REPAIRS
Changing Thumbwheel Switch Or Motor
1. Read all instructions below before starting! Turn timer to “off.”
2. TURN OFF POWER SUPPLY TO KILN AND UNPLUG FROM THE WALL OUTLET.
Grasp molded plug cap to unplug do not pull out by cable.
[Insert FIGURE 11-1 THUMBWHEEL ASSEMBLY]
3. Remove control panel from body of the kiln by removing the 6 sheet metal screws along the
edge of the panel. The panel is easier to work on if you place a small box (8” high) under it
for support before unscrewing the panel. Remove cone supports from Kiln Sitter
® and store
in a safe place. Pull the panel straight out from the kiln being careful not to damage the kiln
lining with the tube assembly.
4. Notice the motor, thumbwheel, and switch that are mounted on a bracket (a) that may be
removed as one unit. Remove two 6/32” nuts (b) and washers from the bracket and pull the
entire thumbwheel assembly away from the panel.
NOTE: Rotate the thumbwheel so the set screws are visible (c). There are two holes in the
thumbwheel, one above and one below. There are two set screws in each hole, one on top of the
other (piggyback). The first set screw must be taken completely out and second one loosened to
change the defective part. You will need a 5/64” allen wrench to loosen the set screws.
Installation
After completing the thumbwheel assembly removal above, remove the two mounting screws (D)
from the bracket and lift the motor up and away. Install the new motor into thumbwheel making
sure the flat part of the shaft is in line with the set screw hole. Tighten all screws.
220 volt kilns – Use part -620 220vac 60 cycle 3W 2/5 RPH l146RK-1WR-6.
NOTE: This motor looks very similar to the Dawson Kiln Sitter
®/Timer motor, but is not the
same speed (RPH) and will not work satisfactorily. Make sure you have the correct motor before
changing the motor. Look at the engraved information on the side of the motor to check against
specifications shown above. Reconnect wires from the new motor to the speed control, relay, etc.
Thumbwheel Switch Replacement
Loosen set screws under thumbwheel. Remove (E) 5/8” nut with a pair of needle nose pliers.
Drop old switch out of the bracket leaving all wires connected. Install new switch in the reverse
order making sure the flat part of the shaft on the switch is lined up with the set screw hole. Use
the eraser end of a pencil to help with installation of the nut (E). With the new switch in place
remove wires one by one from the old switch placing them on corresponding terminal positions
on the new switch. Rotate the thumbwheel making sure that it clicks at the 10 and “0” position.
This will check that the switch is positioned on the shaft correctly. If not, start at the beginning to
position the switch correctly.
5. Install the completed assembly on the control panel with the washers and nuts (B). Make sure
that the thumbwheel is positioned so that it spins freely in the cut out of the panel.
6. Replace the panel on the kiln making sure that all the wires are still connected securely and
the wiring is not touching the relay and thumbwheel assembly.
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