Inspection Procedure 9

Inspection Procedure 9: Sound Mixed With Noise, Only At Night (AM).

The following can be considered as possible causes of noise appearing only at night.
1. It is significantly easier to receive long-distance signals at night. This means that even stations that are received without a problem during the day may experience problems at night. Remember that the weaker station is more susceptible to interference. The appearance of a beat sound may occur in the evening. A beat sound is created when two signals close in frequency interfere with each other. A common sign of this type of interference is a repetitious high-pitched sound that may over power the desired radio station. This sound is generated not only by sound signals but electrical waves as well.
2. The changing system may also be a source of noise. When diagnosing radio noise, do not over look the possibility of a problem with the vehicles generator.

DIAGNOSIS

STEP 1. Check the vehicles lighting system.

Q : Does the noise disappear when the vehicles headlights are turned "OFF"?

YES : Go to Step 2.

NO : Go to Step 3.

STEP 2. Check that the following actions disappear the noise.

Tune to a station with a stronger signal.

Q : Is there more noise than on radio in other vehicles?

YES : Consult the radio manufacturer's service center.

NO : Check that there is no noise.

STEP 3. Check that the noise fades away when the vehicle harness is moved away from the radio (if the harness is not in the proper position).

Q : Does the noise fade away when the vehicle harness is moved any from the radio (If the harness is not in the proper position)?

YES : Consult the radio manufacturer's service center.

NO : If there is more noise than other radios, consult the radio manufacturer's service center.