Series 4 processor orange LED (RX) meaning on BUS

I have a ~10 year old Homeworks series 4 processor that runs several dimmers. Motion detector for lights on stairs stopped working a few days ago (meaning walking up or down stairs no longer triggers lights to come on). Have traced the wires back to the series 4 processor BUS 3.

BUS 3 on the side where the orange LED is on full-time does not respond to a voltage meter (all other BUS and switches do respond). Can someone tell me what might be the problem?

Everything else on the system seems to be working fine.


I have tried to upload pictures, but the attachment manager keeps telling me the files could not be uploaded/upload failed (?)

Bus 3 is the serial (RS232) connection. If you unplug the connector and the RX light stays on, the bus is bad. If the light goes out, the motion sensor is bad. You can find replacement processors online but they can get pricey.

Randyc - thank you. I unplugged it and the light went out so I assume the processor is fine and I need to replace the motion sensor?

It's kind of unusual for motion sensors to connect by serial. They typically communicate by contact closure. Do you have a HWI-CCI-8 in the system? If so, the S4 processor typically has a separate plug-in power supply for the keypads. It may be working but will not have enough power to operate the CCI/keypads when an event happens (button press, etc.). You can get a replacement transformer anywhere. Just match the electrical ratings.