DESCRIPTION
| CAUTION | When discharging air conditioning system, use only approved refrigerant recovery/recycling equipment. Make every attempt to avoid discharging refrigerant into the atmosphere. |
Electronic Climate Control (ECC) is used. The temperature control system provides automatic regulation of vehicle interior temperature regardless of the outside conditions. Temperature and mode of operation are selected by push buttons on control panel. The "COOLER" and "WARMER" mode buttons select temperature, while control modes are selected by one of 6 (7 with rear defroster) buttons across bottom of control panel.
A modulator A/C-heater case encloses the evaporator, heater, blower, and doors in one assembly. The CCOT (Cycling Clutch Orifice Tube) refrigeration system is the same as described for other General Motors vehicles with manual A/C-heater systems, with the following exception
- A compressor cycling switch is used.
OPERATION
| Control Settings | Temp | System Should Operate As Follows |
|---|---|---|
| FRT DEF | 90° | Warm air should be delivered from defroster outlets at a fixed high blower speed. Minor floor bleed from heater outlet. |
| HI | 90° | Warm air should be delivered from the heater outlet with only a small amount from the defroster outlets. The blower should stay at high speed. |
| AUTO | 75° | After a short delay, the blower speed should gradually decrease. Discharged air should become cooler. Depending on the temperature in the work area, the air delivery mode should change to A/C outlets from the heater outlets. The intermediate delivery mode is defrost when this transition occurs. |
| AUTO | 60° | Blower speed should increase to a fixed high value. Discharged air should become maximum cold. The air inlet door should slowly open (signalled by blower noise increase). |
| LO | 60° | After a short delay, the blower speed should gradually decrease to a very low value. The discharged air should remain cold and come from the A/C outlets. The air inlet door should slowly close. |
| ECON | 60° | The A/C compressor should be off. Blower speed should gradually increase to a fixed high value. Discharged air should continue to come from A/C outlets and should be warmer than the temperature in the work area. |
| OFF | 60° | Blower is off. Minor defroster and heater bleed when driving. |
| RR DEF | NONE | LED above button should light up. Heat should be applied to rear window. |
| OUTSIDE TEMP | NONE | LED to left of button should light up and out- side temperature displayed on control panel. |
ELECTRONIC CLIMATE CONTROL SYSTEM PERFORMANCE (Engine Warm & Idling)
Electronic controls drive a reversible DC motor, which positions the air-mix door in response to temperature changes and control settings. The sequence of events as the programmer moves from maximum A/C to maximum heat is as follows
- Possibility of recirculated air is terminated.
- Heater control valve opens.
- Blower speed gradually decreases from Hi to Low.
- Air-mix door starts to move and blends in hot air.
- Mode of air delivery changes from A/C to heater.
- Blower speed increases gradually from Low to Hi.
- Air-mix door reaches "Max Heat" position.
The sequence of events is reversed as the programmer moves from maximum heat to maximum A/C.
CONTROL PANEL
The climate control panel (CCP) is located in the instrument panel to the right of the steering column and consist of a key board and 3 digit vacuum fluorescent display. On FWD vehicles the CCP is in continuous 2-way communication with the Body Control Module (BCM) during system operation. The data is transferred back and forth over a single wire and accomplished by alternating the direction of digital "messages". The direction and timing of transferred "messages" is controlled through a circuit which is sent by the BCM.
There are Red and Blue push buttons that serve to increase or decrease the desired temperature in 1° steps between 65°F (18°C) and 85°F (29°C). A continuous touch will cause a change in the selected temperature at the rate of 2° per second until that mode button is released or the end of the scale is reached.
Settings of "60°F" and "90°F" are also available, represent- ing maximum cooling or maximum heating respectively. These 2 settings override any automatic temperature control inputs.
A White mode push button can be depressed to request a display of outside temperature. When the mode button is pushed a second time, the display will return to the desired "set" temperature.
