I ordered a Mikado smoke unit from by friend in New York that is a Lionel parts supplier. He said a 3 week wait. After a couple days I called Lionel support and got the parts folks. Ordered the 6801295200 as shown on the parts diagram for the Lionchief Mikado 3158. Got in a week (yesterday). Didn't get a chance to install the unit until this morning. The little screws are a real problem getting them out and back in. Cause I had to use a super little screw driver to fit then my old fingers didn't have the power to back the screws out? So I did a pair of pliers holding the screw driver handle and finally got them lose. After removing the old unit and installing the new unit. Using the pliers and super small screwdriver I managed to get the job done.

I was not really comfortable the unit was the real problem and if this new unit didn't work I was going to buy another Mikado and call Lionel to fix 3158. I've seen allot of posts on the net with smoke unit failures and a new unit not fixing the problem. Seems like the board that controls when the fan motor should run was the problem. I even called Lionel to see if that board was available. I took the Mikado to the layout with out the casting on the frame so I could watch the fan. Low and behold the smoke unit worked great. So the fan motor was the problem in my case.

Big thanks to trainlarry for the information and link to the Mikado diagram. Id like to add that after the postman left the smoke unit in the mailbox the Fedx man shows up with my smoking MTH Pennsy F-3's.