Engine accelerates to top speed with smoke on

Answered in duplicate post.

When the smoke is on and engine running the smoke motor is working creating smoke and it is pumped out the stack in conjunction to the motor chugs. 

I have also previously reset the unit with the DCS and by manual operation as suggested by another tech.

When this started it worked fine one day and then next day when the smoke was activated it took off like a scared puppy and has been doing it since that day. I also checked for all the grounds having good connections.

Is there a way to check the smoke unit for proper electric  resistance and draw?

Will post the unit model numbers when I get home.

Thanks

The simple way it to unplug just the smoke fan connector and do a brief test.  If turning the smoke on without the fan connected doesn't run away, I'd replace the smoke fan motor, it's a $6 part.

Smoke fan runs on same source as tach reader.  If it gets noisy or has a high current draw it can effect the operations.  As stated replace smoke fan motor.  You may find it is soaked in smoke fluid which can cause the failure. G

I will surely look into that and try unplugging and then run it. If that is the cause do you have a web site those smoke motors can be purchased at? I do know it is a single unit and I could be wrong but I would imagine they all use the same style on a 2-8-4. Again if they do vary I will get the train numbers when I get home.

Ok here it is RailKing, 2001, Virginian, 2-8-4 Berk.

30-1177-1 w/ PS2

The MTH smoke motors are all the same for those, BE-0000041 is the part number.  Most MTH service guys should have them.

By the way we have a guy at our dept. His name is John and his nick name is Gunrunner.

Im trying to locate that part number but not finding it. On mth site they don't list it.

The most likely cause is noise from the smoke drive lines getting into the tach lines.  Sometimes, separating the smoke unit wires from the tach lines will do the trick.  Other times, if the ground is shared, the noise still gets through.  In the case of shared ground connections between the smoke fan and tach, you can move the tach to a different ground connection on the main connector on the board.  Call the service guys.  They have encountered this many times and should be able to help you.

It's more common in my experience that the smoke motor is drawing excessive current and causing the 5V supply to droop.  I have to say, given no connection issues, I've never seen or even heard someone suggest that separating the wires makes a difference.  Hard to believe there's enough induced noise to cause this solid a symptom.

MTH RD posted:

The most likely cause is noise from the smoke drive lines getting into the tach lines.  Sometimes, separating the smoke unit wires from the tach lines will do the trick.  Other times, if the ground is shared, the noise still gets through.  In the case of shared ground connections between the smoke fan and tach, you can move the tach to a different ground connection on the main connector on the board.  Call the service guys.  They have encountered this many times and should be able to help you.

This is hard to do unless the engine is a PS-2 5V board in the engine or a diesel.  Regardless, I have found that the noise comes from the fan motor going bad, and the easy solution is change the fan motor.  G

I will check the motor next couple days.

Ive inquired around and no one has these smoke fan motors. I can get them at mth but have to buy 5 for 30.00

Anyone here know who has these in supply  other wise I may have to buy the 5 which i don't need.

Thanks 

Ok testing the wires to the motor.... First off the motor does not turn at any point with the cuffing when smoke is activated.

Secind...   When I disconnect the power wires to the motor to test the current the train goes full speed whether the smoke is activated or not..

I'm guessing the smokmotor is bad and the system needs the electrical resistance from it to run properlly, that's a guess.

I bought 2 smoke motors that I should get Friday. After I install 1 I will update this post with the outcome.

The system doesn't need to see a smoke motor to run properly, I routinely run PS/2 and PS/3 on the bench with the smoke unit's totally disconnected.

That said any other ideas on the cause of the problem?

I'd look for wiring issues between the smoke unit and the board.  Since turning on smoke, even with the smoke unit disconnected causes the issue, that's where I'd start looking.

You may have an open wire in the tether.  There can be a weird affect with some 5V engines depending on how the tach is wired with smoke. G

Do you know where I can get the tether?

Engine 30-1177-1

It is part #30-1200124

Or

Also given another part #30-1000002

I think the first is the complete harness and the second is just the tether with wires. Eitger will do.

MTH has a universal harness you can purchase that requires soldering of the wires.  Can you post some pictures of what you have.

Frankly, this can get complicated and it may be better to let a tech test the board to ensure it is fine and work from there.  G

Thank you