Attention! Before starting troubleshooting, it is necessary to check the ECU ECM "Diagnostics of the ECM of the LADA LARGUS car" using the diagnostic device for the presence of fault codes related to the operation of the air conditioning system.
This section describes the diagnostic procedure used for the air conditioning system of the LADA LARGUS.
Necessary diagnostic equipment and devices:
- diagnostic device DST-12 (rF90 firmware);
- multimeter;
- universal contact plate.
General instructions for diagnostics
To diagnose the air conditioning system, you need to connect the diagnostic device, turn on the ignition and perform the necessary operations (checking for faults, checking the compliance of data transmitted by the controller) concerning the air conditioning system, "Diagnostics of the ECU of the LADA LARGUS car".
Troubleshooting Algorithm (TSA)
If no faults are detected during the check using the diagnostic device, but the fault remains, then the appropriate fault finding procedure should be used to eliminate the fault.
The general scheme for performing diagnostics is shown in Figure 3-1 as a block diagram.
Checking the electrical wiring
Difficulties in diagnosis
By disconnecting connectors and/or moving wire harnesses, the cause of the fault can be eliminated instantly. Voltage, resistance and insulation resistance measurements usually give correct values of the measured quantities, especially if the fault is not present at the time of testing (is remembered).
Visual inspection
Find signs of damage in the engine compartment and interior. Carefully check the protective covers, the integrity of the insulation and the correct routing of the wire harnesses. Find traces of oxidation.
Touch test
When wiggling and twisting the wiring harnesses, use a diagnostic tool to determine when the fault changes from "stored" to "current." Make sure the connectors are securely fastened. Slightly "wiggle" the connectors. Twist the wire harness. If the fault status has changed, try to determine its cause.
Checking individual elements
Disconnect the connectors and check the condition of the clamps and contacts, as well as their crimping (there should be no traces of crimping on the insulation). Check that the clamps and contacts are securely fixed in the connector sockets. Make sure that the clamps and contacts are not pressed out when connecting the connector. Check the contact pressure of the clamps using a contact terminal of the appropriate type.
Resistance check
First check the integrity of the entire chain, then individual sections. Determine if there is a short circuit to ground, to +12 V, or to another wire.
If a fault is detected, fix it or replace the wiring.
General scheme of diagnostics
Troubleshooting Algorithms
| Malfunctions detected during operation of the air conditioning system | APN number |
| No cooling | APN 2 |
| Insufficient cooling | APN 3 |
| Increased compressor noise | APN 4 |
| High discharge pressure | APN 5 |
| Low discharge pressure | APN 6 |
| Other malfunctions | |
| No communication with ECU | APN 1 |
APN 1 | No communication with ECU |
Diagnostic guidelines | None |
Make sure that the diagnostic tool is not the cause of this malfunction by testing it while establishing communication with the ECU on another vehicle.
If the device is not the cause of this malfunction, but the dialogue mode is not established with any other ECU of the same vehicle, it is possible that the possible cause is a malfunction of one of the ECUs, which disrupts the operation of the diagnostic K-line.
Disconnect the ECU connectors one by one to determine which one is faulty. If necessary, correct the fault.
Check the battery voltage and perform the necessary work to obtain the proper voltage (9.5V ＜ battery voltage ＜ 17.5V)
Check for 12 V voltage at pin "16" of the diagnostic connector. If necessary, eliminate the fault in the circuit before the fuse. Check for ground on contacts "4" and "5" of the diagnostic connector.
If necessary, correct the fault.
Using a universal contact board, check for breaks and short circuits in the circuits:
- ECU ECM, contact "28" - "ground";
- ECU ECM, contact "33" - "ground";
- ECU ECM, contact "3" - "ground";
- ECU ECM, contact "56" - contact "7" of the diagnostic connector;
- ECU ECM, contact "26" - contact "15" of the diagnostic connector;
- ECU ECM, contact "29" - fuse;
- ECU ECM, contact "30" - fuse.
If necessary, correct the fault.
After troubleshooting, perform a system check using a diagnostic tool.
APN 2 | No cooling |
Diagnostic guidelines | Perform after a complete check of the air conditioning system using a diagnostic tool. |
1. The heater fan does not work
Make sure the heater fan is working properly:
- check the condition of fuses F36 and F39;
- check the serviceability of the additional resistor;
- check the electrical wiring;
- check the serviceability of the heating, air conditioning and ventilation control unit.
If necessary, troubleshoot and replace faulty elements.
2. The compressor does not work
Check the serviceability of fuse F01.
Check for open circuits and short circuits in the circuits:
- heating, air conditioning and ventilation control unit, terminal "5" - terminal "46" of the ECU;
- fuse F01, contact "S" - contact "B3" of the air conditioning compressor relay;
- air conditioner compressor relay, contact "B5" - contact "1" of the air conditioner electromagnetic clutch;
- a/C compressor relay, terminal "B2" - terminal "10" of the ECU;
- air conditioner compressor relay, contact "B1" - contact "A5" of actuator relay;
If necessary, troubleshoot.
Check the serviceability of the compressor electromagnetic clutch.
Replace the compressor if necessary.
3. Insufficient amount of refrigerant in the system
Make sure there is enough refrigerant in the air conditioning system:
- check the refrigerant charge level;
- make sure there are no refrigerant leaks.
If necessary, eliminate refrigerant leaks and restore the refrigerant level.
APN 3 | Insufficient cooling |
Diagnostic guidelines | Perform after a complete check of the air conditioning system using a diagnostic tool. |
1. Contamination of the cabin ventilation air filter
Make sure there is no contamination on the surface of the cabin air filter.
