GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2001 🢒 Jimmy - 4WD 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 Too Hot in Vehicle

Test Description

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

  1. The specified values are from the A/C System Performance Test.

    2.

  2. The voltage will vary between 0-12 volts during normal operation. The HVAC control module connector must be connected during this step.

Step

Action

Value(s)

Yes

No

Schematic Reference: HVAC Schematics

DEFINITION: The temperature can not be adjusted, or the cooling is insufficient during A/C operation.

1

Did you perform the HVAC Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check - HVAC Systems - Manual

2
  1. Turn ON the ignition, with the engine OFF.
  2. Place the mode switch in any position except OFF.
  3. Place the blower motor switch in each speed position.

Does the blower motor operate at all?

--

Go to Step 3

Go to Blower Motor Inoperative

3

Does the blower motor operate in any of the speed positions?

--

Go to Step 4

Go to Blower Motor Malfunction

4

Alternately place the Recirculation Door between MAX A/C and Vent.

Does the Recirculation Door operate move from the recirculation position to the outside air position?

--

Go to Step  5

Go to Air Delivery Improper

5

Does the Too Hot in Vehicle concern occur when A/C cooling is desired?

--

Go to Step 6

Go to Step 8

6

IMPORTANT:: For A/C compressor operation, ambient air temperature must be above 3°C (38°F).

  1. Start the engine.
  2. Place the blower motor switch in the maximum speed position.
  3. Place the mode switch in the MAX position.
  4. Place the air temperature switch in the coldest position.

Does the A/C compressor clutch engage?

--

Go to Step 7

Go to HVAC Compressor Clutch Does Not Engage

7

Perform the A/C system performance test. Refer to Air Conditioning (A/C) System Performance Test in Heating, Ventilation and Air Conditioning.

Did you find and correct the condition?

--

Go to Step 19

Go to Step  8

8
  1. Observe the drive shaft of the air temperature actuator.
  2. Place the air temperature switch from the coldest position to the warmest position.

Does the drive shaft of the air temperature actuator rotate?

--

Go to Step 9

Go to Step 10

9

Inspect the air temperature door and the air temperature actuator for the following conditions:

    • Misaligned air temperature actuator
    • Broken or binding linkages or air temperature door
    • Obstruction that prevents the air temperature door from operating within it's full range of motion
    • Missing seals to the air temperature door
    • Misaligned seals to the air temperature door

Did you find and correct the condition?

--

Go to Step 19

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

10

Test the ignition 3 voltage circuit of the air temperature actuator for an open or a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 19

Go to Step 11

11

Test the ground circuit of the air temperature actuator for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 19

Go to Step 12

12

Test the air temperature door control circuit of the air temperature actuator for an open, high resistance, short to ground, or short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 19

Go to Step 13

13

Important: Ensure that the HVAC control assembly connector is connected during this step to avoid misdiagnosis.

  1. Turn ON the ignition, with the engine OFF.
  2. Measure the voltage from the air temperature door control circuit of the air temperature actuator to a good ground.
  3. Place the air temperature switch from the coldest position to the warmest position.

Does the voltage measure within the specified values with a smooth transition between Cold and Hot?

12 V at Cold 0 V at Hot

Go to Step 14

Go to Step 16

14

Inspect for poor connections at the harness connector of the air temperature actuator. 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 19

Go to Step 15

15

Inspect the air temperature actuator, door and any attaching linkage for binding or a condition that prevents drive shaft rotation.

Did you find and correct the condition?

--

Go to Step 19

Go to Step  17

16

Inspect for poor connections at the harness connector of the HVAC control assembly. 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 19

Go to Step 18

17

Replace the air temperature actuator. Refer to Air Temperature Actuator Replacement .

Did you complete the replacement?

--

Go to Step 19

--

18

Replace the HVAC control assembly. Refer to Heater and Air Conditioning Control Replacement .

Did you complete the replacement?

--

Go to Step 19

--

19

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2