1987 Chevy Corvette AC clutch won't engage

SELF DIAGNOSIS SYSTEM There are 9 diagnostic modes. Diagnostic mode number 8, for example, is the most commonly used mode for diagnosing this system,. The diagnostic mode is entered while pressing the rear defrost button and then pressing and releasing the manual up button. Once the diagnostic mode is enabled, the mode number may be changed by pressing the warmer button. The Contents of the mode may be displayed by pressing the cooler button. The mode number is displayed preceded by a minus sign. These are the codes: à   Mode # 1 - Program Number à   Mode # 2 - In-Car Thermistor à   Mode # 3 - Ambient Correction à   Mode # 4 - Blower Number à   Mode # 5 - Outside Temperature Thermistor à   Mode # 6 - Feedback Pot Position à   Mode # 7 - Calculated Door Position à   Mode # 8 - System Faults à   Mode # 9 - Software Version Number A system fault is indicated by a flashing annunciator. If there is a problem with the Ambient sensor, In-car sensor, or the Feedback potentiometer, the EXT TEMP annunciator will flash brightly for approximately 60 seconds, upon ignition on. The flashing annunciator will reoccur upon ignition on until the system problem has been corrected. To further investigate a system problem, a diagnostic data "word" can be examined. The diagnostic data "word" is displayed by entering diagnostic Mode # 8. The diagnostic data "word" is a number that indicates the failure mode. Faults can be determined by evaluating the Binary Equivalent of the diagnostic data word displayed. A "1" in a column is an indication of an error of that category. The Diagnostic Mode can be exited by depressing any mode button on the ECC control face. RETRIEVING STORED TROUBLE CODES The terms "Enter Diagnostics" and "exit diagnostics" will be used periodically throughout this section. Follow step 1 of Entering Diagnostic Mode procedure when instructed to "Enter Diagnostics". Use Exiting Diagnostic Mode procedure when instructed to "Exit Diagnostics". Use this procedure to withdraw all stored codes, and to determine which of the codes are "hard" and which are "intermittent". NOTE: Complete testing and diagnosis information for the Corvette was not provided by the manufacturer. Only diagnostic mode entry, program mode number sequence, and diagnostic mode exit procedures are provided.
Entering Diagnostic Mode 1. Turn ignition on. Depress "OFF" and "WARMER" buttons on 2. After the display, "8.8.8" ends the segment check Fig. 4: CCP Stored Code Operation Courtesy of GENERAL MOTORS CORP. 3. Progressively higher numbered ECM codes, if present, will be displayed consecutively for 2 second intervals until the highest code present has been displayed. During this first cycle of ECM codes, any trouble code stored in computer memory will displayed on the "Data Center". If no ECM trouble codes are stored, "..E" display will be bypassed. 4. If ".E.E" is displayed this indicates the beginning of the second cycle of ECM trouble codes. On the second cycle, only "hard" codes will be displayed. Hard codes indicate a currently present malfunction. Codes displayed in the first cycle and not the second are "intermittent" codes. If all ECM codes are intermittent, "E.E." display will be by-passed. 5. After all ECM codes have been displayed, or if no codes were present, code ".7.0" will be displayed. Code ".7.0" indicates that the system is ready for the next diagnostic feature to be selected. 6. If a code "51" is displayed, it will display continuously until the diagnostic mode is exited. During the display of code "51", none of the other diagnostic features will be possible. Status Light Display While in diagnostic mode, status lights on CCP control head indicate status of various operating modes. Different modes of operation are indicated by the light, being on or off. The status lights and modes they represent are as follows: "AUTO" This light is illuminated when ECM is operating in "closed loop" fuel control mode. This light will glow after coolant and oxygen sensors have reached operating temperature. "ECON" This light is illuminated when oxygen sensor indicates to ECM that a rich exhaust condition exists. NOTE: If all segments of readout do not display, diagnosis should not be attempted, as this could lead to mis-diagnosis of the system (Code "34" appears as "31", etc.) If any of the segments are inoperative, the CCP control head must be replaced. NOTE: Trouble codes may appear prefixed with an "E" or "F" to designate which computer (ECM) detected the fault. The "E" codes will appear first. This light should flash on and off during warm steady throttle operation. "OFF" This light indicates that throttle is closed. This light should be off whenever throttle is applied. "FRONT DEFOG" This light is illuminated whenever ECM is commanding VCC to engage. This indicator only signals that VCC is enabled or disabled by the ECM. Actual operation depends on the integrity of VCC system. "REAR DEFOG" This light indicates when ECM senses that fourth gear switch is open. Light should only be on during fourth gear operation. "OUTSIDE TEMP" This light is illuminated whenever the BCM is commanding the ECC (A/C) compressor clutch to engage. This light only indicates whether clutch is enabled or disabled by BCM. Actual operation depends on the integrity of compressor clutch system. "AUTO FAN" Status indicator is turned on whenever feedback signal from the cooling fans control module to BCM indicates that fans are running. This light should be off when the cooling fans are off. "HI FAN" This light is illuminated whenever BCM is commanding "UP-DOWN" mode door to divert air flow up away from the heater outlet. This light will be off whenever climate control system is in "heater" or "normal purge modes. "LO FAN" This light is illuminated whenever BCM is commanding "A/C-DEF" mode door to divert air flow to A/C outlets as in "A/C" or "normal purge" modes. This light will be off whenever ECC (A/C) system is in "heater", intermediate," "defrost" and "cold purge" modes. " °F" This light is illuminated whenever BCM senses that refrigerant low pressure switch is open. This light is illuminated when ambient temperature falls below approximately -5 °F (-15 °C) due to pressure-temperature relationship of refrigerant system is fully charged and being controlled properly. " °C" This light is illuminated whenever BCM is commanding heater water valve to block water flow through heater core. This light should remain off except when air-mix door is being commanded to the "Max. A/C" position (0 percent). Exiting Diagnostic Mode The cycle of trouble code displays may be exited at any time. To do so, simply press the "AUTO" ECC function key. Diagnostics may also be exited by turning ignition switch off for 10 seconds. Either method will take ECC panel out of diagnostic mode, but will not clear any trouble codes. Original temperature setting should appear on ECC panel. Clearing ECM Trouble Codes After system is diagnosed and repaired, all stored trouble codes may be cleared from ECM/BCM memory. To clear ECM codes, enter diagnostic mode and depress "OFF" and "HI" buttons on CCP panel at the same time. Hold buttons until "E.0.0" appears.
4/24/2010 ...
Run this and see if any codes are stored...
COMPRESSOR CUT-OFF SWITCH Vehicles are equipped with a Wide Open Throttle (WOT) Cut-Off switch. It disengages the compressor when maximum acceleration is required. This action also reduces the heat load on the cooling system by eliminating the additional compressor load when going up steep grades. The switch is located on the accelerator pedal bracket and interrupts the compressor drive signal being sent from the programmer to the power module.

Check #6 fuse.