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