Disclaimer: The content of this document relates to the Porsche 993 (911 1995 to1998). I am not a professional automotive technician, and some of the opinions expressed in this document are just that, opinions; therefore, please feel free to use this document at your own risk. Many times, a lot can be learned by simply watching qualified professionals work on your 993
Battery Not Charging - The 993, for some reason, lacks a voltmeter on the dash. It does include a battery light in the clock that is directly connected to the alternator. When illuminated, it indicates that the battery is not charging. My understanding is that the battery light is actually part of the charging system, and if the bulb is blown out, your alternator will not charge. For this reason, it may be advisable to note that the light illuminates when the ignition is first turned on before starting the engine, and to always check the bulb before digging deeper into an alternator not charging situation. I have never come across this issue; however, others suggest that if you have the clock out for servicing and run the vehicle, you will run your battery down.
Battery Status & Charging -- The 993 likes a fully charged battery with a voltage of 12.7 ~12.6 volts at rest after the engine has been just turned off and can creep down to as low as 12V over an extended sit with the alarm energized. The system voltage should be between 13.5 ~14.2V volts with the engine running. Any lower, and the alternator/voltage regulator are not doing their job; any higher, and the voltage regulator is not working properly, and the excessive voltage will start to fry electronic components. If the voltage when running is too low, and before looking too deeply for the root cause, make sure the alternator belt is tensioned properly, as discussed on this page, as it may be too loose and slipping.
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| Cigarette Lighter Adapter |
On occasion, I have accidentally left the dome lights on in the car overnight, necessitating the need for a battery charge. I had an inexpensive 1.5 amp float charger on hand and purchased a cigarette lighter adapter cord for use in the car. Now, on the occasions where a mishap results in a discharged battery, I simply plug the charger into the cigarette lighter, close the door on the 12-volt wire, lock the car; the dome lights go out; plug the charger into the wall, and in 4 hours the car starts right up. Since the charging rate is very slow, one need not worry about overheating the battery or additional venting. A premade cord can be purchased from Amazon or eBay. The nicer ones have a light on the plug that illuminates when the plug is securely connected to the lighter socket. The cigarette lighter socket on our cars is the older, slightly larger style, so to make a snug fit, some put a rubber band or electrical tape around the lighter plug, or one can make the neat solution discussed on this page.
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| Trickle Charger |
The advantage of using the unswitched, constant-on cigarette lighter socket over a direct attachment to the battery in the frunk is that one need not bother opening
and closing the frunk to attach or detach the charger. If one decides to use the battery-direct connection method, the frunk lid needs to be closed on the charger cord to extinguish the frunk courtesy light.
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| Direct Battery Attachment Adapter |
If one prefers to leave the frunk ajar when using a charger the lower latch capture lever needs to be pressed down with a screwdriver so the latch is in the locked position to extinguish the frunk light and the frunk release lever pulled before closing the frunk when done.
With the direct battery attachment method, it is best to use the adapter that comes with most chargers rather than the alligator clips, as the adapter provides a positive connection while the clips can inadvertently slip off and, when live, touch things they shouldn't.
Avoid damaging your car when attaching a float or trickle charger.
One issue to be aware of is that if you disconnect the car's battery to attach a float charger, a significant electrical spike and electrical noise occur when you disconnect the cable from the battery terminal. There is also a smaller spike and electrical noise created when reconnecting the battery. Doing this regularly can cause spikes and electrical noise to damage the car's controllers. Also, when the battery is in circuit, it acts like a noise and spike filter. For these reasons, I would not disconnect the battery when using a float or trickle charger. The charger can be attached directly to the battery clamps in the frunk or to the cigarette lighter in the cabin, as discussed above.
Turn signals & dead batteries: The 993, being of European origin, has a street parking “safety” feature where, if the turn signal is active, the marker lamp for that side of the car remains illuminated when the ignition key is removed. North American owners usually first encounter this feature when they go to start their 993 in the morning and the battery is dead. “It’s not a bug; it’s a feature!"
Battery Bummers: I read almost daily about cars with dead batteries. On the 993 the alternator, if running correctly, should produce enough current to run all the electrical accessories and still charge the battery. It may be helpful to get one of those eBay cigarette lighter plug voltmeters.
It should read a minimum of 12.6 volts or more for a good battery shortly after turning the engine off and from 13.5 to 14.2 volts or so with the engine running. A good test of battery capacity is to run your car and read the voltage at rest just a few moments after turning the ignition off then read the voltage after the battery has been sitting for four hours. If it has dropped below 12.4 volts and seems to try too hard to turn the engine over, your electrical system has some sort of parasitic electric drain going on, or the battery is a candidate for replacement. Overnight, a good battery can drift down to 12.5 Volts +/- due to the normal parasitic loads in the system with the car parked, the turn signals off, and the doors locked with the little light on the door flashing in single, not couplet, flashes every second or so. Also, I unplug the voltmeter from the constant-on stock lighter socket when I park my 993, even though it is unlikely to meaningfully contribute to the parasitic run-down rate of the battery.
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| Cigarette Ligher Volt Meter |
An alternative is to add a switched outlet to the dash, as I did, which provides a permanent home for a volt meter/USB outlet discussed on this page.
All conventional car batteries lose moisture from their cells as a product of the battery's electrolysis or simply through evaporation. Even conventional so-called maintenance-free batteries have cells that need servicing, and some can be pried open and checked; others do not allow this, but I am told they can be MacGyvered and filled, although it seems like a bit of an invasive process on YouTube. If you can check the fluid level in your battery occasionally and make sure it is full up to the fill indicator rings in the throat of each cell. Use distilled water for this purpose. For future reference, it may be advisable to look for a battery brand that allows topping off the cells next time your battery needs replacing.
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