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I am currently tackling my first PS1-PS3 upgrade on an MTH Allegheny. All functions are working properly EXCEPT the smoke unit. Fan is working, but I'm getting no smoke. So, I tested the resistence of the resistors and they were NOT at 8 ohms parallel so I ordered new resistors. Here is my question, I noticed when messing with the smoke unit that turning the new smoke switch that came with the kit to "off" did not turn off the fan of the smoke unit. Is this normal, is the switch bad?? Does the switch only turn on the power to the resistors??  It was a straight swap out with the old switch I believe. just curious as I wait for new resistors to be delivered.

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You don't need the switch suppled unless you're running conventical in DCS remote and DCS controls the smoke unit!!!!!!! you can take the switch out unless you're run conventional! the 4-pin connector on the s3/2 runs the fan and heating element. also, when you did the ps1 upgrade did you modify the smoke unit as the booklet states In the PS 3 kit? you have to cut traces which puts the 2 resisters in parallel, you'll solder the 2 resistors together at each end on the circuit by doing this you should have half of the value of one resistor because there in parallel! there is a picture in the book that shows you exactly how to solder and do this update! see pdf file page 28 n 29 for pictures depends which smoke unit your engine has!

PS you don't' need the volume control except for conventional running but you can actually jumper 2 wires together for full volume in conventual running and leave the pot out completely.

50as10709i.pdf (


Last edited by Alan Mancus

make sure that nothing touches the smoke unit's solder pads once installed. I had something short it out on mine.

There's a brass protrusion inside the shell that can touch. I forget what it was now. Something added on the outside and left sticking in too long. It only touched if the shell moved when the engine went around tight curves.

Thank you, I will check that as well!


You say they didn't measure 8 ohms, what did they measure.  Note they're not going to measure exactly 8 ohms, anything from around 7.5 to 9 ohms is fine.

They measured 4.7 ohms and one was coming unwound??? This was of course after soldering them together, cutting the trace and paralleling the resistors.

Last edited by LT1Poncho

Well, that's ugly, hopefully you didn't cook the smoke heater FET.  They are rated for two smoke units, so you're probably OK unless it was previously shorted or you had a frame short.

Well, I haven't had the body on since I started the PS3 upgrade on this engine. So possible it was shorted or bad prior to starting the upgrade. It was my father in laws engine originally so I don't know the history. I'm hoping a new set of resistors cures the issue. I have already replaced the smoke fan motor as it was non-functional. All other functions work.

Last edited by LT1Poncho

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