Porsche 928 S4 – Owner’s Manual

 

Model Year

1987

 

 

 

 

 

 

 

 

Contents

 

 

 

 

 

 

 

 

 

 

 

From the “Porsche 928 S4 Owner’s Manual”, available from 928 Specialists.

 

928 S4 page

 

John Pirtle

 

 

 

 

 

 

 

 

Fuses and relays

 

A failure in the electrical system may be caused by a blown fuse or a faulty relay.

 

The central fuse/relay board is located in the passenger’s footwell and protected by a cover plate.

 

The use of the fuses and relays is shown in a list on the floor board.

 

Before replacing a fuse, turn off all electrical components and the ignition; remove the key.  Replacing a fuse or a relay with the engine running or the ignition on could cause electrical shock.

 

When replacing a fuse, do not hold fuse by its metal parts.  In case of a repeated short circuit, the new fuse will burn out again, causing possible injury.

 

If a fuse blows repeatedly, do not keep on replacing it.  The cause of the short circuit or overload must be found.  On no account should fuses be patched up with tin foil or wire as this may cause serious damage elsewhere in the electrical system.

 

 

To replace a fuse . . .

 

  1. Lift carpet in the passenger’s footwell and tilt up the protective cover plate from fuse/relay board.

 

  1. In a blown fuse, the metal strip has melted.  In order to replace the fuse, it must be pulled from the spring clamp.  The tool for doing this is located at the top left on the central electrical system.  If there is doubt, or, for example, in the dark, the fuse can be tested by inserting it at the test point on relay VIII.  If the fuse is defective, the diode in the relay does not light up.

 

  1. Carefully install new fuse.  Use only fuses with the same rating as replacements!

 

  1. Replace cover plate and carpeting.

 

It is advisable to always carry a few spare fuses in the car.

 

 

Relays

 

Under the fuses, there are relay boards attached for various electrical switching functions.  Testing and replacement of a defective relay should only be done by an authorized Porsche dealer.

 

The relay for the rear window wiper is located on the back left, under the tool plate, the time relay for the seat heater is located under the seat.

 

 

If you need a circuit diagram, your Porsche dealer will be glad to help you.

 

However, in order to avoid damage to the electrical installation, we recommend having all work, including the installation of electrical accessories, done by your Porsche dealer.

 

 

 

 

 

Battery – 12 Volt

 

The battery is located underneath the collapsible spare tire in the luggage compartment.  The battery is accessible after taking out the spare tire.

 

A replacement battery should always have the same rating as the original equipment battery.  Specifications are printed on the battery housing.

 

Before work is done on the electrical system, the battery must be disconnected to prevent short circuiting.  First disconnect the negative ground wire at body and then the positive cable.  To reconnect battery, reverse the procedure.

 

This precaution must also be taken before charging with a rapid charger, as the alternator may otherwise be damaged.


Disconnecting the battery while the engine is running will damage the alternator.  This also applies to cars equipped with a battery main switch.

 

Never drive the car with a disconnected battery as this will damage the alternator.

 

WARNING

  • Do not lay tools or other metal objects on the battery as they could cause a short circuit across the battery terminals.
  • Do not expose the battery to an open flame or electric spark.  Hydrogen gas generated by the battery is explosive.
  • Do not let battery acid come in contact with skin, eyes, fabric or painted surfaces.
  • If you get electrolyte, which is an acid, in your eyes or on skin, immediately rinse with cold water several minutes and call a doctor.
  • Spilled electrolyte must be rinsed off at once with a solution of water and baking soda to neutralize the acid and prevent damage to fabric and metal.

 

 

Checking the electrolyte fluid level

 

The electrolyte fluid level in your battery can be checked by unscrewing and opening the filler vent caps of each cell.  The fluid level should meet the indicator mark in each cell.  If necessary, top off with distilled water.

 

How often water must be added depends on operating conditions and on the time of year.  Generally, the electrolyte level must be checked more often in the summer than in the winter, and more often when driving long distances.

 

Only fill up to mark, otherwise the electrolyte will overflow when the battery is being charged and cause damage.

 

 

Battery care

 

  • Battery should be securely mounted.
  • Terminals and connections should be kept clean and properly tightened.  Corrosion can be prevented by coating terminals and connections with petroleum jelly or silicone spray.
  • Vent caps must be securely tightened to prevent spillage.

 

 

Winter operation

 

During the winter months, battery capacity tends to decrease as temperatures drop.  Additionally, more power is consumed while starting, and the headlights, heater, rear window defogger, etc., are used more frequently.  Curtail unnecessary power consumption, particularly in city traffic or when traveling short distances only.  Let your Porsche dealer test the battery’s capacity before winter sets in.  A well charged battery will not only prevent starting problems but will also live longer.

