DIY – 3rd Brake Light Spoiler fitting (long)
03-05-2004, 01:07 PM
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Racer
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DIY – 3rd Brake Light Spoiler fitting (long)
Hi all,
Thought I’d give you my recent experience of fitting a genuine 3rd brake light spoiler to a 91 C4 Coupe. This is the spoiler that fits externally across the top of the rear window and has an embedded LED array.
I had to fit this in order to meet New Zealand certification regulations, as the C4 is soon to depart the UK for warmer greener pastures.
Overall this job took about 5-6 hours and required the help of a friend.
I ordered a genuine part from Type 911, which arrived and unxepectedly turned out to be 2nd hand (buyers beware when ordering from this company) but it was in excellent condition and came with a bag containing all the fixture parts (all new and all genuine Porsche).
This spoiler comprises of an outer painted skin, and an inner black plastic mount which carries the led light array, the wiring, and a rubber seal which fits under the trailing edge of the roof.
Job 1: finding the brake light wire.
Well I thought this would be hard – and it is. The brake light wire runs into the engine bay through a large rubber grommet (on the right hand side) as part of the main wiring loom. This loom can be seen once rear parcel (speaker) shelf has been carefully removed.
I’d hoped that there would be an exposed connector, but after checking every nook and cranny and testing every available connector in the side cavities (very hard) I couldn’t find anything useful. So after an hour of searching and convinced that I didn’t want to cut into the harness, I decided to run a wire from the rear brake light cluster into the cabin.
After removing the rear light cover I found the correct wire to use (after disconnecting the battery), and cut and spliced in a new black wire using automotive electrical connectors and heat-shrink to protect (PS. please don’t solder into a car harnesses as it fractures over time). With some difficulty, this wire was then passed through the existing long rubber grommet (using a friends help and a torch) into the engine bay and then along the existing harness and into the cabin. If you thread it along the underside of the harness, it’s hardly noticeable.
Job 2: Getting the wire into the roof cavity.
The wire has to be provided up to the top-centre of the rear window. The best solution would be to pass the wire up into the roof using the C-pillars, but I couldn’t see an easy way to get the wire up there, as the gap a the bottom is tiny and at a difficult angle. So in the end it was threaded through a tiny hole in the lining under the window rubber and hidden all the way to the top, where it emerges again and threaded back through the lining to enter the roof cavity. Again, this wire is completely unnoticeable.
In order to access the roof cavity, Porsche provided a long zip in the headlining. This gives access to the sunroof motor (if fitted). To gain further access, some lightweight panels (held in with plastic screws) must be removed. Pull a little on the panel while unscrewing and they will fall out quite easily. Once removed it gives about 2 inches working space.
I used one of the Sunroof motor mounting bolts as an earth point for the second wire required. Then did some continuity tests to see that all was still working.
Job 3: Drilling the bodywork
Ok, this isn’t a nice job - get it wrong and you’re in for an expensive afternoon.
You need to drill a small hole (approx 5mm diameter) just underneath the roofline lip (the bit that dips in at the top of the window) exactly centre with the spoiler. This will be completely covered by the spoiler’s rubber seal, so it won’t be seen once fitted.
I taped over the area I wanted to drill using insulation tape, and using a 1mm drill bit made a pilot hole, then extended it to 5mm. Seal the edges of the hole using a rust preventing paint (like Hammerite) and let it dry for an hour or so.
I wanted to fit a protecting rubber grommet in the hole, so I found one that would take the two wires and had a 5mm outer diameter. Then with friends help (who will be whinging quite a lot by this stage), the wires were fed through the hole (being very careful not to stretch the fragile roof lining), and emerged in the outside world (after 15mins trying).
In order to fit the grommet, slide the grommet on, then tie a knot in the wire and get your friend to pull gently on the wires from the inside. The knot will force the grommet against the hole and you can then gently work it into the hole using a small screwdriver.
