HVAC Procedures

This page lists 36 maintenance procedures for hvac (cabin & operator safety), drawn from HIT Srl's internal procedure library extracted from manufacturer service manuals.

HIT Srl supplies cabin, seat and HVAC spare parts for this class of machine.

General guidance only — always follow the operation and maintenance manual for your specific machine.

HVAC

• What is the correct sequence to replace a pry-out cab air vent?

  1. Put the machine in service position.
  2. Use a screwdriver or similar tool to remove the air vent.
  3. Remove the air vent.
  4. Install a new air vent.

• What is the correct sequence to replace a screw-mounted cab air vent?

  Two variants exist: some vents are held only by two screws, while the instrument-panel-mounted vent also has four centre catches and requires removing the instrument panel for warning lights and switches first.

  1. Put the machine in service position.
  2. If the vent is mounted in the instrument panel, remove the instrument panel for warning lights and switches, then squeeze the four catches towards the centre and remove the vent.
  3. Remove the two screws and remove the rest of the vent.

• What is the correct sequence to replace the cab fan on a cab with a floor-mounted heating unit?

  1. Put the machine in service position.
  2. Unplug the electric connections.
  3. Install clamps on the hoses to prevent coolant from running out.
  4. Undo the hose clamps and remove the hoses, using a vessel to collect any coolant that runs out.
  5. Remove the four screws that hold the cab fan to the cab floor.
  6. Remove the cab fan.
  7. Fit in reverse order.

• What is the correct sequence to replace the cab fan on a cab with the fan located behind the wiper motor cover?

  1. Put the machine in service position.
  2. Remove the cover plate holding the wiper motor.
  3. Remove the washer fluid hose and unplug the connector from the wiper motor.
  4. Remove the bolts securing the cab fan to be replaced.
  5. Unplug the connector from the cab fan.
  6. Replace the cab fan.
  7. Fit in reverse order.

• What is the correct sequence to replace the cab fan on a cab with a wing-nut secondary filter cover?

  1. Put the machine in service position.
  2. Undo the wing nuts, remove the cover plates and the secondary filter.
  3. Remove the 15 screws securing the cover plate and remove the cover plate.
  4. Remove the two bolts securing the cab fan to be replaced.
  5. Unplug the connector from the cab fan.
  6. Replace the cab fan.
  7. Fit in reverse order.

• What is the correct sequence to replace the cab heat exchanger on a cab with the exchanger behind the wiper motor cover?

  1. Put the machine in service position.
  2. Remove the cover plate holding the wiper motor.
  3. Remove the washer fluid hose and unplug the connector from the wiper motor.
  4. Remove the fresh air filter and the two screws securing the grille for the fresh air intake.
  5. Empty the cooling system of coolant.
  6. Clamp the hoses to and from the heat exchanger with pinch-off pliers to prevent coolant escaping.
  7. Disconnect the coolant hoses from the heat exchanger under the cab.
  8. Withdraw the heat exchanger from its rest position.
  9. Replace the heat exchanger.
  10. Fit in reverse order.

  Notes:

  • Install clamps on the hoses to prevent unnecessary coolant loss when working on the coolant circuit; wear protective gloves and use a collection vessel for the coolant that runs out.
  • After the work is finished, check the coolant circuit for leaks and check the coolant level, topping up if necessary.

• What is the correct sequence to replace the cab heat exchanger on a cab with a wing-nut secondary filter cover?

  1. Put the machine in service position.
  2. Undo the wing nuts, remove the cover plates and the secondary filter.
  3. Remove the 15 screws securing the cover plate and remove the cover plate.
  4. Empty the cooling system of coolant.
  5. Clamp the hoses to and from the heat exchanger with pinch-off pliers to prevent coolant escaping.
  6. Disconnect the coolant hoses from the heat exchanger under the cab.
  7. Withdraw the heat exchanger from its rest position.
  8. Replace the heat exchanger.
  9. Fit in reverse order.

  Notes:

  • Install clamps on the hoses to prevent unnecessary coolant loss when working on the coolant circuit; wear protective gloves and use a collection vessel for the coolant that runs out.
  • After the work is finished, check the coolant circuit for leaks and check the coolant level, topping up if necessary.

• What is the correct sequence to replace the heating water valve on a machine without electronic climate control?

  1. Put the machine in service position.
  2. Undo the screw and the lock washer that fix the cable to the water valve.
  3. Install clamps on the hoses to prevent coolant from running out.
  4. Undo the hose clamps and remove the hoses, using a vessel to collect any coolant that runs out.
  5. Unscrew the water valve from underneath the cab floor.
  6. Fit in reverse order.

