Electrical

Parking and Stop Light Bulbs

#1
Changing the parking light bulbs is not easy! The assembly is held in place from inside the fender with 2 nuts against a metal clamp. You almost have to be double jointed to do it.

#2
Here are some tips for solving false messages about bulbs being out in your central warning system. Make sure you replace all light bulbs in pairs, different bulbs can trigger the warning system. Make sure the sockets dry, clean and corrosion free. (very important) Don't use bulbs from your local auto parts store. The listings in the books they have are usually wrong and may melt your tail lens. Get bulbs from the Porsche Dealer if you can. There is no Porsche dealer near me so I go to the BMW dealership and get tail lamp bulbs for an 1988 735i (E32) The stop lamps from the same car have also worked for me in my 928. Check the ground point for the tail lamps and make sure it's clean. If all else fails the check the Central Warning System control box. It's inside the foot rest on the driver side. It rarely goes bad but check the connectors for corrosion.

#3
One of the inherent "faults" of the 928 is the fact that the two rear side marker lights eat a lot of water from the rear tires and then corrode. The tail light bulb warning light comes on to let you know that one of your lights is out (be sure to check the license plate lights too). No big deal. Just find the one that's out and then take the bulb out, sandpaper all the metal pieces and re-install the bulb. Then find some water repelling silicone (etc.) type spray and water proof that darn light assembly! Of course, you really could have a bad bulb too!


#4
Two hours to replace a light bulb!
I really enjoy working on my car, but some things push the envelope of enjoyment.

"Tail Light" warning on instrument gauge. Right rear marker light is out. I gently whacked the lamp, but it did not illuminate this time. (Hey, it worked well the previous two times!) Armed with advice from the 928 Tips website, I waited until I had some time to spare and started the process of removing the lamp. The back of my owners manual gives pictorial guides for replacing most light bulbs, but not for this one! Now I know why. The lamp assembly is held in place by two nuts on the inside of the fender. Because of its proximity to the fuel tank filler neck, it's really hard to get in there to remove the nuts. If you are facing this task, these tips may help.

1. Remove the wheel. It's nice to have the extra elbow room.

2. Pull the fuel filler overflow/drain tube out of its holder at the bottom so that you can swing it out of the way. Be careful with the place at the top of the hose where it attaches to the rubber boot. Mine was cracked already, so I patched it up with some black RTV at the end of the job.

3. Spray some WD-40 on the studs that hold the lamp assembly in place, and try to clean them up a bit, especially the rearmost one. The front nut can easily be removed with an 8 mm socket or box-end wrench, but the rear one is too cramped to get a socket wrench onto it. I ended up putting my box-end on it and only being able to loosen it a quarter turn with each go. After 10 minutes of working on this nut I was finally able to spin it the rest of the way off with my fingers.

4. As you remove the metal U clamps, be mindful not to loose the flat washers. Use pliers to pull the spade connectors off of their lugs. (Don't yank on the wires themselves.) Mine were on there pretty tight.

5. With the lamp removed I was able to clean it well with soapy water and nylon brush. I also cleaned the studs and nuts with WD-40 to allow that pesky rear nut to be threaded on easily by hand.

6. The bulb does not unscrew to come out. To remove it you must press on the white plastic tab with one thumb while using the other hand to give a little pry on the large metal tab with a small screwdriver. Clean the contacts, replace the bulb (Osram 5007 BA15s), and snap it right back in.

7. When reinstalling the lamp assembly make sure the rubber gasket is pushed in neatly behind the lamp before you snug down the nuts.

Hopefully it's easier to change the other three lamps. With one burned out, the others are probably not far behind, so I should probably go ahead and do the rest of them.

Regards,

+Greg Nichols
Alexandria, Virginia
'87 928S4, 5-speed, Venice Blue Metallic



OK. Here's how Jim at 928 International responded when asked how to change the marker bulbs:

>From inside the fender - pull back the rubber boot there is
>a flat metal piece you depress and the socket comes out
>the back of the light.

So, is it really that easy? No need to remove the lamp assembly? For the right rear, I don't think so, because the fuel filler tube obstructs access, but I could be wrong. For the other three bulbs, I suspect that it is that easy.

+Greg


Just did this. It depends on whether it's the driver or passanger side.

Driver side is easy, but you have to know what to feel for. You may want to practice on the front side markers, where you can see what you're doing (if the belly pan's removed, as mine was). You should not have to unbolt anything except for the rear passenger side - all the others snap out without tools.

Lie on the ground behind the rear wheel. Reach up from under the car towards the marker and feel around. When you find the assembly you should feel a rectangular rubber boot over it with the wires coming in the top. Pry off the boot with you fingers. Now feel around on the assembly. In the center will be a circular collar where the bulb socket is. On the inside of the circular collar, towards the front of the car, is a wide, 1" vertical tab. If you squeeze the tab towards the rim of the circular collar the socket will unlatch and you can pivot the bulb socket out. The whole socket comes down to below the bumper and you can easily change the bulb. Then reach back up, put the rear edge of the socket back in the circular collar and pivot it forward for the tab to catch. Then push the rubber boot back on. That's it!

Once you've practiced on the easy side, you can do the passenger side (after all, you'll want to replace the bulbs in pairs to prevent false bulb warnings). I didn't have to remove the wheel, but I'm lazy. You can try the same trick of removing the boot and pressing the tab on the passenger side, but the fuel filler makes it very tight to get the socket out. If you can wiggle it out, great. Otherwise, first spray the the two nuts (8mm?) with WD40 (with boot on). Next, remove completely the nut and bracket on the forward side near the wheel. Then loosen, but do not remove, the rear nut with a wrench (if the WD40 is working you can spin it from then on with your fingers). Loosen it enough that the assembly can be pushed out far enough that the forward threaded post clears the side of the car (you may want to cover the post to prevent scratches). Slide the assembly forward so that the circular collar clears the gas filler tube. Then remove the rubber boot, press the tab and remove the socket. Not fully removing the rear nut makes it easier to put back.

John Marum
'87 S4 5 speed