A/C - Belt Lock Controller Operation/Troubleshooting
NO.: TSB-91-55-015DATE: November, 1991
MODEL 1992 Diamante LS
SUBJECT:
BELT LOCK CONTROLLER OPERATION/TROUBLESHOOTING - SERVICE MANUAL SUPPLEMENT
PURPOSE
This bulletin provides service technicians with A/C belt lock controller general operation and procedures to be followed if you suspect A/C compressor lock-up.
BELT LOCK CONTROLLER OPERATION
In Diamante LS vehicles, both the A/C compressor and the alternator are driven by the same belt. If the A/C-alternator belt is loose, it may slip when the A/C is turned on. Belt slippage affects A/C performance and alternator output. The belt lock controller's function is to turn off the A/C compressor clutch if the belt slips or the compressor locks-up.
By using output from the A/C compressor revolution pick up sensor, the belt lock controller calculates the actual A/C compressor speed relative to engine speed (see block diagram). If the controller senses an A/C compressor clutch slipping condition (70% slip for 3 seconds or more), the controller switches oft the A/C compressor clutch. When the controller switches the A/C compressor oft, the NC switch indicator light begins blinking. If the A/C-alternator belt should break or if the compressor does not turn, the controller switches off the compressor clutch and causes the indicator light to blink.
The belt lock controller is located inside the vehicle near the evaporator assembly.
Mounted on the A/C compressor is the Revolution Pick-up sensor.
TROUBLESHOOTING INFORMATION A/C SWITCH INDICATOR BLINKS
LOCKED-UP A/C COMPRESSOR DIAGNOSIS
1. Disconnect the A/C compressor electrical connector.
2. Using an external 12V battery, connect a jumper wire to ground the external battery negative terminal to the compressor. Then connect another jumper wire to the external battery's positive terminal. Momentarily touch the jumper wire to terminal # 1 on the compressor side of the connector.
The magnetic clutch can be considered OK if a "click" comes from the clutch. If there is no "click" check the magnetic clutch using procedures shown in the service manual.
3. Connect the positive jumper wire to the compressor side terminal # 1. While watching the compressor clutch for movement, turn the engine over by hand using a 1/2" drive socket extension and ratchet on the crankshaft bolt.
CAUTION:
Do not use the starter to crank the engine. If the compressor is locked-up, cranking the engine can break the belt.
If the compressor pulley does not rotate, replace the compressor. Refer to the service manual for compressor replacement instructions.
BELT LOCK CONTROLLER SYSTEM BLOCK DIAGRAM