  Notes:

  • After fitting the water valve, check it for leaks and check the coolant level, topping up as necessary.
  • The water valve must be installed with the arrow markings pointing in the direction of coolant travel.

• What is the correct sequence to replace the heating water valve on a machine with electronic climate control?

  1. Put the machine in service position.
  2. Install clamps on the hoses to prevent coolant from running out.
  3. Undo the hose clamps and remove the hoses, using a vessel to collect any coolant that runs out.
  4. Undo the water valve connector.
  5. Unscrew the water valve from underneath the cab floor.
  6. Fit in reverse order.

  Note: After fitting the water valve, check it for leaks and check the coolant level, topping up as necessary.

• What is the correct sequence to replace the air conditioning compressor?

  1. Put the machine in service position.
  2. Open the hood on the right side.
  3. Drain the AC system of R134a refrigerant.
  4. Release the belt tensioner and remove the AC compressor belt.
  5. Undo the hose fittings and disconnect the inlet and outlet hoses from the AC compressor, plugging the fittings to prevent contamination.
  6. Remove the nut and bolt securing the AC compressor.
  7. Empty the oil from the old AC compressor through the inlet/outlet and measure the quantity.
  8. Empty the oil from the new AC compressor.
  9. Refill the new AC compressor with the same amount of oil that was emptied from the old compressor.
  10. Fit in reverse order.
  11. Turn the AC compressor over several turns by hand.
  12. Using vacuum equipment, refill the system with R134a refrigerant and test for leaks.
  13. Check the function of the system.

  Notes:

  • Working on the air conditioning requires special authorisation.
  • Always replace the particle and moisture filter when any work is done on the refrigerant circuit, to prevent contamination and foreign particles entering it.

• What is the correct sequence to replace the AC compressor pulley groove and clutch coil?

  This replacement may be carried out without opening the refrigerant circuit.

  1. Put the machine in service position.
  2. Release the belt tensioner and remove the AC compressor belt.
  3. Remove the screw in the centre of the pulley.
  4. Remove the armature plate and the outer circlip.
  5. Remove the groove.
  6. Remove the three screws that secure the clutch coil.
  7. Remove the clutch coil.
  8. Fit in reverse order.
  9. Check the function of the system.

• What is the correct sequence to replace the air conditioning condenser?

  1. Put the machine in service position.
  2. Drain the AC system of R134a refrigerant.
  3. Remove the outer protective cover from the condenser (four M6 screws).
  4. Cut off the tie wraps and unplug any lighting cables.
  5. Remove the refrigerant hoses from the condenser unit, plugging the hoses to avoid contamination of the refrigerant circuit.
  6. Remove the four screws for the rubber buffers on the condenser.
  7. Separate the condenser from the cover by drilling out the pop rivets.
  8. Pop rivet the cover to the new condenser.
  9. Fit in reverse order.
  10. Using vacuum equipment, refill the system with R134a refrigerant and test for leaks.
  11. Check the function of the system.

  Notes:

  • Working on the air conditioning requires special authorisation.
  • Always replace the particle and moisture filter when any work is done on the refrigerant circuit, to prevent contamination and foreign particles entering it.

• What is the correct sequence to replace the cab's cooling evaporator?

  The exact disassembly steps needed to reach the evaporator vary by cab type (removing the heat exchanger and its cover, or a wing-nut secondary filter cover, or a mounting bracket, depending on cab type), but the refrigerant-handling and evaporator-removal sequence is common.

  1. Put the machine in service position.
  2. Drain the AC system of R134a refrigerant.
  3. Remove the covers, filters and hoses needed to access the evaporator for the specific cab type (e.g. the heat exchanger, its cover plate and grille, or the wing-nut secondary filter cover).
  4. Detach the hoses from the expansion valve, the evaporator outlet connection, and any drain hoses.
  5. Carefully pull out the thermostat's or de-icing sensor's capillary tube/sensor and set it aside, removing its tie wrap and insulation as needed.
  6. Withdraw the evaporator together with the expansion valve from its rest position.
  7. Remove the expansion valve from the evaporator (undo the connection nut and any capillary tube clip).
  8. Replace the evaporator.
  9. Fit in reverse order, using new O-rings and a new particle and moisture filter before refilling the cooling system.
  10. Using vacuum equipment, refill the system with R134a refrigerant and test for leaks.

  Notes:

  • Working on the air conditioning requires special authorisation.
  • Always replace the particle and moisture filter when any work is done on the refrigerant circuit, to prevent contamination and foreign particles entering it.
  • Use new O-rings when installing.

