Schematic Reference: HVAC Schematics

DEFINITION: Auxiliary air temperature can not be adjusted from one or both auxiliary controls or auxiliary heating is insufficient.

1

Did you review the HVAC operation and perform the necessary inspections?

Go to Step 2

Go to Symptoms - HVAC Systems - Manual

Important: The auxiliary A/C system operates independently of the HVAC control assembly to provide heated airflow through the auxiliary system.

Does the HVAC control assembly operate and provide sufficient heating?

Go to Step 3

Go to Too Cold in Vehicle

1. Turn ON the ignition, with the engine OFF.
2. Place the Heat and/or A/C auxiliary blower motor switch in each speed position.

Does the auxiliary blower motor operate at all?

Go to Step 4

Go to Auxiliary Blower Motor Inoperative

Does the auxiliary blower motor operate correctly for each speed position?

Go to Step 5

Go to Auxiliary Blower Motor Malfunction

Is the vehicle equipped with an auxiliary A/C system?

Go to Step 6

Go to Step 8

1. Start engine.
2. Place the mode switch in the OFF, VENT, or FLOOR positions.

Does the A/C compressor operate?

Go to HVAC Compressor Clutch Does Not Disengage

Go to Step 7

Is the vehicle equipped with an auxiliary heating system?

Go to Step 8

System OK

Inspect the cooling system for the following:

Did you find and correct the condition?

Go to Step 18

Go to Step 9

1. Disconnect the vacuum hose from the auxiliary coolant bypass valve.
2. Start engine.
3. Place the auxiliary heater blower motor switch in the M1, M2 or M3 positions.

Is there engine vacuum present at the auxiliary coolant bypass valve vacuum hose?

Go to Heating Performance Diagnostic

Go to Step 10

Test the engine vacuum circuit of the auxiliary coolant bypass valve for a leak or blockage.

Did you find and correct the condition?

Go to Step 18

Go to Step 11

1. Turn OFF the ignition.
2. Disconnect the coolant bypass valve solenoid.
3. Connect a test lamp between the heater water control solenoid control circuit of the coolant bypass valve solenoid and a good ground.
4. Turn ON the ignition, with the engine OFF.
5. Place the auxiliary heater blower motor switch in the M1, M2 or M3 positions.

Does the test lamp illuminate?

Go to Step 12

Go to Step 13

Test the ground circuit of the coolant bypass valve solenoid for an open. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 18

Go to Step 14

Test the heater water control solenoid control circuit of the coolant bypass valve solenoid for a high resistance or an open. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 18

Go to Step 15

Inspect for poor connections at the harness connector of the coolant bypass valve solenoid. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 18

Go to Step 16

Inspect for poor connections at the harness connector of the auxiliary heater blower motor switch. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 18

Go to Step 17

Replace the auxiliary coolant bypass valve. Refer to Heater Water Bypass Valve Replacement .

Did you complete the replacement?

Go to Step 18

--

Replace the auxiliary heater blower motor switch. Refer to Heater Control Blower Switch Replacement .

Did you complete the replacement?

Go to Step 18

--

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2