For heating the rear window in hardtop and soft top, a relay is fitted. Relay 1 is always activated as a hardtop may be fitted (no hardtop detection). Relay 2 is only activated when the soft top is detected as closed.
This phase is started only after the first time the button for the rear window defogger is pressed after terminal 15 ON (see following table for duration).
This mode takes place with one third of the total power output of the rear window defogger (pulse/pause ratio = 40 seconds ON/80 seconds OFF). Cyclic switching is deactivated from terminal 15 OFF.
If the rear window does not remain clear during or after cyclic switching, the full power output can be resumed by pressing the button for the rear window defogger again. The reheating phase is again followed by cyclic switching.
Operating mode |
Thawing phase |
Cyclic switching |
Restart: |
|---|---|---|---|
Duration |
10 minutes (outside temperature ≥ -15°C) 17 minutes (outside temperature ≤ -15°C) |
30 minutes |
5 minutes |
Function indicator lamps |
ON |
OFF |
ON |
Undervoltage monitoring |
inactive |
active |
active |
Terminal 15 OFF and ON again during afterrunning period (sleep mode) |
As before terminal 15 OFF |
OFF |
As before terminal 15 OFF |
The charge balance can move into the negative zone when the vehicle electrical system is subject to high load at low engine speeds (<< 1500 rpm). For this reason, the relays for the rear window defogger are switched off if the voltage level drops or in the event of overvoltage (battery voltage > 16 Volts for 5 seconds). The rear window defogger is switched off if the system voltage measured at the operating unit/control unit falls below 11.4 V. The rear window defogger is switched on again when the system voltage exceeds 12.2 Volts. The threshold values must be applied for longer than 10 seconds (hysteresis).
Notes:
Switching off the relays when undervoltage/overvoltage is detected has no influence on the duration of the operating statuses (defrost phase, cyclic switching, restart).
The function light (LED) remains on while the relays are switched off in the event of undervoltage/overvoltage.
The rear window defogger is also switched off during engine start (K-bus telegram, terminal 50).
The heated mirrors are not activated simultaneously with the rear window defogger but rather separately.