Checking Air Conditioning (A/C) System Function And Noise
Checking air conditioning (A/C) system function and noise
951 1207 Leakage locator 951 1207 Leakage locator
General
When fault-tracing ambient temperature should always be at least 18°C or above.
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 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, low frequency rumble or metallic knocking, 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 drive belt
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Checking drive belt
- Ignition off.
Check drive belt, if it is faulty - replace it.
Was the drive belt faulty?
No - Checking the compressor with continuous drive
Yes - Verification
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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 fan runs continuously.
Is the compressor running continuously?
Yes - Checking pipes and components
No - Checking pressure switch (Pressostat)
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Checking pipes and components
- Ignition off.
Check that the pipe and components are free in the engine compartment.
All pipes or components are free.
Yes - Checking for metal shavings
No - Verification
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Checking for metal shavings
Note! Drain the system before checking according to Climate control Emptying/vacuum pumping/filling with refrigerant Emptying/Vacuum Pumping/Filling With Refrigerant.
Check if there are metal shavings in the expansion pipe, if necessary replace expansion pipe.
- 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 compressor according to Climate control.
Continue - Vacuum check
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Filling compressor oil
Top up with 70 cm3 compressor oil according to the Climate control.
Continue - Vacuum check
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Vacuum check
- Vacuum pump the system for approximately 50 minutes according to Climate control Emptying/vacuum pumping/filling with refrigerant Emptying/Vacuum Pumping/Filling With Refrigerant.
- Carry out vacuum check.
Does the vacuum decrease noticeably during the vacuum check?
No - Filling
Yes - Repair
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Repair
The system leaks - correct leakage.
Continue - Vacuum check
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Vacuum check
- Vacuum pump approximately 50 minutes according to Climate control Emptying/vacuum pumping/filling with refrigerant Emptying/Vacuum Pumping/Filling With Refrigerant.
- Carry out vacuum check.
Is the vacuum check OK?
No - Remedy leakage
Yes - Filling
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Filling
- Top up refrigerant according to Climate control 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 - Repair
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Remedy leakage
- Remedy leakage.
- Vacuum pump approximately 50 minutes according to Climate control Emptying/vacuum pumping/filling with refrigerant Emptying/Vacuum Pumping/Filling With Refrigerant.
- Top up refrigerant according to Climate control Emptying/vacuum pumping/filling with refrigerant Emptying/Vacuum Pumping/Filling With Refrigerant.
Continue - Verification
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Checking pressure switch (Pressostat)
- Ignition off.
- Disconnect the pressure switch (Pressostat) connector.
Connect an ohmmeter to both pressure switch (Pressostat) terminals.
The ohmmeter should indicate approximately 0 ohm.
Not OK - Checking pressure on low pressure side
OK - No Fault Found
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Checking pressure on low pressure side
Connect filling point low pressure side to service valve. pressure should 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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Repair
- Drain the system of refrigerant according to Climate control Emptying/vacuum pumping/filling with refrigerant Emptying/Vacuum Pumping/Filling With Refrigerant.
Remedy leakage.
Continue - Vacuum check
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Draining
- Drain the system of refrigerant according to Climate control 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 filling point low pressure side (blue hose) to service valve.
- Start the engine and allow to run at 1500-1600 rpm.
- Switch blower fan switch to the lowest active manual position.
- Switch air conditioning (A/C) switch to on.
- Switch REC-switch to on.
Check that the compressor switches to 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
- The engine runs at 1500-1600 rpm.
- Switch the passenger compartment temperature selector to maximum cooling.
- Switch air conditioning (A/C) switch to on.
- Air distribution selector to VENT position.
- REC switch to on position.
- Set the blower fan switch to approximately 70% of full speed.
- Close 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.
Select "Continue".
Continue - Verification, continued
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Verification, continued
- The engine runs 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 should be 5-8 °C.
- If A is 30 °C, B should be 5-8 °C.
- If A is 40 °C, B should 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 drive belt
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Checking pressure switch (Pressostat)
- Filling point low pressure side (blue hose) connected to service valve.
- Engine idling.
- Switch blower fan switch to position 0.
- Switch 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.
Not OK - Replacing component
OK - Fault-tracing information
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Replacing component
- Replace faulty pressure switch (Pressostat).
Note! There is a valve in the terminal, therefore 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 can 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.
Select "Continue".
Continue - Fault-tracing information, continued
No Fault Found
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