A/C - Diagnosis Supplement For Poor Performance

9229mitsubishi02

NO. TSB-91-55-006

DATE April, 1991

MODEL 3000GT


SUBJECT:

3000GT A/C DIAGNOSIS SUPPLEMENT


PURPOSE

This bulletin provides supplemental air conditioning diagnostic information to be used when the A/C performance on 3000GT vehicles is inadequate. Use this bulletin in conjunction with the diagnostic procedures shown in the service manual when diagnosing complaints of inadequate cooling.


GENERAL INFORMATION

3000GT vehicles use a FX-105VS scroll type compressor which contains an internal bypass valve. The bypass valve is located inside the compressor housing and is not serviceable and its condition cannot be checked visually. It also cannot be removed from the compressor without causing damage to the compressor. If the valve fails, the compressor must be replaced.

The bypass valve is controlled by the control valve. The control valve continually adjusts the position of the bypass valve as a result of system pressure load. This controls the evaporator temperature by varying the flow of refrigerant, bypassing as much as 100%. This bypass feature reduces the need for compressor cycling.

When the bypass valve malfunctions it usually sticks in the compressor housing bore. Depending on the position of the valve when it malfunctions it may force the compressor to operate in minimum bypass (maximum cooling), maximum bypass (minimum cooling), or at some point in between.





In this bulletin is a flow chart showing the proper diagnostic procedures that need to be conducted when a customer complains of "inadequate cooling." The table and charts shown in this bulletin show the various pressures which may be encountered when diagnosing the system, probable cause, and actions which should be taken.





SYSTEM DIAGNOSIS SUPPLEMENT