This is a 2005 Honda Odyssey with an A/C system problem. The A/C clutch does not engage, even though the system is full of refrigerant. In this video I will walk you through testing system pressures, and how to test the inputs and outputs of any A/C system.

Engine Performance Diagnostics chapter 3

Topics discussed


  • A/C clutch does not engage

test shown

  • how to use system rest pressure to determine state of charge
  • how to test the A/C relay
  • how to test for an A/C switch or sensor problem by looking at RPM
  • how to test the A/C compressor clutch relay for proper control
  • how to measure A/C clutch coil current flow
  • how to check the A/C clutch for proper power and ground

Tools used

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- HVAC and Cooling systems troubleshooting

Related videos:

Eric O from SMA Ford Taurus - No A/C (clutch tap test):


How to test a blower motor and resistor (subscriber requested):


How to test a starter motor (no crank from a bad block ground) - Nissan:


Fuel pump electrical circuit diagnosis (no fuel pressure testing) GM (relay feed circuit problem):


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For more information on this topic, I have written a “field manual” called Engine Performance Diagnostics which is available as an eBook or paper book.

Want even more diagnostic training? Whether you are a DIY trying to fix your own car, someone looking to become an auto technician, or a current auto technician that wants to get more into diagnostics, subscribe to ScannerDanner Premium. There is a 14 day free trial.

On ScannerDanner Premium I will bring you right into my classroom at Rosedale Technical College. You will find page for page lectures taken right from my book as well as exclusive classroom type case studies. What is so special about these classroom case studies? I pull live problem vehicles directly into my classroom and we troubleshoot them in real time, using and applying the theory and testing procedures we learn during the classroom lectures. There is no better on-line training of how to troubleshoot automotive electrical and electronics systems anywhere!