Gentlemen

I've two 5 year old S9351 servos. The first started making RC interferens two years ago so I changed it to my other S9351 and everything was fine. Now my secong servo started making interferens yesterday. Is there somthing wrong with the electronic in the servos or has it something to do with the play the the gears (there is a lot! )? With running engine and the front wheels off the ground, the wheels keep shanking like the servo can't find the center position (due to the play in the gears??). Can that make interferens?

Thanks gentlemen.

Probably the potentiometer inside has gone bad. After 5 years, thats to be expected.

It's not interference, the servo is trying to find center and because of the excessive play it can't. You see it more with the engine running because of the vibration. Time for a new set of gears.

Thanks guys.
Why did I get interference with the first servo? Also because of the gears?

The interference I wrote about, was unexpected throttle movements. When I changed the first servo, everything was fine again. Now it has started again.

No interference from the servo. The unexpected movements from the servo was due to defective thoothwheel inside the servo. At the same time the upper ball bearing in the throttle servo was full of dirt... Everything is fine now

Remove the horn and disconnect the linkage and see how it reacts. If its still the same then its not your linkage. If it is then well now you know the issue.

If it is a result of interference such as unwanted radio signals that would not be your servo but more likely the ESC being located too close the the receiver. Also some ESC's are more prone to generate noise than others. It must have a high enough switching rate to be above the frequency of your radio for best performance. Most good quality brushless esc's switch in the 15kHz range driving IGBT's.