 

 

Battery charging

 

Automotive batteries lose their efficiency when not in use.  The charge available in your battery can be measured with a hydrometer.  We recommend that battery voltage be tested by your Porsche dealer who has the appropriate equipment.  If the car is not driven for prolonged periods, the battery must be charged at least every 6 weeks.  A discharged battery allows rapid formation of sulfates, leading to premature deterioration of the plates.

 

WARNING

  • Charge battery in a well ventilated area.  Keep away from open flame or electrical spark.  Do not smoke.  Hydrogen gas generated by the battery is explosive.

 

  • Electrolyte fluid that may spill during charging should be washed off with a solution of warm water and baking soda to neutralize the acid.

 

  • If you get electrolyte in your eyes or on your skin, immediately rinse with cold water for several minutes and call a doctor.

 

  • Never charge a frozen battery.  It may explode because of gas trapped in the ice.  Allow a frozen battery to thaw out first.

 

  • Never use a fast charger as a booster to start the engine.  This may seriously damage the vehicle’s electrical system and the charger.

 

  • Fast charging a battery is dangerous and should only be attempted by a competent mechanic with the proper equipment.

 

 

Slow battery charging

 

WARNING

Heed all warnings and follow instructions that come with your battery charger.

 

  • Disconnect battery cables and remove the battery.

 

  • All vent caps should be open.  If fluid level is low, it should be topped up to the full mark in each cell.

 

  • Connect charger cables.

 

Charger cables must be connected POSITIVE (+) to POSITIVE (+) and NEGATIVE (-) to NEGATIVE (-).

 

  • Do not connect or disconnect charger cables while charger is operating.

 

  • Switch on charger.

 

  • Normally, a battery should be charged at no more than 10 percent of its rated capacity.  Rated capacity of the battery in your vehicle is listed on the battery housing.

 

  • After charging, turn off charger and disconnect charger cables.  When the electrolyte fluid has stopped “bubbling” in the cells, close the vent caps.

 

  • Tighten the vent caps and reinstall battery.

 

 

 

 

Emergency starting with jumper cables

 

WARNING

  • Improper use of booster battery to start a vehicle may cause an explosion.

 

  • Lead-acid batteries generate explosive gases.  Keep sparks, flames and lighted cigarettes away from batteries.

 

  • Do not charge a frozen battery, thaw it out first.  Gas trapped in the ice may cause an explosion.

 

  • No attempt should be made to jump start any vehicle with a low electrolyte level in the battery.

 

  • Check electrolyte level of each cell.  If necessary, fill with distilled water to just above plates.

 

  • Make sure the voltage of both batteries is the same.

 

  • The capacity (Ah) of the booster battery should not be lower than that of the discharged battery.

 

  • Vehicle with discharged battery: turn off lights and accessories, remove key, move lever to N or P and set parking brake.

 

  • Vehicle with booster battery should not be running.  Disconnect ground cable.

 

  • Remove vent caps from booster battery and discharged battery.  Preferably lay a cloth over open vents to reduce explosion hazard.

 

 

How to use jumper cables

 

WARNING

  • To avoid serious personal injury and damage to the vehicle, heed all warnings and instructions of the jumper cable manufacturer.

 

  • Only jumper cables of adequate diameter cross-section and fitted with insulated crocodile clips should be used.

 

  • The jumper cables must be long enough so that neither vehicles nor cables touch another.

 

Improper hook-up of jumper cables can ruin the alternator.

 

 

Always connect POSITIVE (+) to POSITIVE (+), and NEGATIVE (-) to NEGATIVE (-).

 

  1. Connect clamp of plus-cable to positive (+) terminal of discharged battery.

 

  1. Connect clamp on opposite end of cable to positive (+) terminal of booster battery.

 

  1. Connect clamp of minus-cable to negative (-) terminal of booster battery.

 

  1. Connect clamp on opposite end of cable to a bare metal part of car with discharged battery.  Connect clamp as far away from battery as possible.

 

  1. Start engine in the usual many.  If engine fails to start, do not continue to crank but contact nearest workshop.

 

  1. With engine running, remove jumper cables from both cars in exact reverse order: Steps 4 through 1.

 

  1. Reconnect ground cable of booster battery.

 

Do not try to start car by pushing or towing.  Damage to the catalytic converter, the transmission, and/or other components of the car may result.

 

 

Start assist connecting points sequence

 

On right side of engine compartment you will find a positive (+) battery post (remote connection).

 

First connect clamp at end of positive (+) cable to the remote connection in the engine compartment.  Then connect clamp at other end of positive (+) cable to the positive (+) terminal of the booster battery.

 

Next connect clamp at end of negative (-) cable to the negative (-) terminal of the booster battery.  Then connect clamp at other end of negative (-) cable to the engine compartment strut rod.

 

Caution: The cable clamps must not contact each other, and the plus-cable leading to the positive (+) post must not contact any metal part of the car.

 

Caution: Do not try to start car by pushing or towing.  Damage to the catalytic converter and other components of the car may result.

 

 

 

 

 

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