Air Delivery Mode
In order to provide proper heating or cooling, the BCM will direct blend-air in one of several air delivery modes. While side window outlets receive air flow during all modes of operation, other outlets are directed by commanding the programmer to energize specific vacuum valves feeding the appropriate combination of mode door actuators. The BCM determines the proper air delivery mode based upon the current program number and control panel setting. The following delivery modes are possible
- Max A/C Mode A/C outlets with bleed to heater outlets. Air inlet door slowly opens if "AUTO" mode is selected, providing 80% recirculated air. In "ECON" mode this door will remain closed.
- A/C Mode A/C outlets with bleed to heater outlets. If previously in "AUTO- MAX A/C" mode, air inlet door will slowly close to provide 100% outside air.
- Intermediate Mode Defogger outlets with bleed to heater outlets. This mode is used to transition from A/C to heater mode or vice-versa. It won't occur if "HI FAN" is selected, in which case the system goes directly from A/C to heater or vice-versa.
- Heater Mode Air is directed to heater outlets with bleed-off to defogger outlets.
- Off Mode With the system at "OFF", the blower will remain off. However, any air which enters as the vehicle is moving will be directed the same as during the heater mode. The discharge air temperature will continue to be controlled by the air mix door.
- Front Defogger Mode Defogger outlets with bleed to heater outlets. This mode is not allowed to remain after the key is turned off. The system will switch to the "AUTO" selection if "Front Defog" was previously active. If the operator selects "Front Defog" while the outside temperature is below 25°F (-4°C), the BCM will limit the blower to 7 volts until the coolant has been above 110°F (43°C) for 3 minutes. This low blower voltage reduces the possibility of drawing snow through the air inlet.
PURGE MODES
There are 2 purge modes which occur under certain conditions when the A/C system is first turned on. Each of the purge modes is designed to reduce the possibility of windshield fogging.
Cold Purge
If the A/C system is turned on in "ECON" or "AUTO" when the coolant temperature is below 28°F (-2°C), cold purge is enabled. In cold purge the blower will be off and any air flow will be directed to the front defogger outlets to keep breath humidity off the windshield. Normal operation will resume several seconds after either of the following conditions exist
- Program number would result in A/C mode.
- Coolant temperature is above 110°F (43°C).
If neither of these conditions exist within 3 to 5 minutes (depending upon outside temperature) the BCM will automatically resume normal control.
Normal Purge
If the A/C system is turned on in "ECON" or "AUTO" the programmer number will result in heater or intermediate modes and the conditions for cold purge do not exist, normal purge is enabled. In normal purge the blower is turned off and any air flow is directed to the heater outlets with bleed to the A/C outlets, preventing any moist air from reaching the windshield. To further purge ducts of moist air, the BCM will operate the blower at low speed for several seconds just prior to resuming normal operation. Normal operation will be preceded by a low blower period after either of the following conditions exist
- Program number would result in A/C mode.
- Coolant temperature is above 110°F (43°C).
If neither of these conditions exist within 3 to 5 minutes (depending upon outside temperature) the BCM will automatically resume normal operation.
VACUUM FLUORESCENT DISPLAYS
The BCM responds to selected inputs and transmits the proper display temperature and mode indicator information back to the CCP over the data circuit. Based upon this information transfer, the CCP then illuminates its vacuum fluorescent display using 16 volts supplied by the BCM. Intensity of display is controlled by the BCM over the dimming control circuit. This circuit provides a variable instrument panel to allow consistent illumination between components.
SENSORS
The system has 2 disc-type thermistors, used to monitor in-vehicle and outside (ambient) temperatures. Information received from sensors is used to regulate in-vehicle temperatures. The in-vehicle sensor is mounted behind slots on the instrument panel top cover.
The sensor is an integral part of the aspirator. The thermostatic compressor cycling switch is also mounted on the evaporator case.
Coolant Temperature Sensor
On DFI equipped vehicles, the coolant temperature sensor is located in a coolant passage of the intake manifold. Its resistance is monitored by the ECM which in turn sends the coolant temperature value to the BCM over the "ECM to BCM" data circuit (459).
On diesel equipped vehicles, the coolant temperature sensor is also located in the intake coolant passage. However, its resistance is monitored directly by the BCM.
