GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1998 🢒 Jimmy - 2WD 🢒 HVAC 🢒 HVAC Systems - Automatic 🢒 Air Delivery Improper
Table 1: Vacuum Actuator Table

Vacuum Actuator Table

Control Setting

Solenoid 1

Yellow

Vacuum Line

Function

HEATER/DEFROST

Solenoid 2

Brown

Vacuum Line

Function

A/C

Solenoid 3

Red

Vacuum Line

Function

HEATER

Solenoid 4

Blue

Vacuum Line

Function

DEFROST

Solenoid 5

Orange

Vacuum Line

Function

AIR/INLET

Fan-OFF (Mode-Auto)

ON

OFF

ON

OFF

OFF

Fan-Med. Speed (Mode-Panel)

OFF

ON

ON

OFF

OFF

Fan-Med. Speed (Mode-Panel/Floor))

OFF

OFF

ON

OFF

OFF

Fan-Med. Speed (Mode-Floor)

ON

OFF

ON

OFF

OFF

Fan-Med. Speed (Mode-Floor/Windshield)

ON

OFF

OFF

OFF

OFF

Fan-Med. Speed (Mode-Defrost)

ON

OFF

OFF

ON

OFF

Ensure the preliminary settings of the A/C are set on the dial temperature 28°C (82°F) and the ambient temperature 21°C (70°F).

Step

Action

Value(s)

Yes

No

1

Was the system check performed?

--

Go to Step 2

Go to Diagnostic System Check

2
  1. Install the scan tool.
  2. Turn the ignition switch to the RUN position.
  3. Inspect the heater and A/C control DTCs.

Are any DTCs present?

--

Go to Scan Tool Data Definitions

Go to Step 3

3
  1. Set the parking brake.
  2. Start the engine.
  3. Set the fan switch to medium speed.
  4. Cycle the HVAC system mode switch through all of the control settings listed in the Vacuum Actuator Table.
  5. Inspect for air flow from the selected mode switch position.
  6. Repeat this test with each mode switch position.

Does the air flow not change in any mode switch position?

--

Go to Step 4

Go to Step 8

4
  1. Rotate the mode select switch through each of the available positions.
  2. Place a hand under the IP on the heater and A/C solenoid assembly 3. Listen and feel for the solenoids energizing.

Are the solenoids operating correctly?

--

Go to Step 5

Go to Step 6

5

Install a vacuum gauge on the vacuum line (GRY) disconnected from the solenoid assembly.

Is vacuum present in the system?

--

Go to Step 12

Go to Step 7

6
  1. Inspect CKT 341 (BRN) for an open between the HVAC solenoid assembly and splice pack SP200.
  2. Repair as needed.

Is the repair complete?

--

Go to Diagnostic System Check

--

7

Inspect the vacuum hoses and repair any of the following conditions:

    • Loose
    • Broken
    • Pinched
    • Blocked

Is the repair complete?

--

Go to Diagnostic System Check

--

8
  1. Turn the ignition switch to the RUN position.
  2. Connect a scan tool.
  3. Use the special functions menu selection in order to turn on each of the 5 vacuum actuators.
  4. Place a hand under the IP on the heater and A/C solenoid assembly. Listen and feel for the solenoids energizing.
  5. Note which solenoid failed to operate.
  6. Disconnect the heater and A/C control.
  7. Use the schematic in order to inspect for the following conditions:
    8. • A faulty circuit
    • A short to battery
    • A short to ground

Do any of the conditions exist?

--

Go to Step 9

Go to Step 10

9

Repair a faulty circuit from step 8.

Is the repair complete?

--

Go to Diagnostic System Check

--

10
  1. Disconnect the heater and A/C control.
  2. Turn the ignition switch to the RUN position.
  3. Recall a faulty circuit noted in Step 8.
  4. Use a DMM in order to inspect for battery voltage on the heater and A/C control connector terminal with the faulty circuit.

Is the reading as specified?

9-16 V

Go to Step 11

Go to Step 12

11

Replace the heater and A/C control.

Is the repair complete?

--

Go to Diagnostic System Check

--

12

Replace the HVAC solenoid assembly.

Is the repair complete?

--

Go to Diagnostic System Check

--