For 1990-2009 cars

# A/C ELECTRONIC BCM & NON BCM SERVICE ECC

#### MODELS AFFECTED: 1980-1985 ELDORADOS AND SEVILLES 1981-1984 BROUGHAMS AND DEVILLES (RWD) 1985 FLEETWOOD BROUGHAMS (RWD) 1985 FWD FLEETWOODS AND DEVILLES 1982-1985 CIMARRONS THIS BULLETIN IS INTENDED TO CLARIFY SERVICEABILITY DIFFERENCES BETWEEN THE 1985 FWD FLEETWOOD AND DEVILLE BODY COMPUTER MODULE (BCM) CONTROLLED SYSTEM, THE RWD FLEETWOOD BROUGHAM, RWD DEVILLE, SEVILLE AND ELDORADO NON-BCM CONTROLLED ELECTRONIC CLIMATE CONTROL (ECC) SYSTEM AND THE CIMARRON AIR CONDITIONING (AC) SYSTEM. WHEN DIAGNOSING CADILLAC AIR CONDITIONING CONTROL SYSTEM CONDITIONS IN THE AREAS OF COMPRESSOR CYCLING, POWER MODULE, BLOWER MOTOR/FAN ASSEMBLY, PROGRAMMER AND ECC CONTROL/FUEL PANEL, IT IS IMPORTANT TO NOTE THE FOLLOWING DIFFERENCES. 1. COMPRESSOR CYCLING: THE 1985 FWD FLEETWOOD AND DEVILLE UTILIZES THE BCM TO MONITOR THE LOW SIDE REFRIGERANT TEMPERATURE THROUGH A THERMISTOR AND DOES NOT HAVE A COMPRESSOR CYCLING SWITCH. THE BCM THROUGH THE POWER MODULE CYCLES THE COMPRESSOR ON AND OFF TO MAINTAIN THE PROPER TEMPERATURE AT THE EVAPORATOR CORE, PROVIDED SUFFICIENT REFRIGERANT IS AVAILABLE. THE BCM ALSO MONITORS THE HIGH SIDE REFRIGERANT TEMPERATURE, THROUGH A THERMISTOR, TO DISENGAGE THE COMPRESSOR CLUTCH UNDER EXCESSIVE REFRIGERANT TEMPERATURE CONDITIONS. ALSO, THE HIGH SIDE REFRIGERANT TEMPERATURE IS USED TO CONTROL THE SPEED OF THE COOLING FANS. THE NON-BCM CONTROLLED ECC CADILLAC SYSTEM IS CYCLED BY THE COMPRESSOR CYCLING SWITCH THROUGH THE POWER MODULE BASED ON THE EVAPORATOR INLET PIPE TEMPERATURE. THE SYSTEM OPERATES DOWN TO FREEZING AMBIENTS, AS MEASURED BY AN OUTSIDE AIR TEMPERATURE SENSOR. ON ALL 1982-1984 2.0L AND 1985 2.8L CIMARRON AC SYSTEMS, THE COMPRESSOR IS CYCLED BASED ON THE ACTUAL LOW SIDE REFRIGERANT PRESSURE BY THE PRESSURE CYCLING SWITCH. THE 1985 2.0L CIMARRON, WITH THE V-5 AC COMPRESSOR, DOES NOT HAVE A COMPRESSOR CYCLING SWITCH. THE COMPRESSOR OPERATES CONTINUOUSLY WHENEVER THE AC MODE HAS BEEN SELECTED. ON NON-BCM CONTROLLED ECC SYSTEMS, ELECTRICAL CIRCUIT #977 INTERCONNECTS THE COMPRESSOR CYCLING SWITCH TO THE CONTROL HEAD, THE PROGRAMMER AND THE POWER MODULE. THE COMPRESSOR CYCLING SWITCH PROVIDES A GROUND PATH FROM THE CONTROL HEAD TO THE POWER MODULE. ON THE CIMARRON AC COMPRESSOR CYCLING SYSTEM, THE AC PRESSURE CYCLING SWITCH PROVIDES A VOLTAGE PATH TO THE COMPRESSOR CLUTCH. IF THE COMMON PROCEDURE OF APPLYING VOLTAGE TO THE PRESSURE CYCLING SWITCH CONNECTOR (TO ENABLE THE AC COMPRESSOR) IS USED ON A CADILLAC COMPRESSOR CYCLING SWITCH CONNECTOR, THE ECC CONTROL HEAD WILL BE DAMAGED. 