Both Williams engines perform whistle/bell in neutral with 1VDC, but not in forward and reverse using ZW and K-line whistle controller because the Volt ohm meter registers .5 VDC!  This 1/2 VDC is adequate for Lionel and MTH , but not enough for the Williams.  How can I provide more VDC or adjust the engines to sound with less?

Thanks,

Cliff