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 v2773 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 20. If this error counter gets above 5 seconds, the unit will shut down.

Note that if the unit is running a while and the B2 timer expires, then if the compressor oil pressure goes low it will almost always hit the normal "Comp Oil Press (Low)" alarm since a low analog input alarm is faster the 5 seconds it takes the special alarm above to trip.