Checking Refrigerating Capacity
TESTING AIR-CONDITIONING SYSTEM FOR REFRIGERATING CAPACITY
Data:
Difference between coldest and warmest max. outlet temperature (cutting-in/cutting-out time of refrigerant compressor):
3°C
Coldest exit temperature from center vent:
3.5 °C,
as of 09/85 5°C
Commercially Available Tools:
1 Vacuum pressure gauge: 1 bar vacuum to 10 bar overpressure
or assembly test device
1 High-pressure gauge: 0-40 bar overpressure
5 Thermometers -20 °c +70 °C
1 Hygrometer
1 Robbi temp 90020 with 4 air temperature measuring probes (4.5 m length):
Kent-Moore (Europe) AG P.O. Box
CH-6340 Baar
Switzerland
1 Therm 2211-1 with measuring point changeover switch:
Ahlborn MeB und Regelungstechnik
EichenfeldstraBe 1-3
D-8150 Holzkirchen bei Munchen
Germany
NOTE: When working on air-conditioning system, pay attention to "Service Precautions".
For a workshop check with regard to complaints about insufficient refrigerating capacity or during a trouble diagnosis on air-conditioning system, proceed according to the following test method which applies to temperatures from +20 °C to +40 °C. Oil check data can be read after 10 minutes of continuous operation.
Test Conditions:
1. Vehicle should not be exposed to sunlight before and during test.
2. Check tension of V-belt for driving compressor.
3. Check auxiliary fan for function, switch on ignition for this purpose and short-circuit the two flat plugs on temperature switch (20). Pay attention to direction of rotation of fan.
4. Engage air-conditioning system and check on sight glass (refer to arrow) in receiver dehydrator whether refrigerant flows free of bubbles shortly after switching-on electromagnetic clutch. Top up refrigerant if insufficient. If more than 200 g of refrigerant are lost, check system for leaks. Refer to "Leak Tests".
5. Set temperature dials (2 and 3) to "MIN" and temperature dial (13) to "MAX".
6. Turn air distribution switch (24) to symbol (image) and air volume switch (4) to 4th blower stage. Open rear passenger compartment vents.
7. Set control lever (19) completely to the left (center nozzle opened).
Attention! On vehicles with modified regulation,
push switch for air conditioning (13),
and switch for fresh air/recirculating air (26) at symbols (arrow).
8. Completely open lateral nozzles (21) for not-heatable fresh air.
9. Close side nozzles (22).
10. Plug one thermometer each into side nozzles and into center nozzles.
11. Attach one thermometer each for fresh air temperature (ambient temperature) approx. 2 m from driver's side.
12. Place one hygrometer into tray of center console.
13. Unscrew closing caps (1) on hose lines (3 and 5). Then connect hose lines of assembly tester to service valves (2 and 4). Make sure that the connecting nipple of the hose lines has a pressure pin in center.
Engine 116/117:
1 Closing cap
2 Service valve (suction end)
3 Hose line from evaporator to compressor
Engine 116/117:
1 Closing cap
4 Service valve (pressure end)
5 Hose line from compressor to condenser
14. Open windows and close vehicle doors.
15. Run engine at approx. 2000/mm.
Engine 110:
1 Closing cap
2 Service valve (suction end)
3 Hose line from evaporator to compressor
4 Service valve (pressure end)
5 Hose line from compressor to condenser
16. After approx. 10 minutes of operation, read values on thermometers and pressure gauges, as well as on hygrometer.
Note: Specified values are max. values and should not be exceeded.
17. Check suction and high pressure in dependence of ambient temperature with reference to table. Check air outlet temperature (mean value of the four cold air outlet temperatures~ also according to data of table. The difference between the coldest and the warmest outlet temperature should not be higher than 3 °C.
Engines 103 and 110:
1) Relative humidity of the air
ta Outside temperature (0 °C)
A Air outlet temperature (0 °C)
B Pressure prior to compressor (bar)
C Pressure after compressor (bar)
D Coolant temperature (°C)
18. Test cutout temperature by inserting a thermo meter into center nozzle Set air volume switch (4) to stage 1. Run engine at approx. 2000/mm. After 3rd cutoff of electromagnetic clutch the air outlet temperature should amount to approx. +4.5 °C, but should not be less than + 3.5 °C.
Attention! If the specified values are not attained, renew temperature dial or temperature sensor or ETR-switch, respectively.
19. The auxiliary fan upstream of the condenser, activated by the coolant temperature and refrigerant temperature/pressure, switches on at higher outside temperatures.
20. Remove hose lines on service valves and close service valves again with closing caps.
21. Take thermometer and hygrometer from vehicle.
Engines 116 and 117:
1) Relative humidity of the air
ta Outside temperature (°C)
A Air outlet temperature (°C)
B Pressure prior to compressor (bar)
C Pressure after compressor (bar)
D Coolant temperature (°C)