Step 3: Thermal Fuse Replacement
Once the thermal fuse has been determined to be the cause, here we go...
Removing the Thermal Fuse:
Disconnect power to the fan before proceeding.
1. To make fuse replacement easier, we need to free the motor from the control unit keeping its wiring harness as long as possible. The harness has 5 wires going into the motor housing. By tracing this harness, starting from the motor housing, I found the Ground (green/yellow) and Neutral (blue) wires ending at a terminal block and another three (grey, orange, red) ending at the speed selector.
2. Remove the Ground and Neutral wire (no cutting required) from the terminal block. De-solder the grey, orange and red wires at the speed selector, note their location first. (You may have noticed that I cut the whole harness about 10cm from the motor…big mistake...but that was way before I decided to do this!!)
3. Using a flat tip screw driver as a lever, pry the motor housing mount rod away from the control unit.
4. Remove the oscillating unit and detach the capacitor.
5. Remove the metal housing screws. Carefully remove the rotor and the windings slowly by giving it enough slack from the harness.
6. The windings are tied by strings and coated with some kind of lacquer. We need to cut some of them (see the “X” points in the picture) using pen-knife or sharp tip scissors. Look for a bulge (where the fuse is) and notice where it ends.
7. Carefully slice open the black sheath cover to expose the brown woven sheaths, also tied with strings.
8. Trace the blue Neutral wire from the harness towards the windings. You will notice it ended inside the biggest sheath which is on top. This is our target. Cut the strings tying this sheath.
9. This big sheath, which is flattened, holds the fuse and another sheathed wire. Use fingers to lift it and press on its sides to form back its tubular shape.
10. With wriggle, press and pull action, slowly remove this sheath and the thermal fuse will be exposed. Put the removed sheath aside to be reused later.
11. Notice that one of the fuse’s leads is also sheathed to prevent electrical contact. Slice the SIDE of this sheath lengthwise about 10mm. Expose the lead through this cut.
12. With both leads exposed, cut them off as close to the fuse as possible. This will give us enough room to solder the new fuse.
13. Trim the leads of the new fuse to about 10mm and tin them with solder.
14. Solder the new fuse, polarity is not important but you may follow the old fuse direction.
15. Move the cut sleeve to cover back the lead exposed in step #11above.
16. Cover the fuse and its accompanying wire with the big sheath removed in step #10 above.
17. String the new fuse assembly to the windings as neat as you can. Fold back the black cover and string again. Ensure no string or black cover sheath is protruding into the rotor area.
18. Carefully place back the windings and rotor into the motor housing.
19. Secure the housing and mount back the oscillator and the capacitor.
20. Insert the motor housing mount rod to the control unit, a little pressure is needed here.
21. Dress back the wiring harness and reconnect the Ground and Neutral wires to the terminal block. (For me, I had to solder back all the wires and insulate them with heat shrinking tubes. I also had to de-activate the oscillator to prevent them from rubbing against each other)
23. Re-solder the grey, orange and red wires back to the speed selector.
24. Power on the fan to test. Cover back the control unit and you are done.