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
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.
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.
Probably the coax cable is partially unplugged somewhere.
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.
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
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.
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
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.
Are you sure that heatsink grease is dielectric? Some of these heatsink greases are filled with salts like zinc oxide and may conduct electricity as well as heat. I wouldnt want this type of thing inside my radiator cap.
See do not spam me.
What kind of antenna? mounted on the driver's side pillar?
If so, remove one of the screws, get a "star" lockwasher, coat it in dielectric grease (Syl-Glide for brakes will work) and screw the screw in tight enough to break the paint. This will ground it to the body and get rid of static.
Note: when you remove the screw, look and see if there is metal under the screw. If not, remove the other one. When I did mine, I lifted the antenna mount, put a star washer under it, and one under the screw and never got static again.
Agreed. Two different things. The white stuff is zinc oxide with a little hydrocarbon emulsifier. Its a great heat conductor but is a semi-conductor so it is used in apps where there is no chance of conduction or where you want conduction. It hardens up with time and heat. The clear stuff is the non-conductive silicone grease.
It's not... it's intended to be thermally conductive and consequently it's not so good an electrical insulator. BUT a good electrical supply house will sell a silicone dielectric grease which is just plain unfilled silicone polymer.
I highly recommend packing every damn connector on the car with silicone dielectric grease. Twenty years later you (or whoever owns the car by then) will be very glad you did.
--scott
Right. It's the stuff AutoZone sells in little packets for $0.99 as "spark plug wire" grease. You can buy a whole can from CRC for $3.99, and unless you're like me, who uses it for everything, will last your lifetime, your kid's lifetie, and may run out with THEIR grandkids...
I use it for a lot of stuff, when I need a good, waterproof lubricant, freeing stuck bicycle chains, on the sliders for the doors, I even used it as a lubricant in the caliper slides on my Soob, because it does not attack the rubber boots, and resists moisture.
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