LSE9x Can Box Ac Setup
The LSE9x can box sends the current state of the max ac button and the standard ac button the Holley Terminator via Can, no inputs are used. Now that the Holley knows the state of the ac button, we can configure a Holley output that will be used for our Ac clutch control. An output can be configured that looks at the state of the ac switch, rpm, coolant temperature, throttle position, ac pressure or any desired combination. Once the configured state is met, the Holley will fire one if its ground outputs. This output will be wired to a relay which will send fused 12v power to the AC clutch, thus turning on the ac.
Ac button input: The ac button input will be configured as a can type input with the configuration as show in the screenshots below. Please note the can id and type are important, otherwise the input will not work. Once configured correctly you will have an input that will show 0 when the max ac button or the ac button is off, and 256 when the max ac button of the ac button is on. Please note that currently, turning the fan speed all the way down will not disable the compressor input, even though the lights on the ac buttons turn off. To turn the ac compressor off, press the ac button to the off position.
Ac pressure: Ac pressure input can be wired to the factory bmw ac pressure transducer. The ground and 5 volt signals should still be provided by the body harness so you only need to tap into the pressure signal wire (typically a white with black stripe). You can wire this to any of the Holley input wires and configure it as shown. Please note that the exact ac pressure scaling is still being determined so check the scale as you charge the ac system.
Ac compressor output: The ac compressor output will be configured as a ground type. The configuration of the output logic is up to the end user but our standard configuration is shown. The time delay is used to allow idle up and fan speed to increase before turning on the compressor.
Ac idle Up:
When the ac compressor is engaged, additional load is put on the engine which requires changes in idle control. This can be done multiple ways but the typical configuration with drive by wire is shown below.
Command additional idle speed when the ac button is engaged:
Add additional base idle percentage when the ac button is engaged:
Fan speed control with ac: When the ac system is active, the cooling fan needs to be on to cool the condenser, otherwise the high side pressure with be uncontrollable. The configuration of the BMW fan is shown in another article but can be slightly modified as shown below. This configuration will allow the fan to turn on at commanded speed as soon as the ac button is pressed.
System Wiring Diagram: Thanks Fred for the diagram!