• What is the correct sequence to replace the air conditioning particle and moisture filter?

  1. Put the machine in service position.
  2. Drain the R134a refrigerant out of the AC system.
  3. Remove the screws holding the housing over the condenser, where fitted.
  4. Undo the connections for the coolant hoses and plug them to avoid contamination of the refrigerant circuit.
  5. Undo the connections for the high/low pressure sensor.
  6. Undo the clamps that hold the particle and moisture filter and remove the filter.
  7. Unscrew and remove the high/low pressure sensor.
  8. Install the sensor in the new particle and moisture filter.
  9. Fit in reverse order.
  10. Using vacuum equipment, refill the system with R134a refrigerant and test for leaks.
  11. Check the function of the system.

  Notes:

  • Working on the air conditioning requires special authorisation.
  • The filter is filled with nitrogen under pressure and plugged on delivery to keep it dry; never remove the plugs until immediately before connecting it to the coolant circuit, since open connections let the absorbent material become saturated with moisture within a few hours.
  • The high/low pressure sensor is mounted on the filter's pipe via an integrated valve and can be replaced on its own without draining the refrigerant: disconnect the cable connectors, unscrew the sensor, screw in the new sensor, and refit the cable terminals.

• What is the correct sequence to replace the fresh air actuator motor?

  The disassembly steps needed to reach the actuator vary by cab type (removing the heat exchanger cover and grille, or a wing-nut secondary filter cover and the cab fan), but the actuator itself is unplugged, unscrewed and replaced the same way.

  1. Put the machine in service position.
  2. Remove the covers, filters and components needed to access the fresh air actuator motor for the specific cab type.
  3. Undo the connector and remove the screws or anchorages holding the fresh air actuator motor.
  4. Remove the fresh air actuator motor, and its adapter plate where fitted.
  5. Replace the fresh air actuator motor.
  6. Fit in reverse order.

  Note: Be careful when installing the front of the climate unit, to ensure that no electric cables are pinched or damaged.

• What is the correct sequence to replace the air distribution actuator motor?

  The disassembly steps needed to reach the actuator vary by cab type (accessing the climate unit from inside the cab via interior trim removal, or via a wing-nut secondary filter cover and a front cover plate), but the actuator itself is unplugged, unscrewed and replaced the same way.

  1. Put the machine in service position.
  2. Gain access to the air distribution actuator motor for the specific cab type, removing interior trim and the steering column, or the secondary filter cover and cab-front cover plate, as applicable.
  3. Undo the connector and remove the screws holding the air distribution actuator motor.
  4. Replace the air distribution actuator motor.
  5. Fit in reverse order.

• What is the correct sequence to test the performance of the air conditioning system?

  1. Start the engine at a maximum of 2000-2500 rpm.
  2. Adjust the thermostat to the maximum position.
  3. Open the cab doors.
  4. Start the fan at maximum speed for ten minutes.
  5. Close the cab doors and windows.
  6. Check the high pressure (on the discharge line) and low pressure (on the suction line) with pressure gauges.
  7. Check the temperature inside the cab.

• What checks should be performed before a functional test of the air conditioning system?

  1. Adjust the belt tension.
  2. Check hoses and fittings for leaks.
  3. Check the condenser.
  4. Check all the air ducts.
  5. Check the evaporator.
  6. Check the fans.
  7. Check the air filter.
  8. Check the drier coolant filter (hoarfrosting on the outside indicates internal clogging).

• What is the correct sequence to change the fresh air filter?

  The fresh air filter is located at the front of the cab.

  1. Remove the cover.
  2. Change the fresh air filter.

• What is the correct sequence to clean the condenser?

  1. Put the machine in service position.
  2. Blow the condenser cooler clean using compressed air.

• What is the correct sequence to check the humidity filter?

  1. Put the machine in service position.
  2. Start the engine and let it idle.
  3. Check the colour of the indicator on the humidity filter: blue indication means the humidity filter is ok; grey or pink indication means the humidity filter should be changed.

• What is the correct sequence to change the humidity filter?

  1. Put the machine in service position.
  2. Drain the air conditioning of refrigerant R134a, using the intended draining equipment.
  3. Disconnect hoses and cabling from the humidity filter.
  4. Remove the humidity filter pressure switch from the humidity filter.
  5. Change the humidity filter.
  6. Fit the pressure switch and connect the hoses to the humidity filter.
  7. Check for leaks and refill the machine with refrigerant R134a, using the intended equipment, to the specified volume.

