Checking the health and maintenance of heating and air conditioning systems (Nissan Maxima A32)

Warning! The air conditioning system is under constant high pressure. Never disconnect refrigeration lines or remove any system components without first discharging the system. Discharging the air conditioning system must be done by an experienced technician in a car service workshop. Always wear safety glasses when disconnecting refrigeration lines!

When replacing air conditioning system components, a certain amount of replacement refrigeration oil will be required to fill the volume of the new unit. Use only oil suitable for use in R-134a systems (read the container label carefully). Please note that seals designed for use in R-12 oil filled systems are not suitable for this application.

Service

1. The following checks should be performed on a regular basis to maintain the air conditioning system in good condition:

• a) Check the condition of the compressor drive belt. If defects or signs of wear are detected, replace it (see Chapter Settings and ongoing maintenance);
• b) Check the tension of the drive belt and adjust it if necessary (see Chapter Settings and ongoing maintenance);
• c) Check the refrigeration line hoses for cracks, swelling, signs of hardening and aging of the rubber, assess the condition of the nipple connections. Replace defective components;
• d) Check the condenser heat exchanger plates for insect remains, old leaves and other debris stuck between them. If necessary, clean the gaps with a thin brush or blow them out with compressed air;
• e) Check the system charge level;
• f) If there are fluid leaks in the area of the instrument panel or on the mats, check the patency of the evaporator drain pipe.

2. The air conditioning system should be turned on for at least 10 minutes at least once a month (even in winter). Long-term inactivity of the K/V leads to hardening and failure of the sealing rings and cuffs of the connecting tract.



3. Due to the complexity of the system design and the need to use special equipment, its maintenance, in-depth diagnostics and repairs are beyond the skill level of the average amateur mechanic and must be performed in a car service workshop. The car owner is only competent to perform the simplest checks and replacements listed below in this Section.

4. The most typical reason for malfunction of the air conditioner is a decrease in the charge level of the refrigeration oil.

5. The following simple tests will quickly identify signs of low refrigerant levels.

Examination

1. Warm up the engine to normal operating temperature.

2. Turn on the air conditioner to maximum cooling capacity. Select the maximum fan speed. Open the doors to avoid cyclic shutdowns of the system when cooling the closed air volume in the cabin.

3. After the system reaches operating temperature, feel the two tubes connected to the evaporator on the engine compartment bulkhead.



4. The thinner tube going to the evaporator from the condenser outlet should be fairly cool to the touch. The thicker tube going from the evaporator outlet back to the compressor should be a little more (by 2 - 6 degrees) colder. If the outlet pipe is noticeably warmer than the inlet pipe, the system needs recharging. Insert a thermometer into the outlet air duct through the central deflector on the instrument panel. When the air conditioning is on, the temperature of the air coming out of the deflector should be 19 - 22 degrees lower than the ambient temperature (up to 4.5°C). In very hot weather (40°C), an increase in the outlet temperature to 15.7°C is permissible, but not more. If the air conditioner does not provide the required intensity of air cooling, the system should be recharged. For a more detailed diagnosis of the system's condition, the car should be driven to a specialized workshop.



5. If the cooling intensity of the air supplied to the cabin is insufficient, the system probably needs recharging.

6. If there are signs of complete system failure, check the proper functioning of the compressor clutch.

7. Observe the front side of the compressor and ask an assistant to turn on the A/C. The clutch should make a distinct click and its central part should start to rotate, otherwise, turn off the engine and disconnect the system pressure switch. Use a jumper wire to short-circuit the connector terminals and turn on the air conditioner again. If the system now starts to function properly, therefore the pressure in it is excessively high or low, drive the car to a service station.

8. If the clutch still does not engage, check the condition of the corresponding fuses in the fuse box located in the vehicle interior.

9. Remove the compressor clutch relay from the mounting block located in the engine compartment and check its proper functioning (see Chapter On-board electrical equipment). With the relay removed and the ignition on, check that the power supply to the two relay terminals in the mounting block is working properly (see the electrical connection diagrams at the end of Chapter On-board electrical equipment).

10. Using a jumper wire, connect the power terminal of the compressor clutch relay to the mounting block (see electrical connection diagrams) to the appropriate clutch terminal - the clutch should click. If there is no click, disconnect the wiring from the clutch and check for proper power supply to its connector. Check for proper grounding of the black wire terminal of the connector. If the wiring is OK, the compressor clutch assembly should be replaced.



11. If all components and wiring are in order and the system is charged to the required level, the vehicle should be taken to a service station for diagnostics and repair of the PCM.

12. More detailed diagnostics of the air conditioning system is beyond the skill level of the average amateur mechanic and should be left to car service specialists.

Adding refrigerant

Caution! Only R-134a refrigerant oil should be used to charge the air conditioning system of the vehicles covered in this Manual.

1. Prepare a standard R-134a charging kit (ask in car accessories stores). The kit includes a 12-ounce can of refrigerated oil (ounce), a valve nozzle, and a length of hose that connects between the valve and the low-pressure part of the refrigerator path. Since one can of oil may not be enough to fully charge the system, it makes sense to buy a couple at once, just in case. Make sure that the oil in at least one of the cans is tinted red, which will allow you to quickly identify refrigerant leaks if any occur.

Attention! Never fill the system with more than two cans of refrigerant!

