I don't know but I found this. Seems the whistle is triggered by a 5v boost of voltage. So if that is what your DC test is showing it should be good. Could just be a defective whistle in the tender.I recently purchased a SantaFlyer engine and tender... 6-30164-e and Lionel ZW transformer - Dc tests ok with meter when pushing whistle knob but no noise... Know it is a newer type tender and an old transformer... Is there another gizmo needed
Thank you for the info - much appreciated...this is what the innards look like...I don't know but I found this. Seems the whistle is triggered by a 5v boost of voltage. So if that is what your DC test is showing it should be good. Could just be a defective whistle in the tender.
https://ogrforum.ogaugerr.com/topic/lionel-sound-activation-button