Rail King smoke unit fan

Virtually all the MTH steamers use the same AA-0000070 smoke unit, the fan, impeller, PCB, motor, and gasket are all individually available as is the complete smoke unit.  The wiring harness may be another matter, exactly what do you need there?

This is what I'm after. Thanks!!

You only need the motor (BE-0000041), not the diecast fan chamber.

John,

If you pull the impeller fan out of the chamber with needle nose pliers, you will see two tiny screws that attach the motor to the chamber. Easy to remove. For the harness just unsolder it and then re-solder it to the new motor.

When you install the new motor, make sure you align the polarity dot to the same colored wire as the old fan.  When installed, the fan should run clockwise, if it's backwards, the smoke output will be significantly reduced.

NJCJOE posted:

John,

If you pull the impeller fan out of the chamber with needle nose pliers, you will see two tiny screws that attach the motor to the chamber. Easy to remove. For the harness just unsolder it and then re-solder it to the new motor.

I pulled it apart, Joe--thanks!! The big challenge now is learning to solder something that small. Looks like I'll have to practice before tackling this one. 

John, you should have mentioned that when you were at the house.  You were standing next to my smoke unit parts box with about 50 motors in it.

Thanks Marty--no doubt I'll have another one that will need replacement down the road. I'm a bit surprised this one went bad as this loco has seen very little use--I bet it has less than 30 min. total run time. 

Little use is probably why it died.  If you pull it and oil the bearing you might hit it with 9V for a few seconds and get it back on line.  If the 9V does nothing, it is done for.

The new motors arrived from MTH. There are strange markings on them; on the top of each motor is a white dot and on one side of the housing is a red line. What do these mean?

Thanks

John

Well, usually the red line is the positive terminal if you want the motor to run clockwise.  It should generally line up with the white dot to indicate the positive terminal.  I just looked at a bunch of them in my parts box, they all agree.

Thanks John. That leads me to 2 more, and hopefully my last 2 questions : 

Does the yellow wire or the white wire go to the positive side of the motor?

Finally, I've seen info from MTH saying the fan is to run counter clockwise on most locos. How do I know which locos go in which direction?

I can't believe I'm actually attempting repairs like this, but thanks to everyone on this forum, so far so good. Many thanks. 

Hmm...  Yellow and white aren't the colors of the typical fan wiring for PS/2, not sure what you have.  Gray and green are the colors I see as a rule, gray is positive.

The fan should run clockwise, and I've never seen anything from MTH that contradicts that.  This is for the standard full-sized smoke unit that most locomotives use.   The idea is for the fan to blow air out of the offset air hole in the fan chamber.

Thanks for the photo and clarification, John--I really appreciate it. The loco I'm repairing (Blue Comet) is "ancient" as a lot of you guys would say--around 1998. I'm pretty sure this was the first scale Blue Comet MTH made, so I assume it's PS1. It has spent most of its life in the box, so no electronic updates have been done on it.   Before I break out the soldering iron, I'll make sure I have clockwise rotation and solder the wires accordingly.

Here's the diagram that indicates counterclockwise rotation is needed. Seeing how air is supposed to flow out of the housing, clockwise makes much more sense, but thought you'd want to see this anyway. 

Thanks again

John 

Actually, the curvature of the blades is supposed to have the convex part going forward, it's to reduce the fan noise.  I notice the older MTH and all the Lionel impellers had the convex side in the proper direction, now the new MTH impellers have them facing what I believe is the wrong way.  I think someone re-specified the fan design not understanding why the convex blades were used.

If you spin the fan CCW, the airflow will be reduced.

I'm also amused by the holes in the base of the impeller.  What's the purpose of reaching the screws through the impeller when you have to take it off anyway to remove the motor?  I'd love to know what that designer was smoking.

Follow what John told you.  Clockwise is what you want.  I see between 2-6 of these every week.  John, if the engine has not run much, do not count the fan motor as bad.   Spin the impeller by hand to change where the brushes sit on the commutator.  Hit the motor with 9 volts for a very short time in each direction.  Many motors have been replaced that did not need to be.

John. on the holes I have seen loose motors and you can do a short repair by hitting the screws through the holes.  I agree it is stupid.  I always do what you do and pull the impeller to see what is going on.

Marty, do you have any explanation as to why they changed the direction of the curvature of the fan blades?  I checked the new impellers I got and they go what I consider backwards. 

I have sought that info and nobody has given an answer.  One thing we both agree on is clockwise rotation.  I have seen late generation TMCC that turns the wrong way and fixed them.

I've seen a few TMCC engines with the fan running backwards.  Of course, if someone is repairing the Lionel models, the fact that Lionel frequently use black for positive probably throws them.

Always a smart thing to check rotation. 

Marty Fitzhenry posted:

Follow what John told you.  Clockwise is what you want.  I see between 2-6 of these every week.  John, if the engine has not run much, do not count the fan motor as bad.   Spin the impeller by hand to change where the brushes sit on the commutator.  Hit the motor with 9 volts for a very short time in each direction.  Many motors have been replaced that did not need to be.

John. on the holes I have seen loose motors and you can do a short repair by hitting the screws through the holes.  I agree it is stupid.  I always do what you do and pull the impeller to see what is going on.

Thanks John & Marty--I tried this and the motor didn't budge. At least the motors are cheap. I've now learned more about the anatomy of an MTH steamer than I ever thought I would. Some change from my tinplate!!

Your smoke unit is a PS-1 smoke unit not the generic PS-2 smoke unit.  Fan motor and many parts are the same, but your smoke unit has electronics on it to run the fan and heat the element.  Marty can hook you up, but there can be many reasons with a PS-1 unit why the fan doesn't run.  Bad rectifier, bad 5V Reg, bad trace, swollen gasket stopping impeller, bad motor, etc....  They are easy to repair if you have the parts.   G