Heating and Air Conditioning: Service and Repair

Assembly Work on the Air-Conditioning System





Service Unit SECU 134

NOTE: The manufacturer's operating and repair instructions must be observed when carrying out all work on the service unit.


Assembly Work Involving the Refrigerant System

NOTE:
- The safety regulations must be observed during all work on the refrigerant system. See "Safety regulations when handling refrigerant R134a"
- During all work on the air-conditioning system which necessitates opening the refrigerant system, the system contents must first be disposed of correctly.
- Dirt and moisture must be kept out of the air-conditioning system's pipe system.
- Thorough cleanliness must be ensured during all work.
- System components must never be cleaned on the inside with hot steam.
- Use only nitrogen for cleaning purposes.
- When replacing a component, all openings must be closed off with suitable plugs.


General Assembly Sequence

NOTE:
- Pay attention to sealing rings when disconnecting or connecting the hose connections.
- The charging valves are located in the area of the front right spring strut.




-A- = high pressure -B- = low pressure

1. Remove refrigerant by suction.
2. Remove faulty part.
3. Evacuate.
4. Check the system for leaks.
5. Rinse with refrigerant.
6. Empty the system by suction again.
7. Evacuate.
8. Fill.


Removing Refrigerant By Suction and Cleaning





NOTE: Close all valves before carrying out each work step.

- Drain off refrigerant from the filling cylinder into a refrigerant bottle (approx. 50%)


Cleaning the Refrigerant




Illustration


Draining Off Old Refrigerant Oil




Illustration


Evacuating





Evacuation time at least 15 minutes.


Topping Up With New Refrigerant Oil




Illustration


Filling Via the High-Pressure Side





NOTE: Before carrying out internal suction removal of the SECU, the hand valves on both suction lines must be closed.

- After using the SECU, perform internal suction removal.


Refilling the Air-Conditioning System

NOTE: In the event of insufficient refrigeration performance, remove the refrigerant by suction, top up with the stipulated quantity and check the system for leaks.

1. Remove the refrigerant by suction using the service unit
2. Determine the refrigerant oil quantity after the refrigerant has been removed by suction.
3. Fill up with new refrigerant oil.
4. Evacuate.
5. Fill with the stipulated amount of refrigerant.
6. Check the system for leaks.


Distribution of the Oil Quantity In the Refrigerant Circuit

NOTE:
- Oil removed by suction must be returned to the system.
- Refrigerant oil removed from a previously run air-conditioning system may no longer be used (special-category waste).
- After the refrigerant has been removed by suction and a component has been replaced, the oil quantity must be determined and topped up by the quantity remaining in the removed component.


Oil quantity
Total oil quantity 195 ± 15 cubic cm

After suction removal from the system, the following quantities remain in the:

Condenser (2 x 20 cubic cm) approx. 40 cubic cm
Evaporator approx. 30 cubic cm
Fluid tank with lines approx. 30 cubic cm
Compressor approx. 50 cubic cm
Circulating oil quantity in the refrigerant circuit approx. 60 cubic cm