A/C Compressor Control
While the ignition is turned on, the BC1 outputs a compressor on/off request to the EMS2000 every 10 ± 0.1 seconds. When the ignition switch is first turned to position 2, the request is set to compressor off. When the engine is running and the AC switch is pressed, the BC1 illuminates the indicator LED in the switch and changes the request to compressor on.
When it detects the request has changed to compressor ON, the EMS2000 energizes the compressor clutch relay, located in the engine bay fusebox, to supply battery power to the compressor clutch.
After receiving a compressor ON request, the EMS2000 outputs a compressor clutch status message to the BC1 to advise if the request was granted or not. If the compressor ON request was granted, the BC1 keeps the indicator LED in the AC switch illuminated. If the compressor ON request was refused, the BC1 flashes the LED at 0.5 Hz and repeats the compressor ON request until it is granted or cancelled by:
- Pressing the AC switch again, which changes the request back to compressor OFF.
- Selecting the blower off, which changes the request back to compressor OFF.
- Selecting the ignition switch to 0.
Once the compressor ON request is granted the LED in the switch remains illuminated until the request is cancelled or the engine stops, even if one of the grant conditions no longer exists. If one of the grant conditions no longer exists, the EMS2000 de-energizes the compressor clutch relay, to disengage the compressor clutch, until the grant condition is restored.
Hard acceleration can cause the compressor clutch to be disengaged. After three occurrences in a single ignition cycle the EMS2000 disregards further hard acceleration occurrences and leaves the compressor clutch engaged. The air conditioning will be automatically suspended if:
- The engine speed is above 6016 rpm.
- The evaporator temperature falls below 2 °C - to prevent freezing.
- The coolant temperature goes above 118 °C - to protect the engine.
- The AC system pressure goes above 30 Bar to protect the system.
- The AC system pressure goes below 1.6 Bar - to protect the system.
- The accelerator pedal is fully depressed (continuous full pedal demand) for more than 5 seconds.
- The accelerator pedal is depressed rapidly (instantaneous full pedal demand) for more than 2 seconds.
- The engine speed is below 500 rpm (engine stall).
The system will revert back to normal operation once the reason for suspension has been removed.