Multiplex / networked controls
A guided diagnosis for RV techs. Each step is a check, a reading or a question.
- OneControl, Firefly, Spyder: what is wrong? A network of modules replaces the switches. Each module needs 12V, ground and the data bus. A touch panel or phone app talks to the modules through a gateway. Expect: 12V and ground at every module, the bus terminated
- 12V and ground at the main controller or gateway? Find the main module (often in a basement bay or behind the panel) and meter its power plug. Expect: 12 to 13.6 V
- 12V at the module output when you command the function? Find which module drives it (the system's device list or the wiring label). Meter the output terminal to ground while someone presses it. Expect: 12V on the output while commanded
- Power off. Ohms between CAN-H and CAN-L at any module plug? Unplug the system power or pull the main fuse. Meter across the two data pins. Expect: About 60 Ω
Causes and repairs
Controller feed
The system's fuse or breaker at the 12V panel, the battery disconnect, or a loose ground stud.
Tools: multimeter, clamp meter
Fuse first, then the ground. Clamp the feed when it comes back on: a large draw with nothing commanded is a short downstream.
The load or its wire
The module is doing its job. Meter at the load: 12V there means the load or its ground; nothing there means an open wire between.
Tools: multimeter
Repair the wire or replace the load. Check grounds at the load end.
Module output or its fuse
Many modules have a fuse per output. Check it first. Good fuse and no output: the output driver failed (often after a short on the load).
Tools: multimeter
Replace the fuse and find out why it blew. Replace the module if the output is dead; re-pair or re-assign it in the system after.
Bus wiring is good: power or a module
Termination is right, so the wire run is complete. Power up and meter each data line to ground: about 2.5 V idle on both. A module holding the bus down shows up as one line stuck high or low; unplug modules one at a time to find it.
Tools: multimeter
Unplug modules one by one until the bus comes back. Replace that module.
Terminator missing
One end of the bus lost its terminating resistor, usually an unplugged end module or a terminator plug that fell off.
Tools: multimeter
Find the end of the bus and reinstall the terminator or reconnect the end module.
Bus open
A connector off or a data wire cut, often at a slide or a bay door.
Tools: multimeter
Ohm segment by segment to find the break. Repair with a proper splice; keep the pair twisted.
Bus shorted
CAN-H and CAN-L touching: water in a connector, a pinched cable, or a failed module.
Tools: multimeter
Unplug segments until the short clears. Dry or replace the connector, repair the cable.
Gateway or pairing
The Bluetooth or WiFi gateway needs 12V and the bus. A phone that paired once and stopped usually needs the old pairing deleted.
Tools: multimeter
12V at the gateway, power cycle it, delete the device in the phone's Bluetooth list, re-pair per the brand's procedure.
Stuck input or water
A wall switch input stuck closed, water in a switch or connector, or a wire chafed to another.
Tools: multimeter
Watch the panel's input status (if it has one) while you press and wiggle switches. Replace a stuck switch, dry a wet connector, repair the chafe.