For the vast majority of cars our first check is to ascertain the pressure of refrigerant in the system. If this appears too little for what we know about the car then we start investigating with electronic leak detector and UV lamp to check that there are no leaks in the system. If pressures are reasonable when static we then start to check pressures under operating conditions to see if the compressor is doing its job and any condenser fans are working correctly. For exceptionally small refrigerant leaks we also have a detection system that uses the smallest molecule in the universe in order to find what is able to wriggle through the tiniest gap.
The complexity of modern car air conditioning or climate control can sometimes result
in a failing AC system that will not respond to just a routine vacuum and recharge
service. In these circumstances the requirement is for good observational skills
to detect operational abnormalities, extensive vehicle data files to act as
a reference point, a wealth of AC experience and an analytical brain to utilise
these factors and come up with the solution.
Our first response to an electrical fault is a Power Probe and a Digital Multimeter.
Increasingly however electronics rather than just electrics are responsible for many
problems and additional tools have to be be employed. Electronic Diagnostic Tools, able
to communicate with the onboard computers controlling much of the cars operation are
necessary for virtually all post 2000 vehicles.
These can identify malfunctioning parts
and can remove Fault Codes generated after the faulty part has been replaced. These
Diagnostic Tools interrogate the small network of computers that control most operations
in modern vehicles and which generate a DTC, a Fault Code, to signal that some component
is not doing what it is supposed to. An example of this might be that a small electric
motor, designed to turn a flap which controls the mixture of hot and cold air entering
the cabin which regulates the drivers temperature might have seized up. A Fault Code is
now generated to signal to the technician which component is faulty and needs replacing.
Fault Codes are not always generated however and in these cases we have to dig deeper to
find the problem.
We also use a Multi-channel Oscilloscope to observe the actual waveform generated
by whatever control module in the car we are investigating. To complement that
we have variable width squarewave generators to simulate the action of the AC
Control Module as it controls the latest generation of AC compressors or stepper
motors. In the hands of an experienced technician these pieces of specialised
test equipment are invaluble and can help diagnose most problems but if the
brain behind the tool is inexperienced the outcome may be disappointing.
In the process of investigating AC faults our High Tech equipment can sometimes reveal other related Fault Codes and sometimes Fault Codes completely unrelated to the AC system can be detected which we are often able to correct. For example a problem with a rear door window motor in the past may have generated a Fault Code which may prevent the central locking system working correctly. This may be identified in the process of investigating an AC fault and can be corrected simultaneously.
To be frank, some of our most testing electrical problems have been very low tech - they have simply been the result of a bad connection, sometimes badly corroded or a wire actually broken. Mostly we can find these but sometimes we are forced to refer these to another specialist, an auto electrician.