A/C - Production Modifications
REF. NO. 83/79TO: OUR MERCEDES-BENZ PASSENGER CAR DEALERS
DATE: February 1994
SUBJECT:
MODEL 140
MODIFICATIONS TO THE A/C SYSTEM
A. AIR FLAPS AND AIR FLAP ACTUATION
B. NOISE REDUCTION
C. BLOWER REGULATOR
D. AUXILIARY FANS
E. REAR A/C SYSTEM
A. AIR FLAPS AND AIR FLAP ACTUATION
As of April 1993, bowden cables have replaced the previously used flex cables to actuate the center and side air vents, allowing a precise and playfree actuation of the air flaps. Removal/installation procedures for the center and side outlet knurled knob panel remain unchanged.
B. NOISE REDUCTION
As of April 1993, the blower motor is attached to its bracket using rubber mounts, thereby isolating any vibration and reducing resultant noise. The support for the heater box between the defroster ducts at the cross brace has been eliminated.
The vacuum elements for the left and right side air outlet diverter flaps (39 and 40, Figure 3) have been eliminated and as a result are not available as replacement parts (See vacuum diagram shown, Figure 6).
For an interim time period, heater boxes with closed-off openings (10, Figure 4) for the vacuum elements were installed in production.
The switchover valve block (Y11, Figure 5) was modified by eliminating the connection (5) for the vacuum elements (39, 40, Figure 3). As a result, the side air outlet diverter flaps are without function, thereby allowing air to travel through the evaporator and heater core, and to the side outlets at all times.
Repair note:
Only the revised valve block is available as a replacement part.
C. BLOWER REGULATOR
The blower regulator (A32n1, Figure 7), part no. 005 820 50 10, is now available as a replacement part.
Note:
Warranty claims for blower motor replacements may be debited if only the blower regulator is defective. Please instruct your responsible personnel accordingly.
Repair note:
When replacing the blower regulator, be certain to clean the mounting surface and apply the supplied heat transfer paste prior to mounting the blower regulator.
For the rear A/C system in Model 140.134, a diode (5, Figure 8) is installed between the rear A/C blower motor (M2/1) and the blower regulator (N29/2) to ensure shut-off.
Repair note:
When ordering the replacement part, please specify that the subject vehicle is a diesel model.
D. AUXILIARY FANS
Auxiliary Fans Switch Points
As of chassis end number 1A 123446, the auxiliary fans are in switched 2 stages (previously 3 stages).
Note:
The auxiliary fans will not engage in stage 1 at ambient temperatures less then 5 °C.
The revised A/C pushbutton control module (N22) recognizes if 2-stage or 3-stage auxiliary fans are installed.
A DTC code of 98 and 99 may be stored in the A/C pushbutton control module (N22) in isolated cases. However, these codes should be ignored provided the auxiliary fans operate properly in both stages.
E. REAR A/C SYSTEM
As of January 1993, an improved rear refrigerant shut-off valve (Y67, Figures 11 and 12) is used in production for noise reduction. It is recognized by a different manufacturer part no. (ND 113 300-1541, previously 1540).
As of chassis end number 1A 128374, the refrigerant injection valve (107, Figure 11) is no longer installed in the evaporator (13) for noise reduction. However, a modified refrigerant injection valve (108) is installed into the rear refrigerant shutoff valve (Y67, Figures 11 and 12).
The pressure line (12, Figure 11) has been insulated to reduce the cooling loss (heat transfer) to a minimum.
Note:
As a result of these changes, the refrigerant fill capacity has also changed (1250g, previously 1400g). In addition, a new Fill Capacity label is installed, part no. 001 989 08 03.
As of August 1993, a revised rear tunnel flap vacuum valve (Y67/1, Figure 13), part no. 140 800 14 78, is installed for noise reduction.