A/C High Side Temperature Sensor
The high side sensor is located in the high pressure refrigerant line between the condenser and orifice tube. By monitoring the refrigerant temperature, the BCM can determine the pressure based upon the pressure-temperature relationship of R-12 refrigerant.
A/C Low Side Temperature Sensor
The low side sensor is in the low pressure refrigerant line between the orifice tube and evaporator. The BCM monitors this sensor to determine the low side pressure by determining the pressure based upon the pressure-temperature relationship of R-12 refrigerant.
Outside Air Temperature Sensor
This thermistor-type sensor has no effect upon the in-vehicle temperature. It is used only to monitor outside air temperature, which is then displayed on the control panel. It is located in a small protective housing, just to the rear of the radiator grille.
ASPIRATOR
Aspirator provides an accurate measure of in-vehicle temperature. It is mounted on top of the A/C-heater assembly. Aspirator causes air to be drawn across the thermistor (sensor) by venturi action.
PROGRAMMER
The plastic programmer case contains temperature control components. It is mounted on the right end of the A/C-heater assembly. The amplifier and logic board are a combined unit.
Programmer accepts electrical signals from both the sensors and mode push buttons in the control head, and also provides output control signals. A reversible DC motor located inside programmer actuates a rotary shaft to drive the air-mix door link.
Signals from the circuit board actuate the vacuum solenoids within the programmer. These solenoids control the heater control valve, air door, mode door and defroster door.
AIR-MIX DOOR LINKAGE
Linkage consists of a plastic crank arm integral with the programmer output shaft, a serrated nylon retainer and a threaded rod. One end is connected to the air-mix door. The opposite end is retained by serrations in the nylon retainer.
HEATER CONTROL VALVE
Valve controls coolant flow through heater core. It is mounted on right rear of intake manifold. Valve is normally open, but is closed by vacuum when programmer is positioned at maximum A/C.
COMPRESSOR CUT-OFF SWITCHES
Vehicles equipped with diesel engines have a Wide Open Throttle (WOT) cut-off switch to disengage 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 (circuit 762).
Diesel vehicles also are equipped with a power steering pressure switch. This switch interrupts the compressor feed circuit (50) during heavy steering maneuvers. High power steering fluid pressure opens this normally closed switch.
On vehicles equipped with the DFI engine, there are no compressor cut-off switches. However, the ECM can request the BCM to momentarily turn the compressor off during heavy throttle operation with a signal sent over the "ECM to BCM" data circuit (459).
HEATER TURN-ON SWITCH
Switch is used on diesel engine models only. The bi-metallic snap-action switch remains open until coolant temperature reaches 95°F (35°C). Switch prevents heater blower operation while open. Switch is located near right rear corner of engine.
POWER MODULE
The transistorized power module is mounted on top of the evaporator-blower assembly. It receives signals from the ECC control head to cycle the A/C clutch.
It amplifies the signals to provide variable blower speeds. A heat sink, which protrudes into the air flow in the evaporator case, prevents module from overheating.
Scheme 2
- Remove glove box, set temperature control to "90°". Allow 1 or 2 minutes for programmer arm to travel to maximum heat position. Snap threaded arm from plastic retainer on programmer arm. (Scheme 2): Programmer and Air-Mix Door Linkage (Notice vacuum plug terminal numbers.)
- Check air mix door for free travel from full cold to full heat position, and pre-load in maximum heat position by pulling on threaded rod. Programmer output arm should align with arrow on programmer case.
- Snap threaded rod into plastic retainer on programmer arm. Set temperature to "60°", and check for air-mix door travel to maximum cool air position.
PROGRAMMER TEMPERATURE
- Set the control panel to "AUTO" at "75°". Connect voltmeter between pin "W" of programmer and ground. Record voltage. To increase temperature, increase programmer voltage by .2 volt for each 1° change desired.
- Using a small blade-type screwdriver, adjust potentiometer in programmer. If a cooler setting is desired, decrease voltage by .2 volt for each 1° change desired.
