Is this normal ZW whistle operation?

[Dougaz]

I'm restoring a ZW model R. In testing the two whistle control switches with both a whistle ltender and diesel with a horn both whistle switches on both sides of the ZW when moved about 2/3 of their full travel produce a consistent whistle or horn sound. But if the switch is pressed all the way to the end of travel the whistle or horn drops out and sometimes the engine e-unit cycles. I can get pretty good at getting the whistle or horn to work so long as I don't push the switch too far. Is this normal or should they sound and hold if I push the switches quickly all the way?

[ADCX Rob]

Completely normal.

If you study the schematics and the Lionel whistle operation theory, you will see that there must be a load on the circuit beyond that of just a standing/idle piece of equipment to draw enough current through the rectifier to reach the "hold" threshold voltage of the DC component imposed on the AC.

[rrlineman]

Your contacts are dirty, clean with 2-26 electrical cleaner. And most likely after more then 50 yrs the whistle diodes are breaking down and need to be replaced. You can use a 6-10A stud rectifier with a 50PIV volt rating as a replacement. Been fixing whistles this way for over 10 yrs now.