Before you touch a wire, read the lights. FRC hardware is covered in status LEDs that tell you exactly what stage of the system has failed, and WPILib publishes an exact reference for every one.
roboRIO Power LED is your first stop:
- Solid green = power is good.
- Amber = brownout protection tripped, outputs disabled. This is the single most common 'my robot stopped moving' cause. Go to the brownout lesson.
- Red = power fault; check the user rails (6V/5V/3.3V) for a short circuit. Unplug things on the user rails one at a time.
roboRIO Status LED (separate from Power):
- Off after boot = normal.
- 2 blinks = software error, reimage the roboRIO.
- 3 blinks = safe mode; restart and reimage if it persists.
- 4 blinks = code crashed twice without rebooting; reboot.
roboRIO Comm LED:
- Off = no communication with the Driver Station (radio/Ethernet problem).
- Red solid = talking to the Driver Station but no user code running (deploy code).
- Red blinking = E-stop triggered.
- Green solid = good comms with the DS.
Robot Signal Light (RSL): solid ON when the robot is powered but disabled, blinking when enabled, OFF if the robot is unpowered or the RSL is miswired. An RSL that is solid when you expect blinking means your code is not enabling, not an electrical fault.
Power Distribution:
- CTRE PDP: a green strobe/blink indicates enabled with no fault, slow green indicates disabled with no fault, orange indicates a sticky fault, and red indicates no CAN comms.
- REV PDH: solid green = comms with the roboRIO established; solid blue = powered but no comms; orange/red = fail-safe.
Motor controllers (Talon FX/Kraken): solid orange = powered, on the bus, neutral output (blinking/alternating orange instead means valid CAN traffic but the device is disabled or robot code isn't running); green = driving forward; red = reverse; any red blip while jostling wires = loose CAN.
The decision tree:
- roboRIO Power amber -> brownout. Power red -> user-rail short.
- Power green but Comm off/red -> communications or no-code problem, not power.
- PD red/blue -> CAN comms lost to the PD.
- One motor dead while others work, controller LED blinking (any color, not solid) or no LED (REV) -> that device lost CAN signal or power; jostle-test its harness.
Reading lights first turns a 30-minute teardown into a 30-second diagnosis.
the part worth keeping
Key takeaways
- roboRIO Power LED amber = brownout; red = user-rail short; green = power healthy.
- Comm LED red-solid means no user code is running, not a wiring fault; red-blinking means E-stop.
- A red LED blip on a CAN device while jostling the harness pinpoints a loose connection at that segment.
Electrical & WiringCommon Mistakes & Troubleshootinglesson 1 of 5
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Sources and corrections
This lesson is AI-assisted: drafted from primary sources, then reviewed and edited by hand. Errors still get through. When one is reported we fix it and write down what changed, in public, in the corrections log.
sources and further reading
- docs.wpilib.orgWPILib: Status Light Quick Reference
- docs.revrobotics.comREV: PDH Troubleshooting
clipped to this lesson
Articles that go further on this
The lesson gets you through the topic. These go wider on it, and they read in one sitting.
- 13 min readFRC Status Lights & Blink Codes: The Complete DecoderDecode every FRC status light: roboRIO, PDH/PDP, SPARK MAX, Kraken/Talon FX, CANcoder, VH-109 radio, plus Driver Station error codes. Verified against./blogread it
- 7 min readFRC LED Lights: Wiring, Power Budgeting, and the WPILib AddressableLED APIHow to wire addressable LEDs off the PDH's switchable channel, budget their current draw, and use WPILib's AddressableLED API to signal robot state./blogread it
- 7 min readFRC "No Robot Code" & Driver Station Won't Connect: Full Fix ChecklistA verified, step-by-step FRC troubleshooting decision tree for "No Robot Code" and a Driver Station that won't connect to the roboRIO — most common causes first./blogread it
answer sheet
Lesson quiz
All 3 right completes the lesson. Miss one and only that question comes back, anything you already answered correctly stays banked.
0 of 3 answered
01While diagnosing a robot, you notice the roboRIO Power LED is solid amber (orange) instead of green. What does this indicate?
02The roboRIO Comm LED is solid red. Following the diagnostic decision tree, what is the most likely cause?
03The Robot Signal Light (RSL) is glowing solid rather than blinking. What state is the robot in?
Answer every question to submit.
All 35 lessons in Electrical & Wiringopenclose
01 / prerequisites
02 / control-system-components
03 / power-battery-breakers
04 / motor-controllers-can-bus
05 / connections-rules-troubleshooting
06 / worked-examples-mini-projects
- Not read yet:Mini-Project 1: A Single-Motor Test Stand from Battery to Spin
- Not read yet:Mini-Project 2: Current-Limited Drivetrain (CTRE and REV)
- Not read yet:Mini-Project 3: A Live Power-Monitoring Dashboard
- Not read yet:Mini-Project 4: A Switchable Channel for Lights and Vision
- Not read yet:Mini-Project 5: CAN Device Bring-Up with Tuner X and the Hardware Client
07 / common-mistakes-troubleshooting
08 / advanced-techniques-case-studies