Special Compressor Oil Pressure Alarm

Overview

Typically a compressor oil pressure sensor will have the low alarm set to use the "B2" timer, which will be set to 15 - 30 seconds. However, if the oil pump is not working there could be damage by the time the B2 timer expires and the unit shuts down. To address this, a special alarm was added to Brain v2773 to catch when the engine starts cranking but the compressor oil pressure is not building.

Using the Alarm

To use the alarm:

1. Make sure the Brain is at v2788 or newer and the DCT is updated to 1.63.482 or newer
2. Make sure the compressor oil pressure input is using the default name "COMP. OIL PRESS."
3. Enable the alarm under Brain - Misc Settings by setting "Monitor comp. oil during crank" to "Yes"

Alarm Logic

The Brain will increment an error counter when the unit RPM is above 300 but the compressor oil pressure is below 45. If this error counter gets above 5 seconds, the unit will shut down.

Note that in normal cases where the oil pressure goes low after the unit is running a while the unit will almost always hit the normal "Comp Oil Press (Low)" alarm instead since a low analog input alarm is faster than the 5 seconds it takes the special alarm above to trip, so this alarm mainly applies during crank before the B2 timer expires.