Checking Air Conditioning (A/C) System Function And Noise
Checking the air conditioning (A/C) system function and for noise
951 1207 Leakage locator 951 1207 Leakage locator
General
When fault-tracing, the ambient temperature must be at least 18°C or higher.
There is always noise when the air conditioning (A/C) system is running. The reason for this is that the refrigerant changes phase between gas and liquid at different pressures.
The air conditioning (A/C) system pump (compressor) produces a soft buzzing noise.
The A/C compressor will start when the engine is started, even if the air conditioning A/C button is in the OFF position. After a few seconds the air conditioning (A/C) compressor will stop.
The above noises are normal operational noises from the air conditioning (A/C) system.
This fault-tracing describes partially how to locate and correct abnormal noise from the air conditioning (A/C) system, such as low frequency rumble or metallic knocking, and partly how to fault trace and correct function problems.
Warning! Follow the safety instructions for working with refrigerant according to Climate control Refrigerant, safety regulations Refrigerant, Safety Regulations.
Caution! Read Climate Control first General repair instructions - air conditioning (A/C) system General Repair Instructions - Air Conditioning (A/C) System.
Continue - Checking the drive belt
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Checking the drive belt
- Ignition off.
Check the drive belt, if it is faulty - replace it.
Was the drive belt faulty?
Yes - Verification
No - Checking the compressor with continuous drive
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Checking the compressor with continuous drive
- Engine running.
- Air conditioning (A/C) switch on.
- Blower fan switch on highest speed.
Check that the air conditioning (A/C) compressor runs continuously.
Is the compressor running continuously?
Yes - Checking pipes and components
No - Checking the pressure switch (Pressostat)
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Checking pipes and components
- Ignition off.
Check that the pipe and components are unobstructed in the engine compartment.
All pipes or components are unobstructed.
Yes - Checking for metal shavings
No - Verification
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Checking for metal shavings
Note! Drain the system before checking. Emptying/vacuum pumping/filling with refrigerant Emptying/Vacuum Pumping/Filling With Refrigerant
Check if there are metal shavings in the expansion pipe. Replace the expansion pipe if necessary.
- To access / replace, see Climate control Replacing refrigerant pipe/hose or expansion valve Removal and Replacement.
Were there metal shavings in the expansion pipe?
Yes - Replacing component
No - Filling compressor oil
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Replacing component
Replace the compressor.
Continue - Vacuum check
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Filling compressor oil
Top up with 70 cm3 compressor oil according to Climate Control Oil air conditioning (A/C) system, filling Oil Air Conditioning (A/C) System, Filling.
Continue - Vacuum check
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Vacuum check
- Vacuum-pump the system for approx. 50 minutes.
Emptying/vacuum pumping/filling with refrigerant Emptying/Vacuum Pumping/Filling With Refrigerant
- Carry out vacuum check.
Was there a noticeable increase in pressure during the vacuum test?
Yes - Repairs
No - Filling
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Repairs
The system leaks - correct leakage.
Continue - Vacuum check
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Vacuum check
- Vacuum-pump the system for approx. 50 minutes.
Emptying/vacuum pumping/filling with refrigerant Emptying/Vacuum Pumping/Filling With Refrigerant
- Carry out vacuum check.
Is the vacuum check OK?
Yes - Filling
No - Remedy leakage
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Filling
- Top up refrigerant.
Emptying/vacuum pumping/filling with refrigerant Emptying/Vacuum Pumping/Filling With Refrigerant
- Carry out leak tracing with special tool 951 1207 Leakage locator 951 1207 Leakage locator Leak tracer.
Is the leak tracing OK?
Yes - Verification
No - Repairs
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Remedy leakage
- Remedy leakage.
- Vacuum-pump the system for approx. 50 minutes.
- Top up refrigerant.
Other information
- Emptying/vacuum pumping/filling with refrigerant Emptying/Vacuum Pumping/Filling With Refrigerant
Continue - Verification
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Checking the pressure switch (Pressostat)
- Ignition off.
- Disconnect the pressure switch (Pressostat) connector.
Connect an ohmmeter to both pressure switch (Pressostat) terminals.
The ohmmeter should read approximately 0 ohm.
OK - No Fault Found
Not OK - Checking pressure on low pressure side
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Checking pressure on low pressure side
Connect filling point low pressure side to service valve. The pressure must be 320 kPa.
