MTH 20-2297-1 Smoke Unit Issue

It's just an air or fluid pocket. Blow some air down the stack.

A bubble will do that.

It can also happen if the wick is blocking the exhaust hole.

sometimes where you add the smoke fluid a bubble is created in the tube line  so it can't puff, you can blow down with a quick hard blow from your mouth and if when you blow down you can clear the bubble it will start and work !also could be your fan is not running or running slow do to fan is defective. I would try taking smoke unit apart first and make  sure wick is not burnt black or is blocking the path the air has to travel threw to make the smoke unit puff. if yu find the wick is burnt or very black change the wick and while your inside test the motor and make sure it will run on 2vdc us a battery if you don't have a power supply if it wont start on 2 volts the motor is defective!

Good luck

Alan

It's possible the impeller is loose on the shaft, or the fan chamber outlet is blocked and not letting the air through to exhaust the smoke.

I'll pop it open and have a look at it. 

sometimes where you add the smoke fluid a bubble is created in the tube line  so it can't puff, you can blow down with a quick hard blow from your mouth

A better way to clear the bubble is with putting a tooth pick down the stack to clear the bubble. I have seen too many engines covered with smoke fluid inside covering the boards and speakers from blowing hard down the stacks. It doesn't take much to clear the bubble. One diesel engine I fixed had the speaker in the fuel tank and it was saturated with smoke fluid and the sound quit. A new speaker fixed the sound.

The same can happen by over filling the smoke units and storing the engine on its side causing the smoke fluid to run out inside the engine. The above engine was never stored on its side, but it may have been filled too much and then with quick hard blows down the stack caused the fluid to go all over inside.

Good idea Joe, but many locomotives have crooked stacks where a toothpick won't fit.  Also, a lot of diesels have a non-removable grill over the exhaust, and you just have to add the fluid through the thin slits.  Way too thin for a toothpick.

Sometimes I use the empty dropper as a little bellows to blow a tiny puff of air down the stack, that usually works, and it's great for when a locomotive is out of the reach of bending over and blowing directly down the stack.

The empty little smoke fluid tubes that MTH includes with their engines work great as a bellows to push any bubbles from the smoke stack.

Another important thing I forgot to mention, is to turn off the smoke or shut off the engine when filling the engine with smoke fluid. It helps from having most of the problems mentioned above.

Just took the shell off. I haven't opened the smoke unit cover but I see this brown mark where the resistors are soldered, should I be concerned? 

Not really, the PCB will get brown over time, as long as it's not really charred, it'll still work fine.

Just opened it up. The batting I will replace (I added some smoke to it but no difference) the resistors are at 8.2 ohms each and the fan sounds like it's working. 

Since the resistors are in parallel, one can only hope they're really around 16 ohms.

Did you make SURE the impeller was not loose on the motor shaft?

Look in hole is it spinning? G

I have experienced the impeller loose on the shaft on a few steam locos. Seems the intermittent start/stop of the fan motor(due to corresponding chuff rate) over time loosens the impeller on the shaft. I have removed the impeller and used a small amount of super glue on the shaft of the fan motor. Seems to work for a while but be prepared to do it over again over time. Make sure the glue does not run down the motor shaft and get inside the motor. I have also created a flat spot on the shaft with wire cutters (being careful not to cut all the way through) and then applying the glue. Again, let me hear your ideas

The super-glue is a temporary fix, a new impeller fixes it for a much longer time.

Here's a good place to use your toothpick. With the engine shell off, turn on the smoke unit. Then ever so gently stick the toothpick into the hole of the fan impeller to see if it is turning while the fan motor is running. If it is not turning or if it stops when the toothpick touches it with the motor still running, then the impeller is loose.

Forest

A little update. I took the fan off, it spins (on dc but not in command or conventional) and it's kinda slow, I have another I can replace it with. Also I think I found why there was no air flow. A piece of the separator piece between the fan and heater section was blocking the air coming out, I removed it but no change. Should I replace the fan motor next? Btw, yes the heaters are at 8.1 ohms each, should I replace those too? 

Well, that will certainly stop the airflow!  If the fan motor runs and isn't really noisy, there's no reason to replace it.  I also don't see replacing the resistors, though they're not 8 ohms, they're 16 ohms.  Look again, they're wired in parallel, without removing them, you can't measure them individually!

• Is there now airflow out the stack?
• Is there now heat sensed?
• Do you have enough fluid in the smoke unit?  20 drops is NOT enough!

Replace fan motor.  Turning on DC power is not the same a PWM power to the fan at a lower voltage from board.  That is assuming that the board is providing correct power via the harness and connectors.  You can use a 6V bulb test the harness output to the motor.  G

GGG posted:

Replace fan motor.  Turning on DC power is not the same a PWM power to the fan at a lower voltage from board.  That is assuming that the board is providing correct power via the harness and connectors.  You can use a 6V bulb test the harness output to the motor.  G

Alright. I'll replace the fan and see if that makes a difference.