57
The interfaces
The driving speed signal
(a square wave signal processed by the dash
panel insert, the frequency of which changes
analogously to the speed)
is required in the evaluation of the driving
condition (stationary/driving mode) and
thereby for the selection of the control
criteria (see ÒControl conceptÓ). 1 wheel revolution
Signal T.15 ...
... is used for the evaluation of the system
status, run-on, stationary, driving and sleep
modes.
Signal T. 50 ...
... signals the control of the starter and is
used to switch off the compressor during the
starting process.
If a low position is detected after a wake-up
pulse, the compressor is actuated
immediately in order to allow the vehicle to
drive off as quickly as possible.
The compressor is switched off during the
starting process to protect the battery and
ensure starting performance. The door switch signal...
... is an earth signal from the control unit for
central locking. It signals that the door or
boot lid/tailgate is open.
... serves as the Òwake-up pulseÓ for the
transition from sleep mode to run-on mode
(see ÒControl conceptÓ).
Driving speed signal (4 pulses)
Signal from speedometer sender (reed contact)
We speak of run-on mode even if the
system is currently in Òrun-upÓ mode
(after a wake-up pulse before
commencing driving).
198_069
61
Overheating protection
In order to protect the compressor from
overheating, it switches off at excess
temperatures.
A temperature module is integrated into the
control unit. This monitors the temperature
and is used to calculate the compressor
temperature.
The calculations are based on the running
and cooling times of the compressor.
The max. running time is limited to 120 sec.
(an fault entry is made in the control unit
whenever the maximum running time is
exceeded).
15 seconds running time are allowed
following every 6 minutes of cooling time.
After 48 minutes of cooling time the
maximum running time of 120 seconds is
available.
242_011
Battery protection
In order to protect the battery, the maximum
running time of the compressor is limited to
60 seconds after the ignition has been
switched ÒOFFÓ. The system switches off and
only reactivates after the ignition has been
switched ÒONÓ again.
Switching self-levelling on/off.
The system can be switched off using the
diagnostic tester, e.g. during repair work.
When the ignition is switched ÒONÓ, the
systemÕs off status is indicated by a ßashing
warning lamp (T34).
At a driving speed of >20 km/h the system is
activated automatically.
198_039242_085
