Fanfare Horn / Rear Window Heating Relay. Porsche 964 1989–94 / 968 1992–95  ›  92861520301

The Genuine Porsche Fanfare Horn / Rear Window Heating Relay is an electrical switching component used in selected classic Porsche models to control a higher-current electrical circuit from a lower-current control signal.

Fits:

• Porsche 964 (911) C2 1989-93
• Porsche 964 (911) C4 1989-93
• Porsche 964 (911) RS 3.6L 1991-93
• Porsche 964 (911) RS 3.8L 1991-93
• Porsche 964 (911) TURBO 3.3L 1991-93
• Porsche 964 (911) TURBO 3.6L 1991-93
• Porsche 968 3.0L 1992-94
• Porsche 968 Sport 3.0L 1994-95
• Porsche 968 CS 3.0L 1993-95
• Porsche 968 Turbo S 3.0L 1993-94  

The relay allows the electrical system to supply the current required by the horn or heated rear window without routing the full operating current through the dashboard switch.

What This Product Does:

• Electrically switches a higher-current circuit using a lower-current control signal.
• Provides power to the relevant horn or rear-window-heating circuit.
• Helps protect switches and control wiring from carrying excessive electrical current.
• Allows reliable operation of the connected electrical component.
• Provides electrical isolation between the control circuit and load circuit.
• Replaces an original relay with burnt, worn or intermittent contacts.
• Helps restore factory electrical operation in classic Porsche models.

When used for rear window heating, the relay supplies electrical power to the heated rear glass when the system is activated. Porsche cataloguing specifically identifies 92861520301 as the rear-window-heating/defroster relay on several applications.

When used as the fanfare relay, the relay switches power to the horn circuit when the horn control is operated. The Porsche 964 central electrical diagram lists 92861520301 at relay position R23 as the fanfare relay.

Symptoms Of Wear Or Failure:
Because the same relay can perform different functions depending on the vehicle, symptoms vary according to where it is fitted.

Possible symptoms include:

• Horn failing to operate.
• Horn working only intermittently.
• Delayed horn operation.
• Horn operating only after repeated use of the switch.
• Rear window heater failing to operate.
• Rear window taking much longer than normal to clear.
• Heated rear window working intermittently.
• Rear window heating cutting in and out unexpectedly.
• Relay clicking without the connected circuit operating.
• No audible relay click when the relevant switch is operated.
• Electrical function returning temporarily after the relay is moved or tapped.
• Burnt or discoloured relay terminals.
• Corrosion on electrical contacts.
• Signs of overheating around the relay or socket.
• Intermittent operation that worsens as the relay heats up.

A failed relay is not the only possible cause of these symptoms. Fuses, wiring, switches, earth connections, horn units and rear window heating elements should also be checked during diagnosis.

Why Replacement Matters:
Electrical relays contain internal contacts that open and close every time the circuit is operated.

Over years of service, these contacts can become:

• Burnt.
• Pitted.
• Oxidised.
• Contaminated.
• Mechanically worn.

Age and repeated heating cycles can also weaken the internal coil or switching mechanism.

Once the relay becomes unreliable, electrical power may no longer reach the connected component consistently.

Replacing a defective relay helps restore:

• Reliable horn operation.
• Correct rear window heating where applicable.
• Consistent electrical switching.
• Proper current delivery.
• Reliable operation of the associated circuit.
• Factory-style electrical functionality.