A/C Performance Test (83/30)

A/C PERFORMANCE TEST

TECHNICAL SERVICE BULLETIN

A/C PERFORMANCE TEST

Model(s): 1981 Mercedes-Benz 280 E, 280 CE; 1981-1983 Mercedes-Benz 240 D, 380 SEL; 1981-1985 Mercedes-Benz 300 D, 300 CD, 300 SD, 300 TD; 1982-1983 Mercedes-Benz 380 SEC; 1982-1985 Mercedes-Benz 380 SL; 1984-1985 Mercedes-Benz 380 SE, 500 SEC, 500 SEL; 1984-1988 Mercedes-Benz 190 E; 1984-1989 Mercedes-Benz 190 D; 1986-1987 Mercedes-Benz 300 SDL; 1986-1989 Mercedes-Benz 560 SL; 1986-on Mercedes-Benz 300 E, 420 SEL, 560 SEC, 560 SEL; 1987-1989 Mercedes-Benz 260 E; 1988-on Mercedes-Benz 380 SE, 380 SEL; 1990-1991 Mercedes-Benz 350 SDL; 1991 Mercedes-Benz 350 SD, 190 E

Group: 83 - Climate Control System, Automatic/Tempmatic A/C

Bulletin No.: 83/30

Date: July 1991

SERVICE INFORMATION

MODEL 107 STARTING MODEL YEAR 1982

MODELS 123 AND 126 (EXCEPT.024/025) STARTING MODEL YEAR 1981

MODELS 124.026/030 STARTING MODEL YEAR 1986

MODEL 201 (EXCEPT.029) STARTING MODEL YEAR 1984

The A/C Performance Test described below supersedes the test described in the Education for Excellence manual and also in the service microfiche.

For further information regarding working on the A/C system, please refer to S.I. MBNA 83/25 , October 1987.

TEST CONDITIONS

1. Do not allow vehicle to sit in direct sunlight prior to and during test.
2. Check condition of compressor V-belt.
3. Check function of auxiliary fan by turning ignition key to "ON" and bridge both pins on the refrigerant high pressure switch, auxiliary fan (S32). The fan should engage in low fan speed.

   1. 3.1
      Check function of auxiliary fan in high speed. Depending on model and model year, bridge switch (see table) with ignition "ON". Fan should engage in high fan speed. Also observe for correct direction of rotation of fan (clockwise as viewed from front of vehicle).
      EFFECTIVE SERIAL NUMBER
      
      

      Model	Model Year	Bridge Switch: (1)
      107	starting 1986	S25/5
      124	1986 & 1987 starting 1988	S25/5 B11/7
      126	1986 & 1987 starting 1988	S25/5 B11/7
      201.034	starting 1986	S25/5
      201.0	starting 1985 starting 1988	S25/4 B11/7
      201.1	starting 1985 starting 1988 location.	S25/4 B11/7
      (1) = Refer to respective ETM for switch

4. Check fluid level of receiver-drier.

   1. 4.1
      Disconnect one wire from refrigerant pressure switch (S31/1).
   2. 4.2
      Run engine at idle and engage A/C system at pushbutton control panel.
   3. 4.3
      Observe sight glass and reattach wire to pressure switch (S31/1). Shortly after compressor clutch switches on, the fluid level must rise and the refrigerant should flow past the sight glass, free of bubbles (the refrigerant will not be visible). If bubbles are visible, check system for leaks.
5. Measure and record shop temperature six feet from driver's door (ambient temperature).

   1. 5.1
      Determine if relative humidity is closer to 40% (normal) or 90% (hot, humid or raining).
6. MODEL 201 ONLY: Pull connector from S31 and connect to ground so that auxiliary fan is running during entire test.
7. Remove cap from service valve on suction and discharge line. Connect pressure gauge to service valves. Assure that the hose connection fittings are equipped with a pressure pin in the center of the fitting. Close engine hood against rear seal.
8. Open center and left/right air outlets. On model 126 vehicles, close the side air outlets and open air outlet in rear passenger compartment console.
9. Place thermometer in center air outlet.
10. Open all windows and close all doors.

The following test is designed to confirm the operating efficiency of the air conditioning system.

Be certain to have performed all the necessary test conditions before actually performing the test.

AIR CONDITIONING SYSTEM OPERATING EFFICIENCY TEST

Function	Model 123, 124, 126, 107	Model 201
Engine Speed	2000 rpm	2000 rpm
Temperature Wheel	MIN	MIN
Blower Speed	MAX Fan Speed	MAX
Push Buttons	Normal setting button and press Air Recirculation button	Normal Cooling/ Fresh Air Ventilation button
Compressor Button	(not applicable)	Dehumidifying button
Running Time	Ten minutes	Ten minutes

Compare the temperature and pressure values obtained from the test to the values listed in the charts. Find the measured shop temperature (ambient temperature) in the left most column and read the values across, according to the approximate relative humidity (40% or 90%).

POSSIBLE CAUSES FOR DIFFERENCES IN VALUES

CHECKING ON/OFF COMPRESSOR CYCLING

Function	Model 123, 124, 126, 107	Model 201
Engine Speed	2000 rpm	2000 rpm
Temperature Wheel	MIN	MIN
Blower Speed	MAX Fan Speed	Speed I
Push Buttons	Normal setting button and press Air Recirculation button	Normal Cooling/ Fresh Air Ventilation button
Compressor Button	(not applicable)	Dehumidifying button

All doors and windows are to be closed during this test.

Read center outlet temperature after the third time that the compressor has cut-out.

Model 123, 124, 126, 107	Model 201
Approximately 39°F (4°C) but no less than 37°F (3°C)	No less than 38°F (3.5°C)

Maximum allowable temperature difference between compressor cycling on/off is 5°F (3°C).