For 1990-2009 cars

# SERVICE MANUAL UPDATE-SEC.8A CIRCUIT ID/COMPONENT LOCATION

#### SUBJECT: SERVICE MANUAL UPDATE - SECTION 8A ELECTRICAL DIAGNOSIS (CIRCUIT IDENTIFICATION/COMPONENT LOCATIONS)

#### VEHICLES AFFECTED: 1987-90 C, D, E, K

Please update your Service Information Manuals with the following information:

#### 1987 Eldorados and Sevilles

o On pages 8A-88-1, 8A-150-0, 2, 4, 6, 8, and 10: Circuit 724 is PURPLE/YELLOW, not a flex circuit.

o On pages 8A-150-0, 2, 4, 6, 8, and 10: Circuit 588 is BROWN, not a flex circuit.

o On pages 8A-150-4 and 8: Circuit 8 is GREY, not a flex circuit.

#### 1990 Eldorados and Sevilles:

o On pages 8A-88-1, 8A-150-0 and 2: Circuit 724 is PURPLE/YELLOW, not a flex circuit.

o On pages 8A-150-0 and 2: Circuit 588 is BROWN, not a flex circuit.

o On pages 8A-150-0 and 2: Circuit 8 is GREY, not a flex circuit.

#### 1988-1989 Broughams:

o On page 8A-110-10: Connector C399 is located in the trunk, below the package shelf, not under the rear seat.

#### 1990 DeVilles and Fleetwoods:

o On page 8A-44-4: The location of the Electronic Brake Control Module (EBCM) is behind the centre of the I/P, not below the ashtray, except on vehicles without SIR which have EBCMs located behind the left side of the instrument panel near the LH shroud.

o On page 8A-64-2 several component locations have changed. Please replace this page with the attached page 8A-64-2.

#### SYSTEM DIAGNOSIS

- Refer to Section 1C for diagnosis.

#### CIRCUIT OPERATION

The Compressor for the Air Conditioning System is belt-driven by the engine through the Compressor Clutch. The clutch allows the Compressor to be dis- engaged from the engine whenever air conditioning is not required.

The operation of the Compressor Clutch is controlled by the Electronic Control Module (ECM) by grounding the 366 circuit at connector C1, terminal C6. This energizes the A/C Compressor Compressor Control Relay and voltage is applied to the Compressor Clutch.

The Climate Control Panel (CCP) accepts input request from the driver via the front panel push buttons. The input signals determine the operating mode for the Climate Control System and are sent to the Body Computer Module (BCM) over a data line (Circuit 718). If the BCM senses that cooling is re- quired, it will signal the ECM to turn on the Compressor through a data line (Circuit 491).

The BCM cycles the Compressor on and off according to the temperature levels indicated by the A/C High Side and Low Side Temperature Inputs. Should the refrigerant level drop to a a point where further operation would damage the Compressor, the A/C Low Pressure Switch opens and the BCM signals the ECM to stop compressor operation.

The ECM also receives inputs which affect operation of the Compressor. The inputs are Throttle Position, Coolant Temperature, Vehicle Speed and Power Steering Pressure.

#### COMPONENT LOCATION

----------- A/C Compressor Control RH front of dash, Relay........................on bracket..........................201- 4-B

A/C Low Pressure Near RH fender, on Switch.......................A/C accumulator.....................201- 5-A

Body Computer RH side of I/P, Module (BCM).................behind glove box....................201-11-A

Compressor Clutch............RH front of engine, on A/C compressor...................201- 2-B

Compressor Clutch Lower front of engine, Diode........................in engine harness...................201- 2-B

Coolant Temperature Top center of engine, Sensor.......................behind distributor..................201- 4-C

Electronic Control Behind RH side of Module (ECM).................I/P, near shroud....................201-12-B

Fuse Block...................LH side of I/P, behind access door..................201- 5-B

Power Steering Lower rear of engine Pressure Switch..............compartment, on steering box........201- 1-E

Refrigerant High Engine compartments, Side Temperature Sensor......near RH strut tower.................201- 5-A

Refrigerant Low Side RH front of dash, Temperature Sensor...........on A/C line.........................201- 4-A

Relay Center.................Behind RH side of I/P, at RH shroud...................201-17-A

Throttle Position Top of engine, behind Sensor (TPS).................throttle body.......................201- 0-A

C108 (1 cavity)..............Lower LH side of engine compartment, in front of ELC Compressor Assembly.201- 2-A

C200 (60 cavities)...........Behind LH side of I/P, right of steering column............201-14-A

C210 (7 cavities.............Behind LH side of I/P, taped to composite harness..........201-16-A

C225 (56 cavities)...........Behind RH side of I/P...............201-12-B

G100.........................Engine Compartment,ahead of LH wheelhouse....................201- 2-A

G101.........................RH side of engine, on generator mounting bolt.............201- 0-A

S144.........................Engine harness, on RH side of rear valve cover............201- 0-C

S201.........................Composite harness, behind LH side of I/P......................201-16-A

S218.........................Composite harness, behind RH side of I/P......................201-17-A

S235.........................Composite harness, behind center of I/P.......................201- 8-B

S250.........................Composite harness, behind RH side of I/P......................201-12-B

S262.........................Composite harness, behind center of I/P.......................201- 8-B

S293.........................Engine harness, behind RH side of I/P.........................201-12-B

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.