Weber, president of Virginia-based Write Stuff Communications Inc., is an award-winning freelance automotive and technical writer with over three decades of journalism experience. He is an ASE-certified Master Automobile Technician, and has worked on automobiles, trucks and small engines. He is a member of the Society of Automotive Engineers (SAE) and numerous other automotive trade associations. He has worked as an auto mechanic, a shop manager and a regional manager for an automotive service franchise operation.
The advent of computer controls, and especially with the 2000 introduction of CAN (controller area network), has changed much of the way we service automobiles. The heating/ventilation/air conditioning (HVAC) system is no exception.
When is the last time you pulled out your manifold gauges and hooked them up to the refrigerant lines’ fittings? It is so much quicker, easier and accurate to plug your scan tool into the diagnostic link connector (DLC) and get the pressure readings digitally. Of course, some systems also use the self-diagnostics of the HVAC control head in the dash by pushing various buttons or a similar method.
The cool thing about scan tool diagnosis is bidirectional control allowing the technician to check the operation of such things as the compressor clutch relay, blend door position and such. The scan tool can also report powertrain related diagnostic trouble codes (DTCs), those with the P prefix as well as body control module codes that have the B prefix. In some cases, network codes having the U prefix are also available.
What has not changed is how we service the air conditioning system components at the mechanical level. Compressors, condensers, evaporators and blowers still require wrenches in the skilled hands of agile technicians. Granted, accessing some of the components has become a hassle over the years though.
What has changed is system control and management. Electronics and their myriad sensor inputs are the realm of the skilled minds who must diagnose them. Here, we shall review many of those components, their function and their testing.