Thanks for all the feedback. I took everything apart, cleaned, rewired and tested individually. My test setup uses a 1034 with a 167 since the transformer doesn't have the whistle option. When I have the tender on the track by itself and hit the whistle button, it seems the whistle relay makes contact and then releases quickly. I can play around a little and get it to stay engaged long enough to get a whistle sound, but not a good solid whistle. I tried it with a KW transformer with similar but slightly better results.
I've repaired a couple other styles of tenders before and had better luck than this one. Thus, I'm struggling with where the problem is - transformer, 167, tender?
