Before blaming the board
Separate an input problem, an unmet condition, a command, and a physical response.
Input
What does the control receive? Record sensor conditions, switch states, or communications as defined by the service information. A value plausible enough to avoid a fault code can still be wrong for the actual condition.
Permission
What must be true before the control acts? Consider the selected mode and safety or sequence prerequisites in this model. A missing output may be an intended response to an unmet condition.
Output
What does the model procedure say should happen next? Distinguish a displayed request, an electrical command, and actual load movement or heat. They are different evidence.
Feedback
Does the physical result match the intended action, and does the control receive the expected response? Follow the exact harness and load checks before assigning the failure to the board.
Make the next decision.
A fictional temperature sensor is not open or shorted, but its reading has not been compared at a known temperature. Is it calibrated correctly?
Compare your reasoning
Not established. Passing an open/short screen does not prove accuracy at a known temperature. Use the model’s resistance/temperature or signal specification.
Continue in the course
AR-101: Sensors, controls, and communication ↗Original educational synthesis based on the supplied AR-101 material. First edition, October 24, 2026.
Record what supports your conclusion.
Use the evidence worksheet to separate facts and assumptions.