2. In accordance with the manufacturers instructions, connect the charging kit to the LOW PRESSURE portion of the refrigeration line.



3. Close the valve on the adapter and screw the latter onto the head of the can, having first checked that the sealing ring/rubber gasket is present.

Attention! Be sure to wear protective glasses!

4. Remove the dust cap from the low-pressure part of the refrigeration line and connect the charging kit hose equipped with a quick-connect connector to it.

Attention! The design of the nipple units does not allow the set to be connected to the high-pressure part of the tract.

5. Warm up the engine to normal operating temperature and turn on the A/C. Make sure that the charging kit hose does not come into contact with the engine cooling/air conditioning fan blades or other moving components in the engine compartment.

Note: The system must be charged with the compressor running. If the compressor clutch disengages, the system must be switched to maximum cooling capacity and all cabin doors must be opened.

To prevent the compressor from shutting off during charging, disconnect the connector from the low pressure switch (some models use a combination low/high pressure switch) and bridge it with a paper clip or a piece of stiff wire.

6. By rotating the valve nozzle, pierce the head of the cylinder, thereby opening the supply of refrigerant (you should hear the characteristic sound of escaping gas). During the entire charging process, hold the can strictly vertically, shaking it from time to time. Between charging series, make a pause necessary for the system to stabilize.

Note: Never fill the system with more than two refrigerant canisters! To prevent the canister from freezing during filling, wrap it in a towel soaked in warm water.

7. If you have an accurate thermometer at hand, insert it through the deflector into the central air duct of the air conditioner and monitor the temperature of the air supplied to the cabin.

8. When the can is empty, close the valve and disconnect the hose from the low-pressure fitting of the system. Immediately put the dust cap on the fitting.

9. Disconnect the valve nozzle from the cylinder, if necessary, move it to the second cylinder and continue filling. After completing the procedure, place the unfinished cylinder vertically on the rack and use it to recharge the system as needed.

Heating system

1. Wetting of the carpet on the floor under the heater heat exchanger, or steam escaping through the air duct deflectors indicate heat exchanger leaks. Remove the heat exchanger (see section Removal and installation the heater heat exchanger) and replace it with a new one (the heater heat exchanger is not subject to repair).

2. If the heater does not provide adequate heating of the air supplied to the passenger compartment, the reason for such failure may be one of the following:

• a) The thermostat is stuck open, preventing the engine coolant supplied to the heater heat exchanger from heating up to normal temperature. Replace the thermostat (see section Checking the correct operation and replacing the thermostat);
• b) There is a blockage in the cooling tract, which blocks the supply of coolant to the heater heat exchanger. Feel the hoses connected to the pipes on the rear bulkhead of the engine compartment - both of them should be hot, otherwise the tract is blocked (the hoses, heat exchanger, or heater control valve are blocked). Disconnect the hoses and perform a reverse flow flush of the heat exchanger. After disconnecting, flush both hoses as well;
• c) If it is not possible to restore the patency of the heat exchanger by flushing, it should be replaced (see section Removal and installation the heater heat exchanger).

Eliminating Air Conditioning Odors

1. Unpleasant odors that often occur when the air conditioner is turned on are caused by the formation of mold colonies on the evaporator heat exchanger plates. A warm, humid environment creates favorable conditions for the emergence and development of fungal microorganisms.



2. Access to the evaporator heat exchanger on most models is extremely limited. The procedure for guaranteed complete mold removal, performed in a car service workshop, is quite labor-intensive, time-consuming and requires the use of strong disinfectants. In principle, a fairly effective treatment can be performed at home by the car owner himself.

3. Special disinfectants in aerosol packaging designed for servicing air conditioning systems can be purchased at almost any car accessory store. It should be remembered that the price of the product is usually directly proportional to its effectiveness. Switch the system to closed air circulation mode and turn on the heater fan at maximum speed for ten minutes. In order to dry the system, turn on the heating at maximum intensity. Disconnect the wiring from the compressor in order to prevent it from operating.



4. The product is usually supplied through a long hose. Remove the resistor assembly of the heater fan drive electric motor (see section Removal and installation the electric motor of the heater fan drive), insert the nozzle of the feeder into the resulting hole and move it to the left, directing it at the evaporator heat exchanger. The product is fed in accordance with the manufacturer's instructions. Try to treat the entire surface of the heat exchanger as completely as possible. The duration of each treatment cycle and the intervals between series must be indicated on the container label.

5. The best preventive measure against the formation of mold colonies in the evaporator heat exchanger is to regularly check the patency of the drain tube, as well as briefly turn on the condensate removal mode after each long trip with the air conditioner running in order to dry the evaporator.

Climate control system

The optional equipment of Nissan Maxima cars may include a climate control system. The system is controlled by its own processor, which receives the necessary input data from various information sensors. Like the PCM, this processor includes a self-diagnostic unit, which provides the ability to quickly find and fix faults. The operator selects the desired temperature mode and sets it using a special handle on the control panel. Then the system begins to automatically maintain the set air temperature in the car, regulating the supply of cold and / or warm air accordingly. The speed mode of the fan is also controlled by the microprocessor through a series-connected controller, which in this case replaces the resistor assembly. Full diagnostics of failures and repair of the climate control system is beyond the qualifications of the average amateur mechanic. However, the processor is equipped with an on-board self-diagnostic device with the ability to display fault codes.