I have a Tweetsie 4-6-0 Big Hauler that I just installed a new chassis on. Everything works fine with the exception of the tender sounds. With the old chassis they work fine. With the new chassis I only get the "chuff" when I push the switch on the back of the locomotive down. Push switch down – chuff. Switch up – quiet. Down – chuff. I placed the old chassis on the track and reconnected the tender to make certain nothing had happened to the tender and it works as expected. Since I get the "chuff" when moving the button but not when the engine is in operation on the new chassis - Just wondering – could the polarity coming from the chassis to the tender possibly be reversed? There can't be much wrong. The chassis is brand new. The tender works great with the old chassis. I'm just looking for some input and hoping perhaps you guys have seen this before. Thanks in advance!!