GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 1980 🢒 Seville 🢒 Bulletins 🢒 INOPERATIVE POWER MODULE CHECK & REPLACEMENT PROCEDURE

INOPERATIVE POWER MODULE CHECK & REPLACEMENT PROCEDURE

MODELS AFFECTED: 1980-1987 ELDORADOS AND SEVILLES 1981-1987 RWD DE VILLES AND BROUGHAMS 1985-1987 DE VILLES AND FLEETWOODS

Some vehicles may experience one of the following conditions:

- Compressor clutch operates in off and/or econ setting - Compressor clutch does not operate - Compressor clutch cycles rapidly - Blower motor does not operate - Blower motor operates in off setting or with key off. NOTE: Low blower operation in the off setting is normal on 1980 Eldorados and Sevilles equipped with ECC - Power module fails repeatedly

The above conditions may be caused by an inoperative power module. Before replacing the power module for the conditions listed above, the blower motor and compressor clutch circuits should be checked using the procedures given below to determine if either may have contributed to the power module failure.

1980-85 Eldorados and Sevilles, 1981-87 RWD De Villes and Broughams

The following procedure should be used before replacing the power module to check the blower motor and compressor clutch circuits on the cars listed above.

To check the compressor clutch and circuit:

1. Disconnect the power module 6-way connector.

2. Jumper 12 volts to circuit 204 (pin C on 1980-81 E and K cars, pin A on all other cars) through a 5 amp in-line fuse. If the fuse does not blow within two minutes, the compressor clutch did not cause the power module failure (proceed to "Check the blower motor circuit").

3. If the 5 amp fuse blows, remove the compressor clutch coil connector and check the clutch diode using the diode check setting on a DVOM. if the diode checks bad, replace the diode.

4. Check voltage to ground and resistance to ground on circuit 204 with the power module and compressor clutch coil disconnected and the ignition in the run position using a DVOM. A voltage reading over .1 volt indicates there is a short to voltage on circuit 204, which should be repaired. If a short to ground is found on circuit 204, this should be repaired. If circuit 204 checks ok, replace the compressor clutch coil.

To check the blower motor circuit:

1. Disconnect the single wire connector (blower motor control circuit 918) from the power module. Select 60 DEG AUTO ECC setting.

2. Connect an ammeter with greater than 25 amp capacity between the single wire connector and ground. This will turn the blower on full and give a blower motor draw reading. if an ammeter with 25 amp capacity is unavailable, substitute a 20 amp in-line fuse for the ammeter and use heavy gage jumpers from circuit 918 to the in-line fuse and from the in-line fuse to ground.

3. If an ammeter is used: The amp draw after one minute (steady-state blower motor draw) should not exceed 20 amps. If blower motor draw exceeds this parameter, it should be replaced.

If an in-line fuse is used: The 20 amp fuse should not blow after five minutes of blower operation. If the fuse blows at any time during the five minute test period, replace the blower motor.

After completing all diagnosis, replace the power module.

1985-87 De Villes and Fleetwoods and 1986-87 Eldorados and Sevilles

The following procedures should be used before replacing the power module to check the blower motor and compressor clutch circuits on the cars listed above.

To check the compressor clutch and circuit:

1. Disconnect the power module 2-way connector.

2. Jumper circuit 204 (pin A of the power module 2-way connector) to ground through a 5 amp in-line fuse. If the fuse does not blow within two minutes, the compressor clutch did not cause the power module failure (proceed to "Check the blower motor circuit").

3. If the 5 amp fuse blows, remove the compressor clutch coil connector and check the clutch diode using the diode check setting on a DVOM. If the diode checks bad, replace the diode.

4. Check voltage to ground and resistance to ground on circuit 204 with the power module and compressor clutch coil disconnected and the ignition in the run position using a DVOM. A voltage reading over .1 volt indicates there is a short to voltage on circuit 204 which should be repaired. if a short to ground is found on circuit 204, this should be repaired. If circuit 204 checks ok, replace the compressor clutch coil.

To check the blower motor circuit:

1. Disconnect 4-way power module connector. Select 60 Degree AUTO ECC setting.

2. Connect an ammeter with greater than 25 amp capacity between the blower feed terminal pin A and a 12 volt source. This will turn the blower on full and give a blower motor draw reading. If an ammeter with 25 amp capacity is unavailable, substitute a 20 amp in-line for the ammeter and use heavy gage jumpers from circuit 65 to the in-line fuse and from the in-line fuse to a 12 volt source.

3. If an ammeter is used: The amp draw after one minute (steady-state blower motor draw) should not exceed 20 amps. If blower motor draw exceeds this parameter, it should be replaced.

If an in-line fuse is used: The 20 amp fuse should not blow after five minutes of blower operation. If the fuse blows at any time during the five minute test period, replace the blower motor.

After completing all diagnosis, replace the power module.

Note: When checking the blower motor draw if a 25 amp ammeter is not available, a 20 amp fuse may be substituted for the ammeter. The substitution of a 20 amp fuse is preferable to the use of an ammeter with a 100 amp or greater full scale reading. If a 20 amp fuse is substituted for an ammeter in the blower motor draw test, a blown fuse would indicate failure of the test.

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.