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For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 1998 🢒 DeVille 🢒 HVAC 🢒 HVAC Systems - Automatic 🢒 Blower Motor Always On

Blower Motor Always On for Cadillac DeVille 1998

Circuit Description

The airflow is controlled by modulating the commanded blower voltage. The blower voltage varies the blower speed. The blower is a function of the program number when the blower is under automatic control. Adjustments are made based upon the following factors:

    • The vehicle speed
    • The coolant temperature
    • The sun load sensor

The following special cases may override the normal operation of the blower:

    • Limit snow ingestion
    • Purge the air ducts
    • Cool the instrument panel cluster
    • Enhance the heater warm-up performance

Test Description

If the blower is inoperative in the normal operating procedure, but operates properly in override, the IPC or data line between the IPC and the heater and A/C programmer is suspect.

Step

Action

Value(s)

Yes

No

1

Did you perform the Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check

2
  1. Turn the ignition to the OFF position.
  2. Inspect connector B of the blower motor.

Is battery voltage measured?

B+

Go to Step 3

Go to Step 4

3
  1. Disconnect the blower.
  2. Measure the resistance between connector C and battery voltage. Refer to Testing for Continuity in Wiring Systems.
  3. Measure the resistance between connector A and ground. Refer to Testing for Continuity in Wiring Systems.

Is the resistance greater than the specified value?

1.0 ohms

Go to Step 6

Go to Step 5

4
  1. Inspect CKT 754.
  2. If CKT 754 is OK, replace the heater and A/C programmer. Refer to Programmer Replacement .

Did you complete the repair?

--

Go to Step 8

--

5
  1. Inspect the fuse.
  2. Repair CKT 50 or CKT 542 as required. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 8

--

6
  1. Turn the key to the OFF position.
  2. Measure the resistance between connector B and ground. Refer to Testing for Continuity in Wiring Systems.

Is the resistance less than the specified value?

250K ohms

Go to Step 7

Go to Step 4

7

Replace the blower motor. Refer to Blower Motor and Fan Replacement .

Did you complete the repair?

--

Go to Step 8

--

8
  1. Use the Scan Tool in order to clear the DTCs.
  2. Verify proper operation of the system.

Did you clear the DTCs and verify the operation?

--

Go to Diagnostic System Check

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