decided to replace the bachmann 4-6-0 smoke unit (burned out, or maybe not) with the sd45 aristo unit…direct power to the unit itself and full of fluid, 45 mins worth of smoke…installed in the 4-6-0, 2 maybe 4 minutes before i have to turn off and back on again…once or twice at VERY slow speeds, unit would function as intended…thought the circuit board (the one the on/off switch in the boiler front) was maybe overheating…bypassed the circuit board-on/off switch and same thing…2 maybe 4 minutes then nuttin…then i thought maybe unit overheating and shuting down due to a lack of air in the boiler…so i drilled a number of holes in the bottom hoping this would aleviate the condition…2 maybe 4 minutes later same thing, shut down…what am i over looking here??? when it smokes it smokes great…adds wonderful animation going around the tree…very old fashioned feeling…but i am tired of opening and closing this darn thing up…any suggestions???