Static on AM band of car radio

With the engine running on my 97' Nissan Sentra I get static on the AM
radio band; FM is OK. When engine is not running, everything is fine.
Can anybody suggest a solution?

Larry

nccft wrote:
> With the engine running on my 97' Nissan Sentra I get static on the AM
> radio band; FM is OK. When engine is not running, everything is fine.
> Can anybody suggest a solution?
>
> Larry

Replace your spark plug wires.

nccft wrote:
> With the engine running on my 97' Nissan Sentra I get static on the AM
> radio band; FM is OK. When engine is not running, everything is fine.
> Can anybody suggest a solution?
>
> Larry

You need to do a bit of detective work first.

Pull the radio out so you can get to the antenna lead.
Now run the vehicle and listen for the static, while you hear it unplug
the antenna cable. If the static stops then it is coming in through the
antenna. If not it is coming through the power lead.

If you determine the static is coming through the antenna lead you will
need to do some work to eliminate it. Plug wires, cap/rotor are the
usual sources if they are old or damaged. However I have seen more than
one vehicle that had static from day one. With those the antenna lead is
usually run through the engine compartment near the ignition. You can
sometimes reroute that. Or the cable has a bad connection of the
shielding section to ground on one or both ends. Then the easiest way is
to actually shield the wire by wrapping it with some metal and ground
the tape well on both ends. You will want to check the existing cable
for a good ground on both ends as well.

If the static was still there then it is likely in the power feed wires.
There are a few ways to stop it. The easiest is to install filters in
the wires right there behind the radio. Filter both the power and the
ground leads for the switched and the constant power lead as well. The
filters are available in most electronics shops and at Best Buy type
stores as well.

The next way is a bit better and that is to get filters that attach to
the source of the static, usually the alternator(whine and static from
failing slip rings,diodes), ignition coil (popping static), fuel pump
(whirring noises). And there are a few others as well. By filtering at
the source you also keep the voltage spikes out of the ECM.

The last is to run new shielded wires up to a relay box that is
controlled by the factory wiring. It is about the best way BUT it is a
PIA and can get expensive.

--
Steve W.

nccft wrote:
> With the engine running on my 97' Nissan Sentra I get static on the AM
> radio band; FM is OK. When engine is not running, everything is fine.
> Can anybody suggest a solution?
>
> Larry

Probably the coax cable is partially unplugged somewhere.

"Steve W." > wrote in message
...
> nccft wrote:
>> With the engine running on my 97' Nissan Sentra I get static on the AM
>> radio band; FM is OK. When engine is not running, everything is fine.
>> Can anybody suggest a solution?
>>
>> Larry
>
> You need to do a bit of detective work first.
>
> Pull the radio out so you can get to the antenna lead.
> Now run the vehicle and listen for the static, while you hear it unplug
> the antenna cable. If the static stops then it is coming in through the
> antenna. If not it is coming through the power lead.
>
> If you determine the static is coming through the antenna lead you will
> need to do some work to eliminate it. Plug wires, cap/rotor are the
> usual sources if they are old or damaged. However I have seen more than
> one vehicle that had static from day one. With those the antenna lead is
> usually run through the engine compartment near the ignition. You can
> sometimes reroute that. Or the cable has a bad connection of the
> shielding section to ground on one or both ends. Then the easiest way is
> to actually shield the wire by wrapping it with some metal and ground
> the tape well on both ends. You will want to check the existing cable
> for a good ground on both ends as well.
>
> If the static was still there then it is likely in the power feed wires.
> There are a few ways to stop it. The easiest is to install filters in
> the wires right there behind the radio. Filter both the power and the
> ground leads for the switched and the constant power lead as well. The
> filters are available in most electronics shops and at Best Buy type
> stores as well.
>
> The next way is a bit better and that is to get filters that attach to
> the source of the static, usually the alternator(whine and static from
> failing slip rings,diodes), ignition coil (popping static), fuel pump
> (whirring noises). And there are a few others as well. By filtering at
> the source you also keep the voltage spikes out of the ECM.
>
> The last is to run new shielded wires up to a relay box that is
> controlled by the factory wiring. It is about the best way BUT it is a
> PIA and can get expensive.
>
> --
> Steve W.

