Faster, easier ways to diagnose a/c systems

 airconditioner

airconditioner

Trying to diagnose the precise cause of an automobile air conditioning system can be frustrating and very time consuming for most technicians. Because there are many components that make up the a/c system on modern vehicles; there are virtually dozens of potential mechanical or electrical faults which can contribute to an a/c unit that isn’t working inside the vehicle.

But just like any other mechanical problem(s), there are a few tips and processes that anybody troubleshooting can follow, which will speed up the diagnosis process and complete air conditioning system repairs faster and easily.

Below are a few suggestions that can help a technician of any level or experience find the root cause of most a/c issues that plague vehicle owners.

Start with a diagnostic scan: If a vehicle was made after 1996 (i.e., OBD-II compliant vehicles), it’s very likely that the majority of issues have been recorded on and are available for download from the vehicle’s Engine Control Module (erroneously but commonly called “brainbox” in local roadside mechanics’ parlance).

Virtually every system of a vehicle is monitored with sensors and connectors that stream real-time data to the vehicle’s ECM; this includes the air conditioning system on most modern automobiles. As such, the best way to begin any diagnosis is to download any error codes stored inside the vehicle’s ECM with a digital scanner.

Most technicians invest money in ensuring they have the best tools to complete repairs efficiently. However, when they use a high-quality scanner that can download all error codes, the process of finding the root cause of anything that is not functioning correctly in a vehicle becomes much quicker.

Complement digital scanning with a physical inspection of the air conditioning system: After the technician has completed the digital scan and found any error codes, those findings will typically lead them to a specific section or piece in the air conditioning system. However, before diving into the engine compartment and removing parts and pieces; it’s a good idea to complete a physical inspection of the system. Just like a test drive, this will give the mechanic a real-time view of the problems that customers are experiencing.

compressor

Here are a few steps to consider when completing a physical inspection of the a/c system in any vehicle: Turn on the a/c while the vehicle is running. Turn the a/c switch to the fresh air setting (this will ensure the air is not recirculated which can produce misleading results). Make sure the a/c switch is at its highest setting.

Once the technician has set the a/c system up to monitor, they should listen, feel and smell for any symptoms that will indicate problems with certain a/c components.

Listen: By listening to the a/c system as it is fully engaged, the mechanic can determine where problems are occurring. Noises like a grinding noise or clunking sound might indicate a problem exists with the air conditioning system’s motor or compressor. It might also indicate a problem exists with the cabin filter if it sounds like the a/c system is struggling to push air into the cabin.

Feel: By taking time to feel the air blowing into the cabin, the mechanic can also pinpoint other mechanical issues. If the air is warm, it typically indicates that problems with the a/c system includes low coolant, or issues with the compressor. It’s also important to feel the air for the pressure it’s supplying into the cabin. If the pressure is low, it’s most likely due to blockage in the ventilation system; such as the filters or the vents themselves. This can, and often does cause many of today’s issues with a/c systems.

Smell: By smelling the air that circulates through the vehicle, the mechanic can also determine if a coolant leak exists or, again, that the cabin air filter needs to be replaced.

Complete under-the-bonnet examination: After downloading error codes and completing a physical inspection of the vehicle’s a/c system, it will be important for any technician to complete an under-the-bonnet inspection. During this inspection, a good technician will complete the following:

Look for any coolant leaks. A closed a/c system does not leak coolant; so if the air is warm, it’s most likely caused by a coolant leak. Fix the leak then recharge the system.

Check for freezing. If during your physical inspection you notice that the air was cool, but then got warm, it may be due to excess moisture inside the a/c lines that will contribute to freezing the compressor.

Check for vacuum leaks: Many a/c systems rely on vacuum pressure to run efficiently.

Most of today’s problems with a/c systems can be easily diagnosed when a mechanic completes the above process for diagnosing a problem with the system.

NB: Parts of this piece were culled from the Internet.

