Rectifier to run accessory

A wiring diagram would be most helpful here so we could see what you actually have. Just guessing but the DC ground might could be a possible suspect?

You might have to tie the AC and DC grounds together.

I don't know if tying the AC and DC grounds together on this siding could contaminate (might not be the correct term) the ground on my entire layout, since the ground emanates from one of my phased transformers that control everything.

I agree that the DC ground is a suspect.

A sensible approach might simply be to use insulator pins in all 3 rails of the half tracks, and run new clean AC grounds to each end.

If it works better with DC, why not take the body off and add a bridge rectifier?  Track roller and groud to the inside terminals and your motor and lights to the outside terminals.  Check your polarity to see which way the fish are swimming and your are done.  Now you can take your fish anywhere.

Great idea. Thanks

On second thought, the ground will be a problem because the car frame grounds to the outside rails.

@cpasam posted:

On second thought, the ground will be a problem because the car frame grounds to the outside rails.

Not at all.  Disconnect the wires from from the track and connect them to the rectifier AC input.  Connect the wires for the motor and light bulb to the DC output.  Test it before you completely reassemble it to make sure the fish swim in the right direction.  If not, swap the leads.

Danr, that sounds like a winner! And as you say it will also allow the car to go anywhere on the layout as a bonus.

Why would using DC make this accessory less noisy?

The a c power changes polarity 60 times a second. This creates a buzz which will vibrate any part not securely fastened. It's the same as a buzzer door bell.

Be careful, running a AC coil on DC  can result in it drawing more current and running hotter. Watch that this modification does not damage the plastic on the car.

Thanks.