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Air con diagnostics and repairs

By autotech-nath on May 27, 2019

Snap-on can provide workshops with handheld tools and garage equipment to diagnose and repair vehicles that come into the workshop with the air conditioning warning light illuminated. 

By connecting the Snap-on ZEUS scan tool, you can discover the fault codes that are causing the AC warning light to be illuminated. Once established, the Sun KoolKare Blizzard PRO can be connected
so that the gases in the vehicle’s AC system can be removed safely before repair work begins. 

Having completed the repair, the Blizzard PRO can then pressure test the system with the nitrogen pressure function, followed by a vacuum of the system to remove all the non-condensables before filling with the required gas. You can then run the vehicle to check the air conditioning system is operating at correct pressures. The last stage is to re-connect the ZEUS to check the AC system is now working correctly and that there are no further fault codes, and also to clear any codes present. 

Actuator testing 

Many cars now have air conditioning, or climate control – systems that contain high and low pressure sides, compressors, condensers, evaporators and refrigerant, plus many more components. 

Most comfort systems now have some form of diagnostic capabilities, from codes only, codes and data, or actuators. Snap- on says its ZEUS scan tool can aid you in an actuator test. 

Figure 1

Focusing on automatic air conditioning from a 2005 Mercedes- Benz E-Class (W211), in Figure 1 the actuators have been selected, so that you can find lists of them, Figure 2. When automatic air conditioning is working correctly, all of the components listed as actuators will be commanded by the control module to perform a given task. When a system is not working properly, diagnosing the automatic air conditioning can be a difficult task. By using a diagnostic tool, you can actuate many of the components fitted in the system – like the blend motors, blower, hot and cold taps. These components are usually in hard-to-reach places at the rear of the dashboard, making access incredibly difficult. 

Figure 2

While running such actuators on the ZEUS it may not be possible to see or hear the actuation events, but the tool can view the oscilloscope while using the scanner. This will assist in diagnosing the system, running the actuator and viewing the scope monitoring the signal wire to a given component. The signal wire could be a simple PWM (Pulse Width Modulation) or LIN (Local Interconnecting Network). 

However, before you rush in with diagnostic tools, it is important to make sure the basics have been checked first – ensuring that the mechanical system is good, visually inspecting the system, checking the correct amount of refrigerant and PAG oil, referring to technical data and using an air conditioning service station. 



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