Q – I just got my 1992 Carrera 4 out for the summer and what a surprise. The taillights on the left side don’t work and I can see water inside them. The dome light fell out and it doesn’t work. I am also getting a “light show “on my dash.   Numerous warning lights are coming on at random as I drive the car. If I turn it off and then back on, they all work normally for a while. My radio is also dead. I had none of these problems when I stored it last fall. – Marc

A – Sounds like it is time to do some electrical spring cleaning. This is what makes keeping old cars such a treat.  There is always something to tinker with. Isn’t it great when you can actually fix things? Got a few hours to play with your Porsche? Let’s dig in.

The taillights on this model leak water and the contacts have probably corroded on the lighting sockets or in the plugs. First remove the assemblies and drain the water. Look for some white crusty residue or red rust on the sockets or around the terminals. That shmutz is the byproduct of galvanic corrosion and it is easily brushed off to make a good contact again unless it has rotted the contacts out of the socket. If the sockets have rotted beyond cleaning, bulbs can be “hard wired” to the harness, if you prefer to spend your cash on necessities. Since the sockets are not available as a separate part this is an economical and reliable repair. Once you clean everything, apply a thin layer of silicone dielectric grease to the areas that corroded.

Of course then there’s the issue of how did the water get into the taillight if it is not broken? The lenses are heat welded to the reflector and the weld has probably failed. If you can afford it, just replace them. The problem is, the new ones won’t match the color of the others since the red tends to fade and they become pink.   The other problem is the extreme cost of two new lights and the center taillight. So if you are industrious, you can try to reseal them. And if the reseal doesn’t work, I cover my bets by drilling three tiny drain holes in the bottom of the reflector so any water that gets in can also get out.   If the water can’t attack the metal, the taillights should be as reliable as they were for the first 17 years.

The dome light fell out of the roof since the plastic housing has warped from age and heat. It seems to happen to all Cabrios. If it works fine otherwise, you can increase tension on the little bullet shaped pins by adding some discretely placed layers of tape. I prefer narrow strips of blue or green masking tape. Don’t use electrical tape, duct tape, or scotch tape. It tends to get gooey.

As far as the dome light not working, I bet that the rubber boots for the dome light switches are rotted.  Look carefully. When water runs down the A-pillar, it seeps into the switch if the boot is torn. Once water seeps in, corrosion occurs at the contact point (which you can’t see) and the dome light switch fails to turn the light on. You can unscrew the switch, clean it with contact cleaner and a small brush then lubricate it with silicone grease. With a new boot, just like the taillights, you are good for years.

That light show on the dash can have numerous causes. When your battery goes dead, a number of things can happen if you jump the car. If the systems that are indicated actually function, worry less about the lights and take it in for a computer scan. This may reveal the source of the fault and it can also reset the computer to basic settings. On some Carreras I have found the ignition switch intermittently failing which will also cause this symptom (it is not a very expensive part.) Once your vehicle is reset / rebooted, it will begin learning your driving style to optimize fuel mixture, ignition timing, and POWER!

The radio fuse may have blown due to a power surge. If you can remove the radio, check the fuse on the back and replace it.  If you can’t see it blown, that doesn’t mean that it will pass current. Check it with a meter. Once the radio powers up, if it is in “code” or “safe” mode, it will need to be reset with your security code. If you have the code but don’t know how to reset it, pay a kid to do it, they are a lot smarter than us when it comes to electronics. Ask me, I have two teenagers.  –MC