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Heated rear seat

Heated rear seat




Rear seat heating is available as an option for the Saab 9-5. The rear seat is then fitted with two heating pads, one in each seat.

The heating is controlled manually and can only be turned on when the ignition is ON. The heating time is controlled by TWICE and depends on the exterior temperature.

Description of operation


When the switch (252R) for the heated rear seat is pressed, B+ is supplied to pin 9 in TWICE. TWICE grounds the relay for the heated rear seat via pin 52.

The relay trips and supplies B+ via fuse 10 to the heating pad in the rear seat and to the switch indicator.

The length of time the heating is active depends on the exterior temperature. TWICE receives information on the exterior temperature from SID via the bus.

The heating will be on for 5 minutes when the exterior temperature exceeds -5°C. This period will be longer if the exterior temperature is below -5°C and reaches its maximum at -14°C. The period can be programmed between 3-18 minutes but is normally set to 10 minutes.



TWICE turns off the heating while the starter motor is cranking (+15 ON, +54 OFF) to save the battery. Once the ignition key has returned from ST to ON, TWICE will turn on the heating again.

For safety reasons, the length of time it is off is maximized at 20 seconds so that the heating works even if +54 is missing in the event of a fault.

TWICE receives information on the ignition +54 from DICE via the bus. Ignition +15 is connected to pin 16 of TWICE.

Button and controls lighting

The switch for the heated rear seat is lit by a bulb powered from DICE (pin 49, rheostat level). This voltage supplies the buttons and controls, ashtray light and cigarette lighter. For further information see Group 3 DICE, Button illumination and lighting for controls.

Diagnostics

In the event of a fault in the relay control circuit, diagnostic trouble code B1130 is generated in TWICE. The diagnostic trouble code is generated if there is:


• An open circuit or short circuit to ground

• A short-circuit to B+.


No diagnostic trouble code is generated for voltages below 11V or during diagnostic communication. The control module output can be activated using the diagnostic tool.