Inspection Procedure 5: Mixed with Noise, Only at Night (AM).

The following factors can be considered as PROBABLE CAUSES of noise appearing at night.
1.Factors due to signal conditions: Due to the fact that long-distance signals are more easily received at night, even stations that are received without problem during the day may experience interference in a general worsening of reception conditions. The weaker a station is the more susceptible it is to interference, and a change to different station or the appearance of a beating sound* may occur.

note

Beat sound*: Two signals close in frequency interfere with each other, creating a repetitious high-pitched sound. This sound is generated not only by sound signals but electrical waves as well.

2.Factors due to vehicles noise: Alternator noise may be a cause.

DIAGNOSIS PROCEDURE

STEP 1. Check that the noise still obvious even when the lamps are off.

Q. Is the noise still obvious even when the lamps are off?

Go to Step 2.

Go to Step 3.

STEP 2. Check hat the following actions.

(1)Tune to a station with a stronger wave.

(2)Tune to a station with a stronger wave without completely extending the antenna (Mast antenna).

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

Consult the radio manufacturer’s service centre.

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)?

Consult the radio manufacturer’s service centre.

If there is more noise than other radios, consult the radio manufacturer’s service centre.