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Generator Noise Diagnosis

Diagnostic Aids

Noise from a generator may be due to electrical or mechanical noise. Electrical noise (magnetic whine) usually varies with the electrical load placed on the alternator and is a normal operating characteristic of all alternators. When diagnosing a noisy generator, it is important to remember that loose or misaligned components around the generator may transmit the noise into the passenger compartment and that replacing the generator may not solve the problem.

Step

Action

Yes

No

1

Test the alternator for proper operation using the Alternator Tester. Refer to Charging System Test .

Is the alternator operating properly?

Go to Step 2

Go to Step 11

2
  1. Start the engine. Verify that the noise can be heard.
  2. Turn OFF the engine.
  3. Disconnect the connector from the alternator.
  4. Start the engine.
  5. Listen for the noise.

Has the noise stopped?

Go to Step 11

Go to Step 3

3
  1. Turn OFF the engine.
  2. Remove the drive belt.
  3. Spin the alternator pulley by hand.

Does the alternator shaft spin smoothly and without any roughness or grinding noise?

Go to Step 4

Go to Step 11

4

Inspect the alternator for a loose pulley and/or pulley nut.

Is the alternator pulley or pulley nut loose?

Go to Step 11

Go to Step 5

5
  1. Loosen all of the alternator mounting bolts.
  2. Tighten the alternator mounting bolts to specifications. Refer to Generator Replacement : LNQ  → LF1  → LE5 .
  3. Install the drive belt.
  4. Start the engine.

Has the noise decreased or stopped?

System OK

Go to Step 6

6

Inspect the alternator for the following conditions:

    • Stained or stretched electrical connections
    • Hoses or other vehicle equipment resting on the alternator, which may cause the noise to be transmitted into the passenger compartment

Are any electrical connections pulling on the alternator or are any hoses, etc. resting on the alternator?

Go to Step 7

Go to Step 8

7
  1. Reroute the electrical connections to relieve the tension.
  2. Reroute the hoses, etc. away from the alternator.
  3. Start the engine.

Has the noise decreased or stopped?

System OK

Go to Step 8

8

Inspect the drive belt for proper tension.

Is the drive belt loose?

Go to Step 9

Go to Step 10

9
  1. Replace the drive belt tensioner.
  2. Start the vehicle.

Has the noise decreased or stopped?

System OK

Go to Step 11

10

Compare the vehicle with a known good vehicle.

Do both vehicles make the same noise?

System OK

Go to Step 11

11

Important: If no definite alternator problems were found, be sure that all other possible sources of objectionable noise are eliminated before replacing the alternator. Replacing the alternator may not change the noise level if the noise is a normal characteristic of the alternator or the alternator mounting.

Replace the alternator. Refer to Generator Replacement : LNQ  → LF1  → LE5 .

Has the noise decreased or stopped?

Go to Step 12

-

12

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2

   


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