2. POWER MODULE: THE 1985 FWD FLEETWOOD AND DEVILLE POWER MODULE SUPPLIES POWER TO THE B+ TERMINAL OF THE BLOWER MOTOR AND PROVIDES A GROUND TO THE AIR CONDITIONING COMPRESSOR CLUTCH. ON NON-BCM CONTROLLED ECC SYSTEMS, THE POWER MODULE PROVIDES A GROUND TO THE GROUND TERMINAL ON THE HOUSING OF THE BLOWER MOTOR AND SUPPLIES POWER TO THE AIR CONDITIONING COMPRESSOR CLUTCH. PLEASE NOTE THAT THESE ARE OPPOSITES AND MIXING SERVICE PROCEDURES COULD RESULT IN DAMAGE TO THE POWER MODULE. THE 1985 FWD FLEETWOOD AND DEVILLE POWER MODULE RECEIVES POWER THROUGH A RELAY. THE RELAY WAS ELIMINATED AT B.P. 218686 AND THE POWER FEED IS FROM THE BATTERY. THE RELAY WAS REINSTALLED AT B.P. 258901. ON NON-BCM CONTROLLED ECC SYSTEMS, THE POWER MODULE RECEIVES POWER FROM AN IGNITION SWITCH "ON" CONTROLLED, FUSED FEED. 3. BLOWER MOTOR AND FAN ASSEMBLY THE 1985 FWD FLEETWOOD AND DEVILLE BLOWER MOTOR AND FAN ASSEMBLY ROTATES IN A COUNTERCLOCKWISE DIRECTION. THE NON-BCM CONTROLLED ECC SYSTEM AND THE CIMARRON BLOWER MOTOR AND FAN ASSEMBLIES ROTATE IN A CLOCKWISE DIRECTION. THESE ASSEMBLIES ARE NOT INTERCHANGEABLE AND ARE BALANCED AS AN ASSEMBLY. REMOVAL AND REINSTALLATAION OF THE FAN ON THE MOTOR MAY AFFECT THE BALANCE OF THE ASSEMBLY. 4. PROGRAMMER: THE 1985 FWD FLEETWOOD AND DEVILLE HAVE SEPARATE CONTROLS FOR THE HEATER WATER VALVE AND THE AIR RECIRCULATION DOOR, AS DID THE 1980 ELDORADO AND SEVILLE. ALL OTHER CADILLAC NON-BCM CONTROLLED ECC SYSTEMS CONTROL THE HEATER WATER VALVE AND THE AIR RECIRCULATION DOOR SIMULTANEOUSLY. ON THE 1985 FWD FLEETWOOD AND DEVILLE, THE HEATER WATER VALVE CLOSES WHEN THE AIR-MIX DOOR REACHES THE MAXIMUM COLD POSITION, WHEREAS THE AIR RECIRCULATION DOOR DOES NOT OPEN UNTIL MAXIMUM AIR CONDITIONING IS REQUIRED. THE 1985 FWD FLEETWOOD AND DEVILLE MODELS DO NOT HAVE A PROGRAMMER ADJUSTMENT. THIS IS STILL POSSIBLE ON NON-BCM CONTROLLED ECC SYSTEMS TO ALLOW THE CONTROLLING TEMPERATURE TO BE MODIFIED TO A PARTICULAR COMFORT LEVEL. THE 1985 FWD FLEETWOOD AND DEVILLE PROGRAMMER IS NOT A REMANUFACTURABLE UNIT. THE NON-BCM CONTROLLED ECC PROGRAMMERS WILL CONTINUE TO BE REMANUFACTURED. THE PROGRAMMER MOTOR ON ALL ECC SYSTEMS CAN BE SERVICED SEPARATELY, TO CORRECT NOISE OR OTHER PROGRAMMER MOTOR RELATED CONDITIONS. 5. ECC CONTROL PANEL AND FUEL DATA PANEL: THE 1985 FWD FLEETWOOD AND DEVILLE ECC CONTROL AND FUEL DATA PANEL FACEPLATES (DIAL), PLASTIC HOUSING AND BULBS ARE SERVICEABLE. THE PLUG-IN BACKGROUND LIGHTING BULBS ARE P/N 7895189. THE COOLER/ WARMER/OUTSIDE TEMPERATURE ILLUMINATION BULB, P/N 16030172, HAS TWO LEADS THAT PLUG INTO SOCKETS. THESE MAY BE DIFFICULT TO REMOVE AND CARE IS TO BE EXERCISED AS TO NOT DAMAGE THE CIRCUIT BOARD. ON NON-BCM CONTROLLED ECC SYSTEMS, ONLY THE BACKGROUND LIGHTING BULBS, P/N 9417561, ARE SERVICEABLE.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.