The outside connectors can now be crimped and heat-shrink sealed. I must note that we constantly tested the wire continuity at each stage to make sure it was all still working, and at this point it would be a good idea to connect up the LED light array and test that it all works when you press the brake pedal. If it blows fuse 19, you have a short somewhere and in my case it was a loose wire inside the LED array.
Good idea to feed and water your friend at this point to reduce the complaining.
Job 4: Fitting the spoiler.
Aligning and mounting the spoiler onto the glass requires two people. The two mounts are fairly small rectangular plates that glues to the surface of the glass with pre-applied sticky tape (with protective cover) and a threaded vertical post to which the spoiler is mounted. Two spring-steel Z plates fit in between to provide additional torsion when tightened down. At this point the Z plates are left out and the mounts are assembled onto the spoiler so we can get an alignment onto the screen.
Carefully clean the glass using isopropyl alcohol in the area that each mount will approximately sit. Then using a friend’s help (who’s complaining quite a lot by now due to lack of beer) – offer up the spoiler onto the glass – using pressure to push the spoiler (rubber) up into trailing edge of roof, and centrally aligning it all against the glass rubber. Then carefully mark the position of the mounts using permanent marker.
Remove the mounts from the spoiler and then remove the protective tape cover from the sticky mount, carefully press the stick surface to the correct mounting position on the glass. Using a friend’s help to press firmly from the inside, press a reasonable amount of pressure evenly onto the mount for about 90 seconds, taking care not to pop the glass out. Your friend inside should be able to see where the tape pressure is not even – if there are bubbles press till they go. Repeat for the other side. It’s a good idea to leave the mounts to cure against the glass now for a few hours, and don’t be tempted to tug at them to see if they have fixed. While waiting for them to cure the interior was reassembled.
Now – mount the spoiler onto the posts, align and carefully tighten up. I choose not to use the Z springs as it seems they didn’t really need to be used, and seem to make the spoiler sit too high.
Then I connect the two sets of wires, reconnected the battery and tested the result. All worked fine. The painted spoiler cover can now be pressed onto the mount, and you’re done – except for helping yourself to well earned a beer – or several
Ade
Thought I’d give you my recent experience of fitting a genuine 3rd brake light spoiler to a 91 C4 Coupe. This is the spoiler that fits externally across the top of the rear window and has an embedded LED array.
I had to fit this in order to meet New Zealand certification regulations, as the C4 is soon to depart the UK for warmer greener pastures.
Overall this job took about 5-6 hours and required the help of a friend.
I ordered a genuine part from Type 911, which arrived and unxepectedly turned out to be 2nd hand (buyers beware when ordering from this company) but it was in excellent condition and came with a bag containing all the fixture parts (all new and all genuine Porsche).
This spoiler comprises of an outer painted skin, and an inner black plastic mount which carries the led light array, the wiring, and a rubber seal which fits under the trailing edge of the roof.
Job 1: finding the brake light wire.
Well I thought this would be hard – and it is. The brake light wire runs into the engine bay through a large rubber grommet (on the right hand side) as part of the main wiring loom. This loom can be seen once rear parcel (speaker) shelf has been carefully removed.
I’d hoped that there would be an exposed connector, but after checking every nook and cranny and testing every available connector in the side cavities (very hard) I couldn’t find anything useful. So after an hour of searching and convinced that I didn’t want to cut into the harness, I decided to run a wire from the rear brake light cluster into the cabin.
After removing the rear light cover I found the correct wire to use (after disconnecting the battery), and cut and spliced in a new black wire using automotive electrical connectors and heat-shrink to protect (PS. please don’t solder into a car harnesses as it fractures over time). With some difficulty, this wire was then passed through the existing long rubber grommet (using a friends help and a torch) into the engine bay and then along the existing harness and into the cabin. If you thread it along the underside of the harness, it’s hardly noticeable.
Job 2: Getting the wire into the roof cavity.