Is the pressure higher or lower than 320 kPa?
Low - Leak tracing and function check
High - Replacing component
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Leak tracing and function check
- Engine running.
- Air conditioning (A/C) switch on.
- Blower fan switch on highest speed.
Carry out leak tracing with special tool 951 1207 Leakage locator 951 1207 Leakage locator Leak tracer.
Is there a leak?
Yes - Draining
No - Verification
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Repairs
- Drain the refrigerant from the system.
Emptying/vacuum pumping/filling with refrigerant Emptying/Vacuum Pumping/Filling With Refrigerant
Remedy leakage.
Continue - Vacuum check
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Draining
- Drain the refrigerant from the system.
Emptying/vacuum pumping/filling with refrigerant Emptying/Vacuum Pumping/Filling With Refrigerant
Continue - Vacuum check
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Verification
Hint: After the repair it is necessary to check that the fault has been found and corrected.
Carry out the following:
- Ignition off.
- Reinstall connectors, components etc.
- Connect the filling point's low pressure side (blue hose) to the service valve.
- Start the engine and allow it to run at 1500-1600 rpm.
- Place blower fan switch in the lowest active manual position.
- Place air conditioning (A/C) switch to on.
- Place REC-switch to on.
Check that the compressor switches in and out within the specified values:
The compressor should switch on at 295-325 kPa.
The compressor should switch off at 150-170 kPa.
Does the compressor switch in and out within the specified values?
Yes - Verification, continued
No - Checking pressure switch (Pressostat)
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Verification, continued
- Run the engine at 1500-1600 rpm.
- Turn the passenger compartment temperature selector to maximum cooling.
- Place air conditioning (A/C) switch to on.
- Air distribution selector to VENT.
- REC switch to on position.
- Set the blower fan switch to approximately 70% of full speed.
- Close the hood.
- Close doors and windows.
- Apply a thermometer in one of the central dashboard vents.
- Allow the system to stabilize itself for at least 8 minutes.
Continue - Verification, continued
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Verification, continued
- Run the engine at 1500-1600 rpm.
Check temperature in the central dashboard vents.
The read off temperature should be within the specified values.
A is outside temperature, measured in front of the car, and B is the temperature of expelled air in the central dashboard vents:
- If A is 20 °C, B must be 5-8 °C.
- If A is 30 °C, B must be 5-8 °C.
- If A is 40 °C, B must be 8-12 °C.
Is the temperature within the permitted values?
Yes - FAULT FOUND
No - Fault-tracing information, continued
No Fault Found
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Fault-tracing information, continued
Information
Fault-tracing information
The fault should be diagnosed and remedied. Since this is not the case the fault-tracing process has failed.
Complete the fault-tracing for those fault or try again.
Do you want to terminate fault-tracing at this time?
Yes - Exit fault-tracing
No - Attempt New Test
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Attempt New Test - Checking the drive belt
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Checking pressure switch (Pressostat)
- Filling point low pressure side (blue hose) connected to service valve.
- Engine idling.
- Place blower fan switch to position 0.
- Place air conditioning (A/C) switch to off.
- Disconnect the pressure switch (Pressostat) connector.
Start the compressor by connecting the magnetic clutch cable to the battery positive terminal.
Warning! The compressor may be connected like this for a maximum of 3 minutes.
Connect an ohmmeter over both pressure switch (Pressostat) terminals.
Note! If the pressure falls below 140 kPa, but the ohmmeter continues to display 0 ohms, stop and disconnect the compressor.
The ohmmeter should read infinite resistance at a compressor pressure of 150-170 kPa.
OK - Fault-tracing information
Not OK - Replacing component
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Replacing component
- Replace faulty pressure switch (Pressostat).
Note! There is a valve in the terminal, because of which it is not necessary to drain the system of refrigerant.
Continue - Verification
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Fault-tracing information
The pressure switch (Pressostat) is OK. This indicates that the fault may lie in the components and circuits which store the diagnostic trouble codes (DTCs) in the engine control module (ECM). Fault-tracing these components and circuits is not carried out here, read off the diagnostic trouble codes (DTCs) and fault-trace in the engine management system.
Continue - Fault-tracing information, continued
No Fault Found
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