smoke unit repairSmoke Unit - Repair Tips From David
Dewey Non-functioning smoke units are common.
Sometimes it's a simple
solution: Spray some WD-40 down the
stack, let it soak a bit, then 'turn up
the power' and see if it will start
smoking. This works if the problem is
gelled smoke fluid plugging the wick.
If this doesn't work, then it's
possible the heater unit is bad or the
wick has burned or broken or you may
only have a spider nest in the choo
choo unit. This requires dismantling the
loco, unsoldering the wires to the smoke
unit and measuring the resistance
(35-45 Ohms is within fac. specs.) If
this measures OK, try the spray method
again (Different people try different
fluids, you want a solvent that will
'cut' the smoke fluid, but won't start
a fire!) Also check to see if you can
blow air through the unit, sometimes
a spider will build a nest at the
Choo-Choo chamber opening. If none of
these work, then it's time to replace
the wick and heater, not an expensive
job, but one that requires care (and
in my situation, a pair of magnifiers!)
Note: While rebuilding
your smoke unit, it may be wise to clean the piston chamber and the piston.
A non-lubricating 'tuner cleaner' is useful, although other solvents
may be used. Follow the warnings on the product container!
The piston is self-lubricating, and addition of lubrication here may gum up
'da woiks' slowing down your locomotive! Hmm, OK, I'll try to give a description
of the operation, if I forget
anything someone else on the list will
point it out!
First, I like to remove all the solder
on the smoke unit wiring lugs
(this is true for both versions, BTW,
these instructions are for the SIB
versions) The heater wire will not solder,
it is just wrapped around the
lugs, and you will be able to see that
with the solder removed. Unwrap the
wires so they are free from the lugs,
you may now unscrew the top and lift
it off without disturbing the 'guts'.
There are two versions of this smoke
unit; by this point in time, either
can be found in any loco, if they have
ever been repaired or replaced. One
version has a separate bottom piece
(which usually leaks!) and the heater
is crosswise to the wheels (we'll call
this one A); the other version has a
cast bottom and the heater is parallel
with the wheels (we'll call this one
B). In either version, the heater is
insulated from the unit body with a
cardboard liner, which can be fragile!
Now that the top is off, inspect the
unit to see what happened. (If you had
no Ohm reading, obviously the wire is
broken somewhere, if you had a
reading, it's likely the wick will be
burnt). Also look for a little white
spider nest in the chamber between the
choo choo sound plate and the body.
If you had a good ohm reading, and the
wick isn't burnt, but you find the
nest, you can probably reassemble the
unit (well, ya gotta get rid of the
On the B version, all the guts will
just lift out, with care. On the A
type, it's best to remove the bottom
cover, pry out the wick, and cut it off
where it goes through the casting to
the top chamber, you can then carefully
lift out the heater from the top. On
the A type, the cardboard may stay
inside the body, that's fine, just leave
On both versions, blow through the piston
area to see if you get 'choo'
(you'll have to use your finger as a
'cover' for the little choo-choo
chamber) and that the small hole into
the chamber is clear. The cardboard on
the A type can sometimes shift and cover
the hole. Clean out the unit, you
may want to lightly sand the sealing
surface by placing it against a flat
surface with some fine (600 grit or
finer) sandpaper (Auto paint stores have
this to 2000 grit) but this is only
if you find it corroded.
The new wick/heater must be handled
carefully, you don't want any of the
heater wire crossing over itself, or
it will burn out quickly, if not
immediately! If you are working on a
type A unit, you will want the wick
ends to be stiff, some come with a 'glue'
already on them. This is so you
can start them through the tiny holes
in the bottom of the heater chamber!
If your wick isn't glued on the ends,
you can do this yourself with some
white glue (maybe gel type super glue,
I haven't tried it--but you don't
want the glue traveling up the wick!)
or, with patience, I have just twirled
the ends in my mouth like a painter
setting his brush--if you can get the
wick to come to a point so you can guide
it through the hole, that's all you
OK, A type repair: Wick is started through
both holes, carefully pull
both sides through until the heater
element is centered in the chamber area.
You don't want it against the bottom,
nor near the top, either spot will
cause failure; one burns the cardboard,
the other burns the lid! (That's
what makes that bulge in the cover seen
on some units.) Ideally it is just
in the air stream from the piston chamber.
Use a magnifier and check that no
wires are crossed! Cut off the glued
area of the ends and coil the wick in
the bottom chamber, it will fill it!
Here's where I 'cheat' a bit; I use a
very small amount of 'gasket in a can'
to seal the bottom chamber, as I
can't seem to get the factory gaskets
to not leak! A leaky unit will oil
your rails, but it's not the right kind
of oil!! See Roger Hinds
rail oil--disclaimer, I have no economic
interest in this 'plug'!. Back
to the repair:
B type: cut your old wick and remove
it from the cardboard chamber, thread
the new wick through the holes, and
as in the A type, center the wick so it
isn't too high or too low. Coil the
wick ends in the unit and check to see
that there is room for the cardboard
chamber to fit, and for air to pass
through the chamber, you may have to
cut off some of the wick to do this.
Again, look for crossed wires.
Both: Now you can fit the cover on,
I like to add some smoke fluid at this
time, to 'prime' the wick. Feed the
wires through the lug holes, check that
nothing changed while placing the cover
on (This is sort of like looking to
see if the refrigerator light goes out!).
Tighten the screws (you may use a
little gasket stuff here too, if you're
game). Check the coil Ohm reading,
if it's OK, then wrap the wires around
the lugs, resolder and test.
If you did everything right, you will
have a smoke unit that now will
chase everyone out of the room!
Trust me; the job becomes easier with
Dewey Watch the Railroad watch and repeat
after me, "The future is in S, the
future is in S, the future is in S,