The wire has to be provided up to the top-centre of the rear window. The best solution would be to pass the wire up into the roof using the C-pillars, but I couldn’t see an easy way to get the wire up there, as the gap a the bottom is tiny and at a difficult angle. So in the end it was threaded through a tiny hole in the lining under the window rubber and hidden all the way to the top, where it emerges again and threaded back through the lining to enter the roof cavity. Again, this wire is completely unnoticeable.
In order to access the roof cavity, Porsche provided a long zip in the headlining. This gives access to the sunroof motor (if fitted). To gain further access, some lightweight panels (held in with plastic screws) must be removed. Pull a little on the panel while unscrewing and they will fall out quite easily. Once removed it gives about 2 inches working space.
I used one of the Sunroof motor mounting bolts as an earth point for the second wire required. Then did some continuity tests to see that all was still working.
Job 3: Drilling the bodywork
Ok, this isn’t a nice job - get it wrong and you’re in for an expensive afternoon.
You need to drill a small hole (approx 5mm diameter) just underneath the roofline lip (the bit that dips in at the top of the window) exactly centre with the spoiler. This will be completely covered by the spoiler’s rubber seal, so it won’t be seen once fitted.
I taped over the area I wanted to drill using insulation tape, and using a 1mm drill bit made a pilot hole, then extended it to 5mm. Seal the edges of the hole using a rust preventing paint (like Hammerite) and let it dry for an hour or so.
I wanted to fit a protecting rubber grommet in the hole, so I found one that would take the two wires and had a 5mm outer diameter. Then with friends help (who will be whinging quite a lot by this stage), the wires were fed through the hole (being very careful not to stretch the fragile roof lining), and emerged in the outside world (after 15mins trying).
In order to fit the grommet, slide the grommet on, then tie a knot in the wire and get your friend to pull gently on the wires from the inside. The knot will force the grommet against the hole and you can then gently work it into the hole using a small screwdriver.
The outside connectors can now be crimped and heat-shrink sealed. I must note that we constantly tested the wire continuity at each stage to make sure it was all still working, and at this point it would be a good idea to connect up the LED light array and test that it all works when you press the brake pedal. If it blows fuse 19, you have a short somewhere and in my case it was a loose wire inside the LED array.
Good idea to feed and water your friend at this point to reduce the complaining.
Job 4: Fitting the spoiler.
Aligning and mounting the spoiler onto the glass requires two people. The two mounts are fairly small rectangular plates that glues to the surface of the glass with pre-applied sticky tape (with protective cover) and a threaded vertical post to which the spoiler is mounted. Two spring-steel Z plates fit in between to provide additional torsion when tightened down. At this point the Z plates are left out and the mounts are assembled onto the spoiler so we can get an alignment onto the screen.
Carefully clean the glass using isopropyl alcohol in the area that each mount will approximately sit. Then using a friend’s help (who’s complaining quite a lot by now due to lack of beer) – offer up the spoiler onto the glass – using pressure to push the spoiler (rubber) up into trailing edge of roof, and centrally aligning it all against the glass rubber. Then carefully mark the position of the mounts using permanent marker.
Remove the mounts from the spoiler and then remove the protective tape cover from the sticky mount, carefully press the stick surface to the correct mounting position on the glass. Using a friend’s help to press firmly from the inside, press a reasonable amount of pressure evenly onto the mount for about 90 seconds, taking care not to pop the glass out. Your friend inside should be able to see where the tape pressure is not even – if there are bubbles press till they go. Repeat for the other side. It’s a good idea to leave the mounts to cure against the glass now for a few hours, and don’t be tempted to tug at them to see if they have fixed. While waiting for them to cure the interior was reassembled.
Now – mount the spoiler onto the posts, align and carefully tighten up. I choose not to use the Z springs as it seems they didn’t really need to be used, and seem to make the spoiler sit too high.
