Joenasnj Posted November 15, 2008 Share Posted November 15, 2008 i have a 1997 Subaru Legacy gt 2.5 sedan. I have a factory am/FM cass. with CD player. When the car is off the radio plays fine but when the car is running it get interference in FM mode. i thought the radio was bad so i changed it with a nother factory radio with the same problem. The radion was fine untill the past week. Any clues on the problem? thanks Joe Quote Link to comment Share on other sites More sharing options...
Durania Posted November 15, 2008 Share Posted November 15, 2008 I got radio interference once because of an alternator going out. Any other weird electrical anomalies? Quote Link to comment Share on other sites More sharing options...
nipper Posted November 15, 2008 Share Posted November 15, 2008 Bad Alt, chattering brushes in any electric motor in the car, a bad ground... nipper Quote Link to comment Share on other sites More sharing options...
Joenasnj Posted November 15, 2008 Author Share Posted November 15, 2008 Is there any way to be sure it is the alt? It is not making noise. thanks Joe Quote Link to comment Share on other sites More sharing options...
Joenasnj Posted November 15, 2008 Author Share Posted November 15, 2008 I checked the ground on the radio and it looks good will look at motor grounds. Quote Link to comment Share on other sites More sharing options...
johnceggleston Posted November 15, 2008 Share Posted November 15, 2008 Is there any way to be sure it is the alt? It is not making noise. thanks Joe remove the belt that drives the alternator. Quote Link to comment Share on other sites More sharing options...
Cougar Posted November 15, 2008 Share Posted November 15, 2008 You can check to see if the alternator is causing the trouble. While the car is not running you can pull the connector from the back side of the alternator, that will disable it. Then start it up and see what happens. After the check turn the car off and replace the connector. Alternator noise usually appears as a whinning sound in the audio and you can hear the RPM changes in the whine as the alternator changes speed. A bad antenna ground can cause this thing also. Quote Link to comment Share on other sites More sharing options...
Durania Posted November 15, 2008 Share Posted November 15, 2008 You don't need to fool around if you have an alternator going out. It is cheaper just to replace in your driveway than to get 50 miles away from home and it break down on you. Then you have to pay for the tow home, then do your alternator change. They are not hard and I can change them on a Subaru in 5 minutes. Quote Link to comment Share on other sites More sharing options...
Joenasnj Posted November 15, 2008 Author Share Posted November 15, 2008 Disconnected the alt. and that is not it. I'm going to check the ground on the antenna next. Quote Link to comment Share on other sites More sharing options...
nipper Posted November 15, 2008 Share Posted November 15, 2008 Does it change with engine rpm? Quote Link to comment Share on other sites More sharing options...
Joenasnj Posted November 16, 2008 Author Share Posted November 16, 2008 Does it change with engine rpm? Nope the sound is the same Quote Link to comment Share on other sites More sharing options...
Cougar Posted November 16, 2008 Share Posted November 16, 2008 The problem you are having doesn't appear to be typical. Usually it is the AM section that picks up noise, not the FM section. This is due to the way the modulation design works. I wonder if something is wrong inside the radio. I suggest you check and see if the noise goes away if you disconnect the antenna. If the noise is still present then it is most likely due to a problem inside the radio. There possibly could be noise feeding into it through the power lead I suppose but that is fairly remote I would say. Quote Link to comment Share on other sites More sharing options...
Joenasnj Posted February 9, 2009 Author Share Posted February 9, 2009 Does it change with engine rpm? On Am it does Fm not really some times not at all on fm. Quote Link to comment Share on other sites More sharing options...
mva5142 Posted February 9, 2009 Share Posted February 9, 2009 Spark plug wires? On old or damaged ones the current can cause interference if the insulation is bad. Also fits with the problem in that it only occurs when the engine is running. Good luck! Quote Link to comment Share on other sites More sharing options...
Gene J Posted February 10, 2009 Share Posted February 10, 2009 When the blower motor was dieing I had that issue. When the motor stopped running I replaced it and no more noise. Vary the speed on the blower and see it the noise changes. Quote Link to comment Share on other sites More sharing options...
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