  Notes:

  • Working on the air conditioning requires special authorization.
  • Follow the safety instructions for handling refrigerant R134a to avoid personal injury and environmental damage.

• What is the correct sequence to change the fresh air filter?

  Periodicity: Every 200 hours or when needed.

  1. Remove the filter casing retaining bolts and remove the filter element.
  2. Wash the filter insert with water and detergent or by using a high pressure washer, replacing the insert if necessary.
  3. Reinstall the filter insert.

• What is the correct sequence to check the air conditioning unit?

  Periodicity: If the unit is in continuous operation, every week from early spring to late autumn and during extended periods of high humidity in winter; if used very little during cold, dry winter periods, run the compressor for a few minutes every week to lubricate the rubber hoses, couplings, seals and shaft seal.

  1. Start the engine and start the air conditioner (note the system cannot start below 0°C outdoor temperature, since the low-pressure relay breaks contact).
  2. After 10 minutes of operation, check that no bubbles are visible in the sight glass of the filter-dryer (bubbles should occur only when the compressor is started and stopped); if bubbles are present, have an authorised service mechanic refill the system.
  3. Check that the condenser is not clogged, cleaning the condenser fins and fans with compressed air if necessary.
  4. Change the fresh air filter as necessary.
  5. Check the V-belt tension and the compressor mounting.
  6. Check that the magnetic coupling engages and disengages satisfactorily.
  7. Check that the condensate drain from the cooling element is not clogged, and check for leakage.

  Notes:

  • If the refrigerant hose fails or other refrigerant leakage occurs, switch off the air conditioner immediately.
  • Refrigerant is injurious to the skin and eyes; never release it in an enclosed space, where it may cause asphyxia, and it is forbidden by law to discharge it into the air intentionally.
  • Never carry out welding on a charged refrigeration system or in its vicinity.
  • Only authorised service mechanics are allowed to drain off and fill refrigerant in the air conditioning system, using only the prescribed refrigerant.

• What is the correct sequence to check and performance-test the air conditioning unit?

  The air conditioning does not work below approximately 0°C, since the low pressure switch cuts power to the compressor's magnet clutch when refrigerant circuit pressure is too low.

  Periodicity: Every week during continuous operation from early spring to late autumn, and during long periods of high humidity in winter; if used little in cold, dry winter periods, run the compressor for a few minutes every week to lubricate hoses, couplings, gaskets and axle seals.

  1. Check that the condenser is not clogged, cleaning the fins with compressed air as needed.
  2. Check that the compressor turns on and off without error.
  3. Check that the drain for the cooling element's condensation water is not clogged.
  4. Check for refrigerant leakage, indicated by a dusty, dirty spot where oil and gas often form.
  5. Start the engine, engage the cooling function at maximum, and let the engine run at a minimum of 1500 rpm.
  6. Set the fan to intermediate speed.
  7. After running for 10 minutes, check that no bubbles are visible in the receiver dryer's sight glass (bubbles should occur only when the compressor starts and stops).
  8. Place a thermometer at the air vent closest to the evaporator; after 5-10 minutes, the temperature should be under 10°C.
  9. Feel the hoses and components: those on the pressure side (compressor to expansion valve) should be warm, and those on the suction side (evaporator to compressor) should be cold.
  10. Check the expansion valve for frost or cold temperatures on the intake side, which indicate it is defective or clogged.
  11. Check that the compressor cuts in and out normally by running the cab fan at low speed and the compressor at high rpm, confirming it cuts out near 0°C at the air vents and cuts back in after the temperature rises approximately 3-7°C.

  Note: Parts such as hoses before the condenser can become very hot during long-term operation, with risk of burn injuries.

• What is the correct sequence to check the refrigerant amount via the sight glass?

  Reliable checking through the sight glass can only be performed when the ambient temperature is above approximately 15°C.

  1. Put the machine in service position.
  2. Start the engine and let it idle.
  3. Switch on the air conditioning with maximum cooling and fan.
  4. Check that no bubbles are visible in the sight glass on the particle and moisture filter; bubbles indicate incorrect refrigerant quantity, a defective or clogged condenser, or very high ambient temperature.

• What is the correct sequence to find and repair a refrigerant leak and refill the air conditioning system?

  Work may only be performed on the refrigerant circuit by an accredited company, using special filling equipment.