If necessary, clean or replace the cabin ventilation filter.
2. The heater fan does not work
Make sure the heater fan is working properly:
- check the condition of fuses F36 and F39;
- check the serviceability of the additional resistor;
- check the electrical wiring;
- check the serviceability of the heating, air conditioning and ventilation control unit.
If necessary, troubleshoot and replace faulty elements.
3. Slippage of the auxiliary drive belt
Make sure that the accessory drive belt does not slip. Replace the accessory drive belt if necessary.
4. Condenser contamination
Make sure there is no contamination on the surface of the condenser. Clean the condenser if necessary.
5. Insufficient amount of refrigerant in the system
Make sure there is enough refrigerant in the air conditioning system:
- check the refrigerant charge level;
- make sure there are no refrigerant leaks.
If necessary, eliminate refrigerant leaks and restore the refrigerant level.
6. The thermostatic expansion valve (TEV) is faulty
Make sure there is enough refrigerant in the air conditioning system:
- check the correct installation of the TRV;
- check if the expansion valve is dirty or jammed;
- check if the TRV mesh is clogged;
- make sure there is no leak in the thermostatic expansion valve;
- make sure that the expansion valve opens and closes. Replace the expansion valve if necessary.
7. Icing of the evaporator
Make sure the heater fan is working properly:
- - check the serviceability of fuses F36 and F39;
- - check the serviceability of the additional resistor;
- - check the electrical wiring;
- - check the serviceability of the heating, air conditioning and ventilation control unit.
If necessary, troubleshoot and replace faulty elements.
Make sure there is no contamination on the surface of the evaporator.
If necessary, clean the evaporator.
Make sure the receiver-drier is not clogged.
Replace the receiver-dryer if necessary.
Make sure there is no moisture in the system.
If necessary, perform the following procedure:
- drain the refrigerant from the system;
- replace receiver drier;
- drain and fill the system.
8. The receiver-dryer dehydrator is dirty
Make sure the receiver-dryer is not contaminated. Replace the receiver-dryer if necessary
9. Presence of air and non-condensable gases in the system
Make sure there is no air or non-condensable gases in the system. If necessary, release air and non-condensable gases from the system.
10. Compressor valves are faulty
Make sure the compressor valves are in good working order. Replace the compressor if necessary.
After troubleshooting, check the air conditioning system.
APN 4 | Increased compressor noise |
Diagnostic guidelines | Perform after a complete check of the air conditioning system using a diagnostic tool. |
1. Lack or excess of oil in the system
Check the oil level in the air conditioning system. If necessary, top up the oil level to normal.
2. Excessive amount of refrigerant in the system
Check the refrigerant level in the air conditioning system.
If necessary, remove excess refrigerant from the system.
3. Malfunction or low supply voltage of the compressor electromagnetic clutch
Measure the supply voltage of the compressor electromagnetic clutch.
Check the reliability of the connections in the electrical wiring.
If necessary, troubleshoot and replace the compressor.
4. Compressor mounting elements are loose
Make sure that the compressor mounting elements are securely fastened. If necessary, tighten the compressor mounting bolts.
5. Compressor parts are worn or broken
Make sure that there is no wear or damage to compressor parts. Replace the compressor if necessary.
After troubleshooting, check the air conditioning system.
APN 5 | High discharge pressure |
Diagnostic guidelines | Perform after a complete check of the air conditioning system using a diagnostic tool, and in the event that the parameter PR037 "Refrigerant pressure" is above the maximum permissible value (> 6 bar). |
1. High ambient temperature
Make sure that the ambient temperature does not exceed +45°C.
If necessary, test the system in a room with an air temperature of up to 45°C.
2. Excessive amount of refrigerant in the system
Check the refrigerant level in the air conditioning system.
If necessary, remove excess refrigerant from the system.
3. Condenser contamination
Make sure there is no contamination on the surface of the condenser. Clean the condenser if necessary.
4. The engine cooling fan does not work
Make sure the engine cooling system fan is working properly:
- check the fuses for serviceability;
- check the serviceability of the additional resistor;
- check the electrical wiring;
If necessary, troubleshoot and replace faulty elements.
5. The heater fan does not work
Make sure the heater fan is working properly:
- check the condition of fuses F36 and F39;
- check the serviceability of the additional resistor;
- check the electrical wiring;
- check the serviceability of the heating, air conditioning and ventilation control unit.
If necessary, troubleshoot and replace faulty elements.
6. Presence of air and non-condensable gases in the system
Make sure there is no air or non-condensable gases in the system. If necessary, release air and non-condensable gases from the system.
After troubleshooting, check the air conditioning system.
APN 6 | Low discharge pressure |
Diagnostic guidelines | Perform after a complete check of the air conditioning system using a diagnostic tool, and in the event that the parameter PR037 "Refrigerant pressure" is below the minimum allowable value (＜ 2 bar). |
1. Insufficient amount of refrigerant in the system
Make sure there is enough refrigerant in the air conditioning system:
- check the refrigerant charge level;
- make sure there are no refrigerant leaks.
If necessary, eliminate refrigerant leaks and restore the refrigerant level.
2. Low ambient temperature
Make sure that the ambient temperature is not below +10°C.
If necessary, test the system in a room with an air temperature above +10°C.
3. Slippage of the auxiliary drive belt
Make sure that the accessory drive belt does not slip. Replace the accessory drive belt if necessary.
4. Compressor valves are faulty
Make sure the compressor valves are in good working order. Replace the compressor if necessary.
After troubleshooting, check the air conditioning system.