Blower Motor Does Not Operate Properly Front
Circuit Description
The airflow is controlled by modulating the commanded blower voltage that varies the blower speed. Under automatic control, the blower adjustments are made based upon the following factors:
| • | The vehicle speed |
| • | The coolant temperature |
| • | The sun load sensor |
Special cases exist that may override the normal operation of the blower in order to limit the following conditions:
| • | Snow ingestion |
| • | Purging the air ducts |
| • | Cooling the instrument panel cluster |
| • | Enhancing the heater warm-up performance. |
Diagnostic Aids
If the blower is inoperative in the normal operating procedure, but operates properly in the override, the IPC or the data line between the IPC and the heater and A/C programmer are suspect.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the HVAC diagnostic system check? | -- | Go to Step 2 | Go to Diagnostic System Check |
2 |
Did you complete the procedure? | -- | Go to Step 3 | -- |
3 | Is the blower operation non-existent or intermittent? | -- | Go to Step 6 | Go to Step 4 |
4 | Does the blower speed consistently decrease at a gradual rate from 99 to approximately 30, and then stop? | -- | Go to Step 7 | Go to Step 5 |
5 | Is the blower speed consistent, then OFF? | -- | Go to Step 8 | -- |
6 |
Does the commanded value equal the actual value? | -- | Go to Step 10 | Go to Step 9 |
7 | The blower is operating properly. Inspect for improper temperature control. Did you inspect for improper temperature control? | -- | Go to Step 18 | -- |
8 |
Is the voltage greater than the specified value? | 9 V | Go to Step 17 | Go to Step 13 |
9 |
Is the blower speed (%) within the specified value? | 40-100% | Go to Step 10 | Go to Step 11 |
10 | Inspect the voltage at the blower motor connector B. Is the voltage greater than the specified value? | 4 V | Go to Step 12 | Go to Step 13 |
11 | Replace the heater and A/C programmer. Refer to Programmer Replacement Is the repair complete? | -- | Go to Step 18 | -- |
12 |
Is the resistance greater than the specified value? | 1.0 ohms | Go to Step 14 | Go to Step 15 |
13 |
Is the repair complete? | -- | Go to Step 18 | -- |
14 |
Is the repair complete? | -- | Go to Step 18 | -- |
15 |
Is the resistance less than the specified value? | 250 Kohms | Go to Step 13 | Go to Step 16 |
16 | Replace the blower motor assembly. Refer to Blower Motor and Fan Replacement Is the repair complete? | -- | Go to Step 18 | -- |
17 | Set the blower speed to HI. Does the voltage change to less than the specified value? | 4 V | Go to Step 16 | Go to Step 13 |
18 | Using the Scan Tool clear the DTCs and verify the operation. Did you clear the DTCs and verify the operation? | -- | Go to Diagnostic System Check | -- |
Blower Motor Does Not Operate Properly Rear
Circuit Description
Power is available from the CONSOLE fuse through the switch to the blower motor and ground. A series of three resistors contained in a module vary the circuit amperage that controls the blower speed. The heater and A/C programmer receives a feedback voltage signal, but this has no effect on the rear blower operation.
Test Description
The numbers below refer to step numbers on the diagnostic table.
-
If CKT 52, CKT 850, and the HI position have continuity, then the measurement will be nearly zero. As slower speeds are selected, the ground path of the blower motor passes through more resistors in the module. More resistors in the ground path increases the voltage at S345. Turn off the rear blower switch in order to measure the voltage.
-
If a resistor in the module is open, all of the cavities beyond that resistor will also be open. If cavity E operates the blower, then the fault is in the switch or in the wiring to the switch.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Functional Check? | -- | Go to Step 2 | Go to Functional Check |
2 |
Does the rear blower motor operate in any setting? | -- | Go to Step 6 | Go to Step 3 |
3 |
Refer to Measuring Voltage in Wiring Systems. Does the voltage measure near the specified value? | 10-15 V | Go to Step 4 | Go to Step 7 |
4 |
Does the resistance measure within the specified range? | 0-1 ohms | Go to Step 5 | Go to Step 12 |
5 | Connect a non-powered test light across the harness terminals A and B. Refer to Troubleshooting with a Test Lamp in Wiring Systems. Did the test light illuminate? | -- | Go to Step 10 | Go to Step 13 |
6 |
Refer to Using Fused Jumper Wires in Wiring Systems. Does the blower motor run at the correct speeds? | -- | Go Step 8 | Go to Step 9 |
7 |
Did you find and correct the condition? | 0-6 amperes | Go to Functional Check | Go to Step 11 |
8 | Inspect for poor connections/terminal tension at the rear blower motor switch connector. Refer to Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Functional Check | Go to Step 16 |
9 |
Refer to Wiring Repairs in Wiring Systems. Did you find and repair the condition? | -- | Go to Functional Check | Go to Step 15 |
10 | Inspect for poor connections/terminal tension at the rear blower switch connector. Refer to Connector Repairs in Wiring Systems. Did you find and correct condition? | -- | Go to Functional Check | Go to Step 14 |
11 |
Refer to Wiring Repairs in Wiring Systems. Did you find and repair the condition? | -- | Go to Functional Check | -- |
12 |
Refer to Wiring Repairs in Wiring Systems. Did you find and repair the condition? | -- | Go to Functional Check | -- |
13 |
Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Functional Check | -- |
14 | With the ignition off, use a non-powered test light in order to test CKT 52 for a short to voltage. Refer to Wiring Repairs in Wiring Systems. Did you find and repair the condition? | -- | Go to Functional Check | Go to Step 16 |
15 | Replace the resistor module. Did you complete the repair? | -- | Go to Functional Check | -- |
16 | Replace the rear blower motor switch. Did you complete the repair? | -- | Go to Functional Check | -- |
