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Error Code P0534 is defined as Air Conditioner Refrigerant Charge Loss. This means the Air Conditioning compressor clutch is cycling too frequently, a problem often caused by low refrigerant level or inoperative cooling fans.
The A/S (automotive system) is thoroughly lubricated by a combination of specially designed oil and freon. The A/C system can have an appropriate amount of oil, but there is not enough Freon, it will not be able to circulate to vital areas. This can cause serious and catastrophic failure, causing the condenser to be filled with gummy metallic debris. Thus, to protect the condenser and other important (and often expensive) components, the pressure sensors are put in certain areas of the system.
There is a high-pressure cutoff switch at the back of the compressor (or in discharge line) that works to protect the A/C system from extreme overpressure condition. This condition could be caused by lack of airflow across the condenser or overheating engine.
To protect the air conditioning system from low Freon condition, a low-pressure cutoff switch is placed in the suction side of the system, near the accumulator or the expansion valve (depending on the configuration of the A/C system).
A/C low-pressure cutoff switch is made up with pressure sensitive contact, which closes when the A/C pressure exceeds the target level (which is usually more than 30 psi). It usually shreds into the Schrader valve on the suction hose or the accumulator for the A/C system. As long as the A/C system pressure is within the specifications set by the manufacturer, the contact in the low-pressure switch will remain closed, and the A/C compressor clutch power circuit is completed as desired. But as soon as the A/C system pressure falls lower than the minimum threshold, the contact in the low-pressure switch will start to open, causing interruption to the compressor clutch.
Also, the A/C low-pressure cutoff switch works by providing the PCM (powertrain control module, also known as ECM or engine control module in other vehicle makes) with an On/Off signal. If the PCM sees a low signal coming from the low-pressure cutoff switch, that means there’s a low Freon condition, which leads to the activation of the Check Engine light and registration of the Error Code P0534 to the vehicle’s memory system.
As with other error codes, this code activates the Check Engine light and registers the code to the PCM. Other common symptoms include:
- A/C compressor switch flashing
- A/C will not blow cold air
- A/C compressor clutch engagement disabled
- Compressor clutch may cycle on and off repeatedly
- Overcharged refrigerant
- Low refrigerant
- Inoperable cooling fans
- Freon leak in the A/C system
- Open or short in A/C refrigerant pressure sensor circuit
- Bad or loose connection in AC refrigerant pressure sensor circuit
- Defective pressure sensor switch
- Defective climate control head unit
How to Check
A general performance check for the air conditioning system is recommended for this code. Note that handling certain types of Freon may require federally mandated certifications in many areas. Freon can be dangerous under high pressure. Also, the A/C system must be serviced only by qualified professionals.
Before starting your diagnosis, the A/C system must be filled with the right level and type of Freon and oil. If there are no visible specifications for this under the hood, then refer to the vehicle information. Specific tools are needed to service the A/C system, such as a set of automotive a/c gauges, a vacuum pump, and an oil dispenser. If there is a small leak, then an ultraviolet leak detection dye injection is needed to diagnose the Freon leak properly.
Once the A/C system has been serviced with the right level and type of Freon, you can now clear the codes before you can restore power to the A/C compressor clutch coil. Connect the scanner to scan the vehicle’s computer and retrieve all stored codes and their respective freeze frame data. Write this information, then clear the codes. Then, check if the code comes back.
If the core resets, use the DVOM (digital volt/ohmmeter) to check for the low-pressure cutoff switch. You can do this by starting at the engine and turning the A/C on max with the fan on high. Be very careful on working around moving parts, connect the negative test lead of the DVOM to the known good ground. Then, probe the wires of the low-pressure switch connector by testing positive test lead. This will be carried out with low-pressure cutoff switch connector plugged in. All other wires (usually three) should have a battery voltage.
If none of the circuits have voltage:
- Use the DVOM to check the system fuses
- Check the AC On/Off switch
- Check the low-pressure switch connector
- Check the A/C compressor relay
If one of the circuits have voltage, and others don’t:
- You have a defective low-pressure switch
- Check if the compressor clutch is activated by jumping the switch
- If after jumping the connector the clutch is activated, then you have a faulty low-pressure cutoff switch
- Low level of Freon is the most common cause of this code. Make sure the A/C system has the right level of Freon before diagnosing
How to Fix
The most common fix for this code is adding refrigerant, especially if the system is low on it. Other repairs include:
- Replacement of climate control head (worst-case scenario)
- Sensor replacements
- Wiring repairs
- Leak repairs
This code will not cause serious damage or safety issues. If will, however, cause your A/C system to be inoperable. As said earlier, it is extremely important to have your A/C system addressed by a qualified expert.