p Fig. 3: Here, the screen of the Snap-on Tools Diagnostic Thermal Imager (No. EETH300) displays the thermal temperature reading of a heated seat on a vehicle. Addressing an intermittent A/C issue Temperature testing tools, such as infrared thermometers and thermal imagers, help to diagnose and check repairs on an intermittent air conditioning system issue. Modern automotive p Figs. 8 and 9: thermal imager has many uses in HVAC, such as obtaining the temperature of components within the dash without removing dash panels to get at the component. The image on the abve left shows dash vents in normal work order, indicated by the consistent temperature reading for all three vents. The image on the above right shows an inconsistency with the temperature of the dash vents, indicating a restriction blocking the warm air from entering/exiting the vent. Tool Briefing By Barry Hoyland, Contributing Editor HVAC systems have many similarities with previous versions because they work on relatively the same principles. Even though some of the components, refrigerants and delivery methods have changed, the main purpose of HVAC is to maintain occupant comfort and safety by adjusting temperatures and keeping the windows clear by controlling humidity. Additionally, many newer vehicles have added individual comfort zone controls along with heated and cooled seats. Even though systems are similar, due to some changes in operation, such as variable displacement compressors, and with the proliferation of individual comfort controls, it is now necessary to change your approach to diagnosing issues with these systems. Tried and true methods of relying on pressure testing of the air conditioning system are no longer the starting point, nor are they conclusive tests to determine root causes of problems. Many systems now use temperature sensors, in addition to pressure sensors, as additional inputs dictating when and how the compressor and air distribution systems operate. 50 PTEN FEBRUARY 2017 www.VehicleServicePros.com p Fi 8 d 9 th l i oms mireain stinty. With that in mind, temperature testing and using the right tools to perform tests are essential to being both efficient and correct when diagnosing the system. 1 GATHER VEHICLE INFORMATION Before beginning any active testing, you should use information sources such as Alldata to check for any related TSBs and to obtain both operating theory and specifications for the vehicle you are working on. It may not be a bad idea to check the underhood label to see if the label matches the system specifications indicated in the information source. If there have been modifications, such as a retrofit or a programming change, there may be an underhood label describing the change. As with any other vehicle repair, you will need to confirm the issue utilizing information gained from the customer as to when the issue occurs. In the case of HVAC, this information is very important because the system can operate fine under some conditions and have problems with small changes to ambient (outside) air temperature or driving conditions. Our customer indicated the A/C would work fine for a time then stop blowing cool air. There were no relevant service campaigns for the air conditioning system issue. We were able to duplicate the customers’ concern during a road test. At this time, we checked the operating parameters, paying close attention to necessary pressure and temperature requirements for normal operation. You should remember, depending on where you live in the country, you may not be able to test air conditioning throughout TOOLS USED: • Vehicle information • Scan tool • RRR machine • DMM with temperature probe • Infrared thermometer • Thermal imager
Professional_Tool_And_Equipment_News_February_2017
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