In this episode of The Trainer, master diagnostician and Motor Age Technical Editor, Brandon Steckler discusses how to determine the functionality of a component via current flow. Utilizing a multi-trace lab scope and current probe Brandon captures aspects of circuit operation in both a functional A/C compressor clutch circuit as well as a faulted one. It all begins with studying the wiring diagram for the vehicle in question and building a game plan before approaching the vehicle. Executing the game plan at the vehicle yields answers to the questions.
The difference between a functional A/C compressor clutch and one that does not function is easily discerned by viewing the current ramp waveform. Brandon points out key signatures in the capture that tell the story of an issued command and an adequate response to the command being issued. These include:
- Available voltage to the A/C compressor clutch relay
- The output voltage from the relay once activated (command issued)
- Current flow through the A/C compressor clutch field coil circuit (electrical work being performed)
- Physical shuttling of the A/C compressor clutch (physical work being performed)
Allow your approach to help you gain insight into system functionality, regardless of the systems or components you are faced with. This technique being discussed applies to every vehicle you will encounter so, tune in and take your vehicle diagnostics to the next level.
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