A/C System - Does Not Cool Sufficiently
GROUP 64Heating & Air Conditioning
Bulletin Number
64 10 88
Montvale, NJ
May 1988
Technical Dept.
This Service Information Bulletin supersedes S.I. 64 06 86 (1276). It clarifies the Warranty Status. Please remove and discard S.I. 64 06 86 (1276) from your S.I. binder.
SUBJECT:
1) Evaporator Temperature Sensor Malfunctions
2) Evaporator Temperature Regulator Malfunction
MODELS:
528e, 533i, 535i produced before January, 1985; 633CSi (1983 & 1984) and 635CSi produced before January, 1985.
Complaint:
Insufficient cooling
Cause # 1:
Resistance values of the evaporator temperature sensor are out of specification. Lower than specified resistance readings allow evaporator to "ice up" by delaying compressor OFF signal to evaporator temperature regulator. Higher than specified resistance readings prevent evaporator temperature from getting low enough by sending compressor OFF signal too early to evaporator temperature regulator.
Correction # 1:
Install the improved version of the evaporator temperature sensor with metal tube - P/N 64 51 1 376 699.
If vehicle already has this style of sensor, do not replace the sensor again.
Cause # 2:
Previous evaporator temperature regulator allowed the evaporator temperature to go to O degrees C. The new design regulators are set at 3 degrees C.
Correction # 2:
Check if the Evaporator Temperature Regulator is an updated version. Replace if necessary.
There are 3 different evaporator temperature regulators in use. Identification of the evaporator temperature regulator is as illustrated.
BMW P/N 64 50 1 368 753
A. Regulator has part code 1 368 753-64.5 No paint "X" dots are present. REPLACE REGULATOR.
BMW P/N 64 50 1 376 710
B. Regulator has part code 1 368 753-64.5. with yellow or green paint "X" dot(s). DO NOT REPLACE REGULATOR.
C. Regulator has part code 1 376 710-64.5. DO NOT REPLACE REGULATOR.
Repair Procedure:
Remove trim panel below steering column.
5 Series: Remove center console. This will prevent bending/breakage of the sensor tube.
6 Series: Remove radio.
Install new version evaporator sensor (metal tube).
At the same time check that the evaporator temperature regulator, located on the left side of the evaporator housing, is the improved version.
Quality Control Information:
Before releasing vehicle to customer, perform the following functional test:
1) Start the engine and engage the air conditioner system.
2) Measure the air temperature at the center outlet grill:
a) engine speed 1800-2000 RPM
b) doors closed, windows closed
c) blower speed 11
3) The compressor should:
a) cycle ON at 38-40 degrees F
b) cycle OFF at 34-35 degrees F
4) Allow the system to stabilize (at least 6 ON and OFF cycles).
Warranty Status:
Reimbursable under the provisions of the BMW 3 Year/36,000 Mile New Car Limited Warranty.