Any RFI that sounds only when one window is going up or down will be easy to blame on the window motor. These noises are easy to associate with the source. Check the plugs, coil and any distributor for evidence of carbon tracking or arcing as well. Replace any suspect wires with factory or high-quality aftermarket wires. Resistance in the megohms or single digits may well be the source of not only your RFI, but a nagging misfire. Now get out your ohmmeter and measure the cables' resistance along their length-they should measure approximately 10,000 ohms per foot. Remove and replace the cables one at a time, clean them of grease and dirt with mild detergent, and check the connections to the ends. If your vehicle is more than a few years old, degraded cables may be the source of the problem. Virtually all cars today use resistor-type plug cables if they use spark plug wires at all. (Don't disconnect the alternator electrically-the back EMF may smoke the diodes.) If you think it's a fuel injector, try disconnecting it from the harness. This will be difficult in the case of the fuel pump or ignition, but you can pull the belt off the alternator. The top of the radio will point at the source like a gunsight.įind some way of disconnecting the source of the RFI and check to see if the noise ceases. Once you find the noise within a few feet, turn the radio 90° to minimize the noise. These cheapo radios use a ferrite-bar antenna that has good reception along its side, but poor reception along its length. Tune it to an empty channel around 1400 kHz, crank up the volume in your headset, and use the radio to sniff out the noise. Here's our favorite low-tech tool for hunting down and killing wild noises-a cheap AM radio. Other almost-constants are heater fans, wipers and electric radiator-cooling fans.Ĭandidates here include the alternator/voltage regulator, a faulty fuel injector and the ignition system. Then, when the computer senses that the engine isn't running, it will shut off the pump to prevent spilling fuel and draining the battery. Turn the key to the Run position without starting the car. The one motor that's guaranteed to be on whenever the car is running is the fuel pump's, and unfortunately it's usually buried inside the fuel tank. In other words, even though the noise comes from a radio speaker, it may be caused by any manner of device anywhere on your vehicle. Intermittent noises are easier to associate with a source, such as an electric seat adjuster or a power-window motor. An electric fan motor will also run at a constant speed-until you change the fan setting or turn it off. Constant-speed noises are usually caused by an electric motor-most likely the electric fuel pump found in the tank of most modern vehicles which runs at a constant speed anytime the engine is running. Likely culprits include the ignition, the alternator or even a fuel injector. This type of noise is caused by something that varies its speed with the engine. Our hapless father's problem was in the latter category-his noise varied up and down in pitch and volume as his engine sped up and slowed down. There are three classes of RF noise-constant, intermittent and engine-speed following. What you have here is radio frequency interference (RFI). But instead of the first inning, you hear what sounds like some awful guitar note-and it changes pitch as you speed up and slow down, turning to a maniacal rhythmic clicking as you wait for a traffic light to change. A lot of ballgames, actually, now that you don't have to listen to her headbanger music, with its shrieking vocals and droning guitars. You're looking forward to the chance to listen to the ballgame, having just dropped your purple-haired teenage daughter off at her first semester at college.
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