Over time, diesel fuel can leak past the plungers and dilute the lubricating oil.
| | Meaning (per manual) | Solution | | :--- | :--- | :--- | | Solid Green | Normal operation, communication OK | No action needed | | Blinking Green (slow) | Power OK, no bus communication | Check RS-485 wiring (A & B polarity) | | Blinking Red | Address conflict with another module | Cycle DIP switches; power cycle the panel | | Solid Red | Internal failure or short on zone input | Disconnect field wiring; test each zone for shorts | | Off | No power | Measure voltage at terminals (10.5–14V DC required) | bosch pes4a manual