Handling the pressure - There are a number of tips and techniques to help make your air-conditioning season more profitable. - Motor Age - Automotive training, certification & parts info
Before connecting your equipment to a vehicle, look for signs of sealant by visually inspecting service ports, and use a refrigerant
identifier.
For many, the first days of spring mark the beginning of a new A/C service season. For those of us living in the South, A/C
service is a year-round business. If we can diagnose A/C problems more efficiently, service them properly and reduce the chance
of comebacks, we can add more dollars to the bottom line. Let's take a fresh look at routine A/C service and see if I can
offer a few tips to help you accomplish these goals.
Before You Connect
Bob's A/C isn't cooling like he thinks it should. His buddy, Ima Fixeruper, tells him, "It just needs a little freon." Ima
just happens to have ordered some online, and Bob's more than welcome to it. Oh yeah, he's also got this self-sealing stuff
Bob can put in, just in case. Can't hurt, right?
Servicing Hybrid A/C Systems
A few months later, the car isn't cooling at all. Bob is now in your shop, but he isn't telling you he installed sealant and
a blend refrigerant in his car. This certainly should make the case that you should use a refrigerant identifier on every
car before you connect your shop's service equipment. They are available from simple units to high tech jobs; the choice is
yours. Before you connect your service equipment, look for signs of sealant by visually inspecting both service ports. Take
a sample and identify what's in the system. It will protect your equipment, your refrigerant supply and, most importantly,
it will protect you.
Now That It's Safe
Once you've verified the system isn't contaminated, connect your service gauges and test the system's operation. I start with
four basic measurements: low side pressure, high side pressure, ambient air temperature and center duct temperature. Operating
pressures are affected by relative humidity and ambient air temperature at the condenser. Take this measurement a few inches
in front of the condenser itself. If you've just moved the car from a hot parking lot into an air-conditioned shop (or the
other way around), allow the system five to 10 minutes to adapt to the temperature change before taking your pressure readings.
1 Make sure you identify what's in the system before you connect your equipment.
Specifications for individual vehicles vary, and so do the testing methods used to obtain those readings. Use your service
information system to see if these pressure specs should be taken with all the doors closed or open. Most are done with the
system set to Max A/C and the blower set to high. This will impact the temperature differential between ambient air temperature
and the temperature measured at the duct, and will help you spot a weak system.
Where Is The Leak?
Most loss-of-cooling complaints are caused by loss of refrigerant in the system. This may be a normal loss over an extended
time or due to a worn seal or leaking component. The two most common methods for leak detection in use today are refrigerant
leak detectors (sniffers) and ultraviolet (UV)dyes.
2 For accurate leak testing, keep the probe tip within ¼ inch of the test point.
I spoke with Becky Firman-Wagner of INFICON, the makers of the TEK-Mate leak detector ( http://www.inficonservicetools.com/). Here are her tips for finding those pesky leaks.
Do not leak check with the engine running.
Do not clean the components with any type of solvent prior to testing. These vapors can cause false alarms with some types
of leak detectors.
Move the test probe no more than 1 inch to 2 inches per second, and hold it no more than 1 BC4 inch from the surface.
Understand your leak detector's background compensation feature.
Refrigerant is heavier than air and drips or sinks out of leak points.
Verify the leak source by removing the probe and rescanning the area.
Fans, wind and other air currents may blow away the refrigerant while testing. If possible, test in a still environment.
Know how your detector behaves when the battery is low or when the sensor or filter needs replacing.
Pete Meier is an ASE certified Master Technician and sponsoring member of iATN. He has over 35 years practical experience as a technician and educator, covering a wide variety of makes and models. Now, as technical editor for Motor Age, his primary goal is to bring working technicians the information they need to succeed.
Articles by Peter F. Meier
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