COMPRESSOR CUT-OFF SWITCH
Rotate switch lever until just short (approximately 4°) of full counterclockwise position. Insert a No. 43 drill (.089") through hole, holding lever in place. Rotate switch until lever contacts accelerator pedal lever. Tighten mounting nuts, then remove drill.
Compressor Cut-Off Switch Adjustment (Switch is used on diesel models only.). Scheme 3
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 either on or off. The status lights and modes they represent are as follows
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. This light should toggle between "rich" and "lean" (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 illuminates 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.
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%).
CADILLAC ECC FUNCTIONAL TEST CHART. Scheme 4
Note. Wait 1 or 2 minutes for system to change when changing modes and/or temperature.
Sensor Resistance Chart. Scheme 5
No Display On ECC Control Head. Scheme 6
TEST 2 - NO BLOWER OPERATION
| CAUTION | Tan (circuit 918) wire supplies blower ground connection. Avoid touching the terminal of tan wire while contacting chassis ground. Blower case is at a positive potential. |
No Blower Operation (1 Of 2). Scheme 7
No Blower Operation (2 Of 2). Scheme 8
Hi Blower Only. Scheme 9
Low Blower Only. Scheme 10
No Air From A/C Outlet In A/C Mode. Scheme 11
Compressor Not Engaged (1 Of 2). Scheme 12
Compressor Not Engaged (2 Of 2). Scheme 13
Compressor Engaged In Economy. Scheme 14
Insufficient Cooling. Scheme 15
No Recirculate. Scheme 16
Insufficient Heat At Temp. Setting Of 90 Degrees Fahrenheit. Scheme 17
Insufficient Heat At Temp Setting Of 85 Degrees Fahrenheit. Scheme 18
Front Defroster Inoperative. Scheme 19
Rear Defogger Inoperative. Scheme 20
Rear Defogger On Continuously. Scheme 21
Outside Temperature Always Displays Very Low. Scheme 22
Outside Temperature Always Displays Very High. Scheme 23
Sensor String Problem. Scheme 24
CONDENSER
- Discharge A/C system using approved refrigerant recovery/recycling equipment. Drain and remove radiator. Disconnect condenser inlet and outlet pipes and cap openings. Remove 2 mounting screws, brackets and insulators from top of condenser. Remove condenser from vehicle.
- To install, add one oz. of new refrigerant oil to new condenser. Reverse removal procedure. Use new "O" rings lubricated with refrigerant oil at connections. Evacuate and charge system.
| CAUTION | The power module heat sink may be very hot. Use care when handling to avoid burns. |
Disconnect battery ground cable. Disconnect 6-pin connector, Black ground wire and Tan blower wire. Remove attaching screws and power module. To install, reverse removal procedure.
EVAPORATOR CORE
- Discharge A/C system using approved refrigerant recovery/recycling equipment. Disconnect electrical connectors from blower motor, thermostatic switch, power module and radio lead-in connections. Position wiring harness to one side.
- Remove 2 screws from compressor cycling switch. Remove insulation, loosen 2 hose clamps and remove switch. Remove right windshield washer nozzle. Remove 3 screws to secondary inlet screen.
- Remove attaching screw on right side and partially remove rubber moulding above plenum chamber. Remove remaining screws and remove primary inlet screen. Remove blower motor. Disconnect evaporator to accumulator connection at top of accumulator.
- Remove screw and partially remove accumulator bracket. Remove all screws from top of evaporator case cover and remove cover. Disconnect condenser to evaporator connection. Remove evaporator core by lifting straight up and out.
- Remove old sealer from surface of module cover and replace with new sealer. Position evaporator core in module and connect lines using new "O" rings. Add 3 oz. new refrigerant oil to new evaporator. Reverse removal procedure to complete installation.
Heater and A/C Module. Scheme 25
HEATER CORE
- Disconnect electrical connections from power module, blower motor, thermostatic switch and radio lead-in. Position wiring harness out of way. Remove right windshield washer nozzle.
