For 1990-2009 cars

Table 1: | Heater Mode
Table 2: | Vent Mode
Table 3: | Defrost Mode

#### Heater Mode

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 |

1. Adjust the heater controls to the heater mode, high blower speed.
2. Adjust the temperature control to hot.
3. With the ignition switch on, complete the following steps:

• | Inspect the airflow out of the heater outlet.

• | Inspect the outlet attachment.

Is the airflow high?

--

Go to Step 2

Go to Step 5

2 | Inspect the blower speeds for an airflow change. Is there an airflow change? | -- | Go to Step 3 | Go to Step 4
3 | Inspect the following components for proper operation:

• | The temperature valve

• | The actuator

Is the repair complete?

--

System OK

--

4 | Refer to Blower Motor Electrical Diagnosis. Is the repair complete? | -- | System OK | --
5 | Inspect the blower speeds for an airflow change. Is there an airflow change? | -- | Go to Step 6 | Go to Step 7
6 | Inspect the following components for proper operation:

• | The heater defrost valve

• | The vacuum actuator

Does the heater defrost valve and the vacuum actuator operate properly?

--

System OK

--

7 | Refer to HVAC Blower Controls System Check . Is the repair complete? | -- | System OK | --

#### Vent Mode

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Is the vent air too warm? | -- | Go to Step 2 | Go to Step 5
2 |

1. Turn the ignition switch ON.
2. Move the temperature control from FULL COLD to FULL HOT.
3. Listen for the temperature valve operation.

Is there a temperature valve operation?

--

Go to Step 3

Go to Step 4

3 |

1. Verify that the valve operates properly.
2. Inspect the system for the following conditions:

• | A binding actuator

• | A disconnected actuator

Is the inspection complete?

--

System OK

--

4 | Inspect the temperature valve actuator for proper electrical or cable operation. Refer to HVAC Air Delivery System Check . Is the repair complete? | -- | System OK | --
5 |

1. Perform a leak test on the system.
2. Inspect the heater outlet attachment.

Is there a system case leak?

--

Go to Step 6

--

6 |

1. Turn the ignition switch ON.
2. Move the temperature control from FULL COLD to FULL HOT.
3. Listen for the temperature valve operation.

Is there a temperature valve operation?

--

Go to Step 7

Go to Step 8

7 |

1. Verify that the valve operates properly.
2. Inspect the system for the following conditions:

• | A binding actuator

• | A disconnected actuator

Is the repair complete?

--

System OK

--

8 | Inspect the temperature valve actuator for proper electrical or cable operation. Refer to HVAC Air Delivery System Check Is the repair complete? | -- | System OK | --

#### Defrost Mode

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Inspect the system for an objectional defroster bleed. Does the system contain an objectional defroster bleed? | -- | Go to Step 2 | --
2 |

1. Inspect the following components for proper operation:

• | Heater and defrost valve

• | Vacuum actuator

2. Repair the components as needed.

Is the repair complete?

--

System OK

--