Test Description

WARNING: This page is about a different car, the 2004 Pontiac Grand Prix. However, it is still accessible from the selected car via links, so may be relevant.

The number(s) below refer to the step number(s) on the diagnostic table.

2: This step will determine if one or more blower speeds are inoperative.
3: This step determines if the HVAC control module and blower motor control processor are attempting to control the blower motor speed.
5: The measured voltage on the blower motor speed control circuit should steadily decrease from 4.60 V to 1.1 V as the blower motor speed is adjusted from the minimum speed position to the maximum speed position.

Blower Motor Malfunction

Step	Action	Value(s)	Yes	No
Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views DEFINITION: The blower motor operates in at least one, but not all, speed positions.
1	Did you perform the HVAC Diagnostic System Check?	-	Go to Step 2	Go to Diagnostic System Check - HVAC Systems - Manual
2	Turn ON the ignition, with the engine OFF. Place the blower motor switch in each speed position. Does the blower motor operate at the desired speed(s)?	-	Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems	Go to Step 3
3	Turn OFF the ignition. Disconnect the blower motor connector. Turn ON the ignition, with the engine OFF. Connect a test lamp between the blower motor supply voltage circuit and the blower motor control circuit. Place the blower motor switch from the minimum speed position to the maximum speed position. Does the test lamp illuminate and increase intensity?	-	Go to Step 7	Go to Step 4
4	Test the battery positive voltage circuit and ground circuit of the blower motor control processor for high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition?	-	Go to Step 13	Go to Step 5
5	IMPORTANT: Ensure that the blower motor control processor and HVAC control module connectors are connected during this step in order to avoid misdiagnosis. Backprobe and measure the voltage from the blower motor speed control circuit at the HVAC control module to a good ground. Gradually adjust the blower motor switch from the minimum speed position to the maximum speed position. Does the measured voltage continuously decrease between the specified values?	4.7-1.0 V	Go to Step 8	Go to Step 6
6	Turn OFF the ignition. Disconnect the HVAC control module. Turn ON the ignition, with the engine OFF. Measure the voltage from the blower motor speed control circuit of the HVAC control module to a good ground. Does the voltage measure near the specified value?	5.0 V	Go to Step 8	Go to Step 9
7	Inspect for poor connections at the harness connector of the blower motor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?	-	Go to Step 13	Go to Step 10
8	Inspect for poor connections at the harness connector of the blower motor control processor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?	-	Go to Step 13	Go to Step 11
9	Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?	-	Go to Step 13	Go to Step 12
10	Replace the blower motor. Refer to Blower Motor Replacement in Heating, Ventilation and Air Conditioning. Did you complete the replacement?	-	Go to Step 13	-
11	Replace the blower motor control processor. Refer to Blower Motor Replacement . Did you complete the replacement?	-	Go to Step 13	-
12	Replace the HVAC control module. Refer to HVAC Control Assembly Replacement . Did you complete the replacement?	-	Go to Step 13	-
13	Operate the system in order to verify the repair. Did you correct the condition?	-	System OK	Go to Step 2