  1. Turn off the air conditioning.
  2. Check the cooling plant and pinpoint leaks with special leak detection equipment, evacuating and measuring any remaining refrigerant.
  3. Rectify faults, sealing leaks by replacing gaskets, hoses, etc.
  4. Connect the suction pressure gauge's blue hose to the compressor's suction-side service valve, and the pressure gauge's red hose to the discharge-side service valve.
  5. Connect the hoses to the fluid reservoir and the yellow filler/vacuum hose to the nitrogen tube, then open the tube cock and pressure-side cock/valve in sequence to let gas flow through the system and back to the suction side, confirming on the blue gauge; close the pressure-side valve and tube cock afterward.
  6. Conduct leak detection at all hose nipples and connections by applying leak indicator around sealing surfaces and checking for gas bubbles.
  7. Move the yellow hose from the nitrogen tube to the vacuum pump.
  8. Start the vacuum pump, carefully open the suction-side cock, then the pressure-side cock, and hold vacuum suction for at least 30 minutes.
  9. Close both pressure-gauge valves, then turn off the vacuum pump, wait approximately 15 minutes, and check the gauges hold vacuum without change.
  10. Move the yellow hose to the refrigerant cylinder, open its valve, and bleed the yellow hose until pure gas flows out.
  11. Open the suction-side cock and let the gas flow until the gauges indicate the same pressure as in the tube.
  12. Start the compressor and set the cooling thermostat and fan to maximum.
  13. Open the pressure-side valve and let the compressor draw from the cylinder, observing the sight glass until bubbles clear, bypassing the thermostat if it cuts out early, until the correct refrigerant amount is reached.
  14. Close the suction-side valve, then the cylinder valve, disconnect the service hoses from the compressor, and install protective caps.
  15. Check for leaks again.

  Notes:

  • If there is a rupture of a cooling hose or leakage, turn off the unit immediately; refrigerant is dangerous in contact with skin or eyes and must never be released in a closed room, where it can cause asphyxiation.
  • Never weld on or near a closed cooling system.
  • Directly bypassing the compressor's coupling magnet can lead to compressor damage from incorrect refrigerant quantity.

• What is the correct sequence to change the compressor's cooling oil when replacing the compressor?

  The compressor is filled with cooling oil at delivery; under normal conditions the oil should not be changed or refilled.

  1. Drain the defective compressor of oil and measure the quantity.
  2. Drain the new compressor of oil.
  3. Refill the new compressor with the same amount of oil that was drained from the defective compressor.

• What is the correct sequence to change the fresh air filter?

  The fresh air filter is located at the front of the cab.

  1. Put the machine in service position.
  2. Remove the cover and change the fresh air filter.

• What is the correct sequence to clean the condenser?

  1. Put the machine in service position.
  2. Blow clean the condenser's cooler with compressed air.

• What is the correct sequence to check the moisture filter?

  1. Put the machine in service position.
  2. Start the engine and let it idle.
  3. Check the colour of the indicator on the moisture filter: blue means it is ok, grey or pink means it should be changed.

• What is the correct sequence to change the moisture filter?

  1. Put the machine in service position.
  2. Drain the air conditioning of refrigerant R134a using the intended draining equipment.
  3. Disconnect hoses and cabling from the moisture filter.
  4. Disconnect the moisture filter's pressure switch from the filter.
  5. Change the moisture filter.
  6. Fit the pressure switch and connect the hoses to the moisture filter.
  7. Leak test and refill the machine with refrigerant R134a, using the intended equipment, to the specified volume.

  Note: Working on the air conditioning requires special authorisation.

• What is the correct sequence to remove the heater unit?

  1. Remove the front terminal of the heater by gently pulling it with a screwdriver (the heater has 4 air terminals, on both sides and the centre of the front panel).
  2. Remove the air terminal by unscrewing its bolt.
  3. If necessary, remove all other components as indicated.
  4. If air hoses need replacing, also remove the clamps on the air filter side.
  5. Replace or clean the AC filter if necessary.

  Note: Shock hazard: make sure all power supply to the unit is disconnected before performing any work on it.

• What is the correct sequence to install the heater unit?

  1. Install the air terminals by reversing the removal procedure.

• What is the correct sequence to remove the air conditioner unit?

  1. Remove the front terminal of the unit by gently pulling it with a screwdriver (the unit has 4 terminals, on both sides and the centre of the front panel).
  2. If necessary, remove all other components as indicated.
  3. Replace or clean the AC filter if necessary.

• What is the correct sequence to install the air conditioner unit?

  1. Install the AC terminal by reversing the removal procedure.

  Note: Fire hazard: do not use duct tape on or around the fabric discharge air duct collar.

Looking for general maintenance tips and checklists? See Cabin & Operator Safety.