Checking Refrigerating Capacity (Short Test)
TESTING REFRIGERATING CAPACITY OF AIR CONDITIONING SYSTEM (QUICK TEST)Data
Difference between coldest and warmest outlet temperature max. 3°C
(cutting out/cutting in time of refrigerant compressor)
Coldest air outlet temperature out of center nozzle (center outlet) 3.5°C
Conventional tools
2 thermometers -20°C to +70°C
Digital temperature measuring instrument with 4 measuring probes
Robbi temp 90020
Air temperature measuring probe 90023
(4.5 m cable length)
Supplier e.g.:
Switzerland: Kent-Moore (Europe) AG
P.O. Box, CH-6340 Baar
Germany: Fa. Kalte-Fischer
Postfach 266. Augsburger Str. 289-291
D-7000 Stuttgart 60
Digital temperature measuring instrument with 4 measuring probes
Therm 2263-2
Measuring point changeover switch with 4 connections 2235-4
Air temperature measuring probe W 453-5
(3m cable length)
Supplier e.g.:
Germany: Ahlborn Mes- und Regelungstechnik in der Eichenteldstrase 1-3, D-8150 Holzkircher
Quick test
For air conditioning systems free of complaints. Test after minor repairs, longer stationary periods or the like.
Test procedure for ambient (interior) temperatures from +20 °C to +40 °C. Check values can be read after approx. 5 minutes.
Test conditions
1 The vehicle should not be in the sunlight during test.
2 Check tension of V-belt for compressor drive.
3 Check auxiliary fan for function, while switching on ignition and bypassing the two flat plugs on pressure switch (19), or connecting 1-pin connector of 100 °C switch to ground. Pay attention to direction of rotation of auxiliary fan (clockwise).
4 Check fluid level in air conditioning system; for this purpose, pull one line from pressure switch (22), run engine at idle (>700/mm) and engage air conditioning system by means of function selection "max dehumidification". Clean sight-glass (arrow) in receiver drier. Watch sight-glass while simultaneously plugging line on pressure switch (22). Refrigerant should rise shortly after switching on electromagnetic clutch and should then flow free of bubbles (i.e. refrigerant no longer visible).
Attention! In the event of major refrigerant losses or an empty system, the voltage for the refrigerant compressor is interrupted by the pressure switch (22). When the pressure increases to 0.6 bar above the cutout pressure, the circuit is again closed.
5 Check whether the heater shuts off in selector wheel position "MIN". For this purpose, let engine run at idle and engage air conditioning system with function selection "normal A/C". Set temperature selector wheel (a) to "MIN". Refrigerant compressor should be on after 20 seconds at the latest.
Note: If the refrigerant compressor is not engaging, bridge lines from pressure switch (22) and check fluid level according to item 4. If the refrigerant compressor is still not engaging, test entire system with socket box and volt-ohmmeter. On model 201.024 starting model year 85 and on model 201.122 there may be an additional fault on compressor cutout.
Testing
1 Set temperature selector wheel (a) to "MIN".
2 Switch on function selection "center vents" of pushbutton switch (b) and function selection "max dehumidification" of switch air conditioning system (c).
3 Set blower switch (15) to 2nd blower stage.
4 Open center and side outlets and switch off switch (26) (fresh air).
5 Insert one thermometer into lefthand or right- hand center outlet (25).
6 Position one thermometer for ambient temperature (room temperature) approx. 2 m from driver's side outside vehicle.
7 Open window and close vehicle doors. Run engine at approx. 2000/min.
Diagram for model 201.024
Ta = Outside temperature °C
8 After approx. 5 minutes read air outlet temperature at center outlet and outside temperature and compare with data of diagrams.
Diagram for model 201.122
Ta = Outside temperature °C
Attention! The air outlet temperature on center outlet should not be below +3.5 C. If the value is less than specified, check temperature sensor of air conditioning system and renew, if required, or test electric lines from temperature sensor for air conditioning to pushbutton switch unit for ground short. If there is no remedy, renew pushbutton switch unit.