Lionel 2466W Tender Whistle Stuck

Last night I gave up two hours of sleep repairing a train whistle stuck in the on position.

The patient: Lionel tender associated with engine 675 (pictured below)

Problem: The whistle blows continuously each time AC current is applied to the track.

Taking off the cover: Taking off the cover was easy. Simply loosen the 4 screws in the 4 corners of the car and lift the cover. The two suspicious looking screws in the middle attach the whistle mechanism to the chassis. I learned this the hard way.

How Lionel whistle works: applying the whistle button on the transformer (or whistle controller) pushes a 3V DC current over the track. The 3V DC current activates the solenoid, thereby lifting this thin metal strip to make contact and start the whistle motor. When the whistle button is released, the metal piece is supposed to drop back (via gravity) so the connection is lost and the whistle motor stops.

My situation: After a quick inspection it was easy to see that the solenoid (part: Relay WSR-1) was not letting go of the thin metal plate at the bottom so the motor never disengaged. When I put it on the track and manually separated the contact by gently touching the metal piece, it fell as expected. When the whistle was applied, it started and stuck.

Transformer Check: My first suspicion was that there was some residual current left after the whistle button on the transformer was released. I checked this using a multi-meter. But, the transformer was performing exactly as expected.

Repairing the faulty relay: I could purchase a new digital controller, but for historical purposes, I tried a lo-tech solution first. It's possible that some oil or other material got into the mechanism so that the piece was sticking. I tried cleaning the contact points in the center of the relay. That didn't work.

Next, I cut a piece from a piece of standard copy paper and applied it as shown below - making sure not to interfere with the opening and closing mechanism. I inserted the strip of paper between the parts that were sticking, next I bent the paper and ran it up the side of the relay so I could apply a small piece of masking tape to the top. The paper allowed the magnet to lift the contact while separating the components so gravity would shut off the power when the whistle button was released. Working after several test runs.