Interference noises due to power supply
NOTE:
Use this test routine for interference noises which originate from the vehicle electric.
RADIO SYSTEM DIAGNOSIS FOR INTERFERENCE NOISES DUE TO POWER SUPPLY
| Work instruction |
Yes |
No |
| 1 |
- Temporarily disconnect the connections B+ and ground on the radio.
- Connect B+ and ground temporarily via a separate lead.
- Connect the other end of this lead to the vehicle battery.
Interference noise still present? |
The interference noise is triggered via the radio. Step 2 |
- Reconnect the original cable connections to the radio.
- Temporarily disconnect the connections B+ and ground on the booster.
- Connect B+ and ground temporarily via a separate lead.
- Connect the other end of this lead to the vehicle battery.
If the noise is still present, the amplifier is the cause of the fault Step 2
Noise no longer present Step 3 |
| 2 |
Connect the other end of the improvised lead connection at the connection B+ to the fuse of the radio or the amplifier.
Interference noise still present? |
Lay B+ and the ground lead differently or insert a new lead and lay the new lead at a distance from all other current circuits.
Noise still present: Step 3
Noise no longer present: End |
Step 3 |
| 3 |
Check whether the noise occurs when a switch or an accessory component is switched on. |
Localise the cause for the interference noise in the retrofitted accessories and remedy. End |
The noise occurs when the engine is running. Step 4
The noise occurs with the ignition switched on and the engine at standstill Step 5 |
| 4 |
Briefly disconnect the connections on the alternator and start the engine. Noise still present? |
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| 5 |
- Find out which circuit is causing the interference noises by removing individual fuses, relays and switches.
- Insert all removed fuses, relays and switches again.
- Disconnect all components in turn which are connected to the affected circuit, until the interference noise has disappeared.
- Replace defective components.
Noise still present? |
Step 6 |
End |
| 6 |
- Lay all wiring harnesses from the defective component and the connecting leads with suitable clearance.
- Remove any audio cables which are causing the problem from the wiring harness.
Noise still present? |
Step 7 |
End |
| 7 |
- If the suspected components uses the same ground connection as a component of the audio system, establish a problem-free ground connection.
- If ground connections are running via the same wiring harness, separate them from each other.
- Wrap the B+ lead of the suspected component with a film or a metal tape and connect the lead to a ground connection.
- Check the ground connection with an ohmmeter at the negative terminal of the battery.
Noise still present? |
Step 8 |
End |
| 8 |
- Find the positive cable of the suspected component and cut the cable at the component side.
- Insert an interference filter between the connecting cables.
|
End |
End |