Diagnostic codes

P0226 – Throttle/Petal Position Sensor/Switch ‘C’ Circuit Range/Performance Problem: Electric Throttle Control Actuator consists of throttle control motor, throttle position sensor (TPS), etc. The throttle position sensor responds to the throttle valve movement.

The throttle position sensor has the two sensors. These sensors are a kind of potentiometers which transform the throttle valve position into output voltage, and emit the voltage signal to the ECM. In addition, these sensors detect the opening and closing speed of the throttle valve and feed the voltage signals to the ECM. The ECM judges the current opening angle of the throttle valve from these signals and the ECM controls the throttle control motor to make the throttle valve opening angle properly in response to driving condition.

The code is detected when an out-of-range voltage from the TPS is sent to ECM.

Possible causes: Faulty TPS, TPS harness is open or shorted, TPS circuit poor electrical connection.

P0227 – Throttle/Petal Position Sensor/Switch ‘C’ Circuit Low Input: Electric Throttle Control Actuator consists of throttle control motor, TPS, etc. The throttle position sensor responds to the throttle valve movement.

The throttle position sensor has the two sensors. These sensors are a kind of potentiometers which transform the throttle valve position into output voltage, and emit the voltage signal to the ECM. In addition, these sensors detect the opening and closing speed of the throttle valve and feed the voltage signals to the ECM. The ECM judges the current opening angle of the throttle valve from these signals and the ECM controls the throttle control motor to make the throttle valve opening angle properly in response to driving condition.

The code is detected when an excessively low voltage from the TPS is sent to ECM.

Possible causes: Faulty TPS, TPS harness is open or shorted, TPS circuit poor electrical connection.

P0228 – Throttle/Petal Position Sensor/Switch ‘C’ Circuit High Input: Electric Throttle Control Actuator consists of throttle control motor, TPS, etc. The throttle position sensor responds to the throttle valve movement.

The throttle position sensor has the two sensors. These sensors are a kind of potentiometers which transform the throttle valve position into output voltage, and emit the voltage signal to the ECM. In addition, these sensors detect the opening and closing speed of the throttle valve and feed the voltage signals to the ECM. The ECM judges the current opening angle of the throttle valve from these signals and the ECM controls the throttle control motor to make the throttle valve opening angle properly in response to driving condition.

The code is detected when an excessively high voltage from the TPS is sent to ECM.

Possible causes: Faulty TPS, TPS harness is open or shorted, TPS circuit poor electrical connection.

P0229 – Throttle/Petal Position Sensor/Switch ‘C’ Circuit Intermittent: Electric Throttle Control Actuator consists of throttle control motor, TPS, etc. The throttle position sensor responds to the throttle valve movement.

The throttle position sensor has the two sensors. These sensors are a kind of potentiometers which transform the throttle valve position into output voltage, and emit the voltage signal to the ECM. In addition, these sensors detect the opening and closing speed of the throttle valve and feed the voltage signals to the ECM. The ECM judges the current opening angle of the throttle valve from these signals and the ECM controls the throttle control motor to make the throttle valve opening angle properly in response to driving condition.

The code is detected when an intermittent voltage from the TPS is sent to ECM.

Possible causes: Faulty TPS, TPS harness is open or shorted, TPS circuit poor electrical connection.

P0230 – Fuel Pump Primary Circuit Malfunction: The ECM provides ignition positive voltage to the coil side of the fuel pump relay. When the ignition switch is first turned on, the ECM energises the fuel pump relay, which applies power to the fuel pump. The ECM enables the fuel pump relay as long as the engine is cranking or running, and crankshaft reference pulses are received. If no crankshaft reference pulses are received, the ECM de-energises the fuel pump relay after two seconds. The ECM monitors the voltage on the fuel pump relay control circuit.

The code is detected when an incorrect voltage on the control circuit of the fuel pump relay is detected by the ECM.

Possible causes: Blown fuel pump fuse, open fuel pump monitor circuit, faulty fuel pump relay, damaged ECM.

About the Author

Leave a Reply

*