Before you replace or send in your servo for service, test it to make sure that it is not the receiver that is causing the servo to fail. A damaged receiver could also cause one or all of the servos to fail, so it is important that you test the servo to narrow down the problem. Simply unplug the servo that is not working from the receiver and plug it into a different channel.
For instance, if the steering servo is not operating, unplug the connector that is installed into channel 1 on the receiver and plug it into the channel 2. Of course you'll need to temporarily unplug the throttle/brake servo in order to perform the test. Operate the throttle trigger to test the steering servo. If the servo still does not work, then it's time to replace or service the servo. If the servo operates normally when installed on a different channel, then it's the receiver that is causing the servo failure.
Don't want to fix it yourself? Click here for instructions on how to obtain service.