Then I connect the two sets of wires, reconnected the battery and tested the result. All worked fine. The painted spoiler cover can now be pressed onto the mount, and you’re done – except for helping yourself to well earned a beer – or several
Ade
03-05-2004, 05:57 PM
#3
Three Wheelin'
Ade,
I've just bought the identical unit (from Design 911) and I think I convinced myself that the Z springs should be fitted ON TOP of the black plastic part, not underneath where they would, indeed, raise the spoiler off the glass. I would have imagined that the point of the springs was to exert pressure downwards to force the spoiler against the glass.
I've got to say that I was REALLY impressed with the engineering - compared to some of the aftermarket parts I've seen the Porsche item is really Rolls-Royce quality.
Best regards
Dave Wilkinson
I've just bought the identical unit (from Design 911) and I think I convinced myself that the Z springs should be fitted ON TOP of the black plastic part, not underneath where they would, indeed, raise the spoiler off the glass. I would have imagined that the point of the springs was to exert pressure downwards to force the spoiler against the glass.
I've got to say that I was REALLY impressed with the engineering - compared to some of the aftermarket parts I've seen the Porsche item is really Rolls-Royce quality.
Best regards
Dave Wilkinson
03-05-2004, 06:03 PM
#4
Three Wheelin'
OK - so I've sat looking at the Z springs and the threaded posts and the springs are shaped to mate with the bottom of the post base - so they MUST go underneath the spoiler. Ignore my previous ramblings.
Dave
Dave
03-06-2004, 01:33 PM
#5
Racer
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Join Date: Jun 2001
Location: New Zealand
Posts: 370
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Hi,
Dave: had the same problem trying to work out where the Z springs went - decided the same as you - that they fit into the bases perfectly, they really dont seem to be needed though. Agree with you on the quality - the spoiler is really well made. Where did you splice the stop light wire into the loom?
Kevin: Cheers - I'll take a look.
Ade
Dave: had the same problem trying to work out where the Z springs went - decided the same as you - that they fit into the bases perfectly, they really dont seem to be needed though. Agree with you on the quality - the spoiler is really well made. Where did you splice the stop light wire into the loom?
Kevin: Cheers - I'll take a look.
Ade
03-07-2004, 12:25 PM
#6
Three Wheelin'
Ade,
I decided to fit the Z springs since it seemed that they are the sole means of holding the spoiler away from the glass. Without them I felt the only way to hold the spoiler firm would be to tighten the nuts to put pressure on the glass - and I didn't care for that solution too much. With them fitted the spoiler sits about 1/4in away from the glass, (just) clears the rubber screen surround and is rock solid.
I was lucky with the wiring since my supplying dealer had already wired it (for another non-Porsche spoiler/brake light which was really naff) so I did'nt have to do it. They had taken a spur from the left hand brake light in the rear cluster and taken the wire up the C post into the roof and earther the other wire on the sunroof motor. The hole for the wire was made about an inch from the right hand top corner - and that fitted perfectly with the new spoiler. Just gotta get it sprayed now!!
Dave
'89 C4 (non-factory Turbo-look)
I decided to fit the Z springs since it seemed that they are the sole means of holding the spoiler away from the glass. Without them I felt the only way to hold the spoiler firm would be to tighten the nuts to put pressure on the glass - and I didn't care for that solution too much. With them fitted the spoiler sits about 1/4in away from the glass, (just) clears the rubber screen surround and is rock solid.
I was lucky with the wiring since my supplying dealer had already wired it (for another non-Porsche spoiler/brake light which was really naff) so I did'nt have to do it. They had taken a spur from the left hand brake light in the rear cluster and taken the wire up the C post into the roof and earther the other wire on the sunroof motor. The hole for the wire was made about an inch from the right hand top corner - and that fitted perfectly with the new spoiler. Just gotta get it sprayed now!!
Dave
'89 C4 (non-factory Turbo-look)
