RW transformer or whistling tender problem

[BJB]

Hello. I am having a problem with my wistling tender or my RW transformer. I don't know which. When I  pust the whistle controler on the transformer the whistle blows for about a second or so and then the relay in the tender drops out and it stops. I am assuming the recterfier in the transformer is good because the whistle strarts to blow. the diagram shows a resistor in the transformer which I thought if it was open would explain the problem but I cannot  find the resistor. Any Help??????????????Thanks. BJB