Emergency Fresh-Air System, Basic Function - GF86.10-P-9901A

Model all (CAR) 

with code Z25 (Emergency fresh-air system) 

Overview 

This document contains information on:

• General 
• Function requirements 
• Function 
  • Selftest
  • Internal pressure monitoring of compressed-air reservoir
  • Output of fault messages
  • Activate emergency fresh-air system
    • Manual activation
    • Automatic activation
  • Trigger emergency fresh-air system
  • Deactivate irritant gas sensor

General 

The emergency fresh-air system supplies the vehicle interior for a limited time with fresh air via a compressed air cylinder and prevents at the same time the ingress of smoke or irritant gases by generating a slight overpressure.

Function requirements 

• Circuit 15 ON
• Emergency fresh-air system activated (only for trigger emergency fresh-air system)

Function 

Selftest 

When circuit 15 is switched on, the LED in the emergency fresh-air system button and the LED in the emergency fresh-air system/fire-extinguishing system activation button in the Guard operating unit light up for approx. t = 6 s. If the LEDs are still illuminated after expiration of this time, the fire extinguishing system and emergency fresh-air system control unit has recognized a fault and the emergency fresh-air system is not working. The warning buzzer is actuated and the a message is indicated in the instrument cluster.

Internal pressure monitoring of compressed-air reservoir 

The fire extinguishing system and emergency fresh-air system control unit permanently monitors the compressed air reservoir. For this purpose the fire extinguishing system and emergency fresh-air system control unit directly reads in the signals from the compressed air reservoir pressure sensor. If the compressed-air reservoir internal pressure drops below p = 250 bar, the fire extinguishing system and emergency fresh-air system control unit actuates the warning buzzer in the case of circuit 15 ON for t = 6 s. Simultaneously the LED in the emergency fresh air system button is permanently actuated and a message is displayed in the instrument cluster.

Output of fault messages 

A message is output by the instrument cluster in the event of a malfunction to indicate errors to the driver.

Activate emergency fresh-air system 

The emergency fresh-air system can be actuated manually via the emergency fresh-air system/fire extinguishing system activation button or automatically by evaluating the signals from the irritant gas sensor.

Actuation is performed in both cases via the emergency fresh-air system button.

Manual activation: 

When the emergency fresh-air system/fire extinguishing system activation button is actuated, the emergency fresh-air system is activated manually.

Automatic activation: 

An irritant gas sensor monitors the outside air of the front vehicle surroundings. The emergency fresh-air system is activated automatically, when the irritant gas composition in the outside air exceeds a certain threshold.

The LED in the emergency fresh-air system button starts to flash for approx. t = 6 s after a manual or automatic activation. The emergency fresh-air system/fire extinguishing system activation button directly actuates the LED. Parallel to this the warning buzzer is actuated. In this time, the emergency fresh-air system can be triggered by actuating the emergency fresh-air system button (at least t = 1.5 s).

After the emergency fresh-air system is activated manually or automatically, the "recirculated air" function is activated and the ventilation deactivated momentarily to prevent ingress of toxic gases into the vehicle interior.

The air recirculation function can be stopped at any time by actuating the air-recirculation mode button at the front air conditioning control panel.

Trigger emergency fresh-air system 

The emergency fresh-air system is triggered by actuating the emergency fresh-air system button (at least t = 1.5 s). The fire extinguishing system and emergency fresh-air system control unit actuates via the "Close vent flaps" relay the left vent flap actuator motor and the right vent flap actuator motor. The vent flaps are closed for a period of approx. t = 5 min.

To open the vent flaps after this time, the vent flap servo-motors are actuated via the vent flap relay by the emergency fresh-air system/fire extinguishing system activation button.

The emergency fresh-air system/fire extinguishing system activation button directly actuates the emergency fresh-air system compressed air reservoir pin pusher. A pressure regulator reduces the pressure from approx. 300 bar to approx. 10 bar. The compressed-air reservoir is opened and the air flows into the vehicle interior via a vent with muffler from an opening in the rear shelf.

The discharge of fresh air from the compressed-air reservoir cannot be interrupted. The compressed-air reservoir is empty after approx. t = 2 min. During this time a slight pressure is present in the passenger compartment. The air delivery capacity is approx. 800 l/min. The compressed-air reservoir with triggering unit must be replaced after triggering.

Deactivate irritant gas sensor 

The irritant gas sensor can be deactivated for a certain period, i. e. until circuit 15 is switched off. For this purpose, the emergency fresh-air system/fire-extinguishing system activation button must be permanently pressed for t = 5 s. When circuit 15 is switched on again, the irritant gas sensor is reactivated.

When the irritant gas sensor is deactivated a corresponding message is displayed in the instrument cluster.

When the windshield washer system is activated, the irritant gas sensor is deactivated temporarily to prevent false actuation by the cleaning agent. For this purpose, the signal for the actuation of the windshield washer system pump is directly read in by the irritant gas sensor.

	Function schematics
	Function schematic for emergency fresh-air system		PE86.10-P-2501-97A
	Component descriptions
	Fire extinguishing system and emergency fresh-air system control unit, component description	Model 223 with code Z25 (Emergency fresh-air system)	GF86.10-P-2119A
	Emergency fresh-air system compressed air reservoir, component description	Model 223 with code Z25 (Emergency fresh-air system)	GF86.10-P-2129A
	Emergency fresh-air system vent flap actuator motor, component description	Model 223 with code Z25 (Emergency fresh-air system)	GF86.10-P-2130A
	Irritant gas sensor, component description	Model 223 with code Z25 (Emergency fresh-air system)	GF86.10-P-2134A