It can also be the antenna itself. If the antenna is partially shorted
internally
(in the base) it will often receive FM very well, but not AM. In such a
case the RF from your engine can compete with the AM signals.

If it isnt the coax (which is more likely), you may want to check the
antenna
itself. At the radio/TV repair shop where I worked as a young man, we would
take a new antenna to the car, disconnect the coax from the base of the old
unit,
and try it by substitution.

nccft wrote:
> With the engine running on my 97' Nissan Sentra I get static on the AM
> radio band; FM is OK. When engine is not running, everything is fine.
> Can anybody suggest a solution?
>
> Larry


FM was invented just because of this problem.

Interference in the car usually comes from one or two sources- the
spark, or the alternator. Spark interference can come from bad spark
plug(s) or from using wrong type of plugs, or from bad wires or using
the wrong type of wires. Ignition intererence is a buzzing, popping, or
crackling sound.

Alternator noise can come from a bad diode in alternator, brushes on
their last legs (particulary if it is an old generator, not alternator),
or from inadequate filter in radio. Since this is rare, it is more
likely a filter component in radio has failed.

Alternator noise is a whining sound.

Spark plug wires used to be solid copper wires.Then, along came auto
radios and other electronic thingys for cars.And resistor spark plugs
and the types of spark plug wires that are used nowadays.
RFI, Radio Frequency Interference, something like that.
cuhulin

wrote:
> Spark plug wires used to be solid copper wires.Then, along came auto
> radios and other electronic thingys for cars.And resistor spark plugs
> and the types of spark plug wires that are used nowadays.
> RFI, Radio Frequency Interference, something like that.
> cuhulin
>
There are two kinds of plug wires made to suppress RFI. In one case a
resistor is built into the spark plug end of the wire. In the other, the
wire is made of a more resistive material so the resistance is
distributed all along the wire.

The distributed kind is better for RFI avoidance, but the wires do
degrade faster and need more frequent replacement.

One used to be able to buy RFI resistances that snapped to the end of
the wire, between the wire and the plug. These are rare, hard to get
now that wires are built with the wires built in.

Also, many plug types are available with resistors built in. So in some
cases you have choice of resistor or non-resistor version of the same plug.

nccft > wrote:
>With the engine running on my 97' Nissan Sentra I get static on the AM
>radio band; FM is OK. When engine is not running, everything is fine.
>Can anybody suggest a solution?

Find out what is causing the noise and fix it. The days when ignition noise
was the only AM radio issue are gone... now you have hash from the alternator,
lots of stuff radiating from the engine control system and the sensors, and
even the ABS stuff throwing out digital trash everywhere.

Check to make sure all shielding is still in place, then make sure all the
engine grounds are good and that includes the big ground strap to the block.
Then get a handheld AM radio and start moving it around to try and track down
whatever is radiating.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

nccft wrote:
> With the engine running on my 97' Nissan Sentra I get static on the AM
> radio band; FM is OK. When engine is not running, everything is fine.
> Can anybody suggest a solution?

The antenna cable shield may not be grounded adequately.

Determine whether the noise is from the alternator or the ignition.
There should be a filter capacitor between the alternator output and
ground, and Radio Shack and car stereo dealers sell hash filters that
are even better. An alternator with a bad diode will also generate
more noise than normal.

The quickest way I know of to see if the ignition system is the source
of noise is by wrapping the spark plug boots completely with foil and
grounding the foil to the head. That will block the arc at the
connection between the plug and wire, and some VWs had metal jacketed
plug wire boots for this purpose.

Ford recommended covering the tip of the distributor rotor with a very
thin coating of dielectric grease. Use only the very thick type sold
by parts stores and Radio Shack (their transistor heatsink grease).

Metal plug wires, even the magnetic (inductive) type, cause much more
ignition noise than resistive wires do.