- Remove right secondary air inlet screen from plenum. Partially remove rubber moulding above plenum. Remove screws and remove primary inlet screen. Remove blower motor. Remove 2 screws securing thermostatic switch to module and carefully reposition switch off of module cover.
- Remove 16 fasteners and A/C module cover. Clamp heater hoses to prevent leakage, and disconnect hoses from core. Remove screw and retainer at top of core. With temperature door in maximum heat position, reach through housing and push the lower forward corner of core away from housing.
- Rotate core parallel to housing to snap core out of clamp. Remove core. Remove old sealer from module cover, and replacewith new sealer. Reverse removal procedure to complete installation.
EXPANSION (ORIFICE) TUBE
- Discharge system, using approved refrigerant recovery/recycling equipment, and disconnect evaporator inlet line. Remove as much impacted residue as possible and cap line and evaporator opening. Remove expansion tube and "O" ring from inlet tube with needle-nose pliers.
- Coat new "O" ring with refrigerant oil, and position on new tube. Insert short end of tube into inlet line. Push until tube reaches a firm stop to seat "O" ring. Add one oz. refrigerant oil to system. Connect evaporator line. Evacuate and charge system.
THERMOSTATIC SWITCH
- Remove electrical connector and mounting screws at top of evaporator housing. Remove insulation from connection at evaporator pipe and capillary line. Mark location of line on pipe. Loosen clamps securing line to pipe, and remove line.
- Clean evaporator pipe with solvent and position switch to module. Connect electrical connector. Position capillary line within 1/2" of original location.
- Tighten clamps so full width covers capillary line with both rows of line firmly against clean evaporator pipe. Pack installation with new insulation.
LOW PRESSURE SWITCH
- Discharge refrigerant system using approved refrigerant recovery/recycling equipment. Remove electrical connector at rear of compressor. Remove snap ring. Using pliers, pull switch from cavity.
- Lubricate cavity with clean refrigerant oil, and replace "O" ring. Install switch and snap ring. Pressurize compressor, and check to see that switch is actuated between 20-30 psi (1.4-2.1 kg/cm 2 ). Evacuate and charge system.
ACCUMULATOR
Note. See information under In-Line Filter-Drier.
- Discharge air conditioning system using approved refrigerant recovery/recycling equipment. Clean all dirt and grease from system connection points. Loosen evaporator-to-accumulator and accumulator-to-compressor fittings, and cap immediately to prevent moisture from entering system.
- Remove mounting clamp and accumulator. Drain and measure refrigerant oil in accumulator. Remove caps from evaporator fittings, and install accumulator. Use new "O" rings, lubricated with refrigerant oil. Add 2 oz. more oil to accumulator than drained during removal.
IN-LINE FILTER-DRIER
An in-line filter-drier may be installed as an alternative to replacing the accumulator. AC Delco supplies parts for installation in either nylon hose or aluminum pipe locations (depending upon underhood access and room availability).
IN-CAR SENSOR
- Remove screw on ends, front edge, and in defroster ducts on instrument panel top cover. Remove top cover. Remove screws and right instrument tell-tale panel.
- After disconnecting aspirator hose and electrical connector, remove screws and sensor from tell-tale panel. To install, reverse removal procedure. Sensor must be positioned with electrical connector toward right side of vehicle.
ECC CONTROL HEAD
Disconnect battery ground cable. Remove center trim plate from instrument panel. Remove 2 screws securing control head to instrument panel. Pull control head out. Disconnect electrical connector, and remove control head. To install, reverse removal procedure.
- Disconnect battery ground cable. Remove glove box liner and right side hush panel. On DFI models, remove ECM unit.
- Remove left hush panel from under dashboard (and C.B. transceiver, if equipped). Unsnap programmer arm from clip. Disconnect electrical and vacuum connectors. Remove 2 screws and programmer. To install, reverse removal procedure and adjust air-mix door.
OUTSIDE TEMPERATURE SENSOR
- Disconnect battery ground cable. Remove plastic retainers across top of radiator support, and remove front panel fillers.
- Disconnect 2-pin connector behind right headlight. Remove screw and temperature sensor. To install, reverse removal procedure.
