire to the Brown wire (it should be right in the middle of the metal plate).

10.    Installation is the reverse of disassembly (Take that Haynes!)

11.    Start up your car and try it out.

Michael Van Bibber (AFJuvat)

Comments and Suggestions:
avri Comments: how do i adjust the reversing light in my 928 S 1983 model
July 26, 2011
  Followup from the Pelican Staff: Is it not working or coming on at the right time? The switch itself may be faulty. - Nick at Pelican Parts  

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Page last updated: Fri 2/23/2018 02:27:46 AM