Getting Power To Winding Floor Fan model # SFC1-500B

[lindylex]

I have the following fan motor model # SFC1-500B, 120V 60HZ 1.35A 162W. I am trying to figure out how to repair it. This is a learning project and not sure how to get past this part.

The red color wire has no continuity getting to the windings. I checked it from one of the prongs on the power cord. Th the power cord is connected to a red wire that goes to a white wire that goes to the windings. There is continuity to the white wire as you can see under the insulation that disrepair into the windings. I check the winding to see if there is continuity and I get none. I should be able to touch it with the multi-meter and get low resistance correct?

How do I check to see if the coil can receive power from the power cord? This seems like the most obvious way. If there a copper wire broken from the white wire located under the insulation?

 

[Nigel Goodwin]

As it says 'Thermally Protected' on the label I suspoect it's got a heat fuse somewhere (hidden in the windings?) and that it's blown.

 

[lindylex]

Nigel Goodwin, I searched for a heat fuse in the insulation of each wire. I cut them all open and found nothing. That is what I thought was going to be there.

 

[lindylex]

Here are some additional photos. I do not see a heat fuse anywhere.

 

[Nigel Goodwin]

In the bottom picture, at the bottom left, there's a pink component, that looks to be a heat fuse, and even looks to have 105C printed on it.

I presume you've spotted that?, and checked if it's OK.

 

[rjenkinsgb]

Nigel - looking at the previous photos, that appears to just be the printing on the connecting wires, as with the yellow in the first photo from post #4?

The only something-like similar fan motor I've had experience with had the thermal fuse brought out to its own connections and externally wired in series with the live feed to the motor.

 

[lindylex]

In the bottom picture, at the bottom left, there's a pink component, that looks to be a heat fuse, and even looks to have 105C printed on it.

I presume you've spotted that?, and checked if it's OK.

The wire with 105C written on it comes from the switch for one of the speeds. I was getting so hopeful. There is no heat fuse there.

 

[lindylex]

Nigel - looking at the previous photos, that appears to just be the printing on the connecting wires, as with the yellow in the first photo from post #4?

The only something-like similar fan motor I've had experience with had the thermal fuse brought out to its own connections and externally wired in series with the live feed to the motor.

rjenkinsgb, this is where I thought I might find this but there is nothing is series there. I have no continuity to the copper winding from the power supply. It just dives into the bundle of copper windings with no continuity.

 

[lindylex]

This feels strange. When I touch my multimeter on the same copper wire it show an open circuit. Why is this?

 

[rjenkinsgb]

Remember that the coil wire is insulated with a very thin layer of plastic or lacquer, which you should not remove.

The only places you should get any continuity readings are at the stranded connecting wires themselves or at the soldered joints between those and the coil wires.

Depending on the motor design, most or all wires may show some continuity voa the coils, or there could be two separate sets of coils with no direct connection between them. There may also be two wires connecting to nothing but the thermal switch, or that could be internal and part of one of the coil connections.

 

[lindylex]

Remember that the coil wire is insulated with a very thin layer of plastic or lacquer, which you should not remove.

The only places you should get any continuity readings are at the stranded connecting wires themselves or at the soldered joints between those and the coil wires.

Depending on the motor design, most or all wires may show some continuity voa the coils, or there could be two separate sets of coils with no direct connection between them. There may also be two wires connecting to nothing but the thermal switch, or that could be internal and part of one of the coil connections.

This is the answer I was searching for. "Remember that the coil wire is insulated with a very thin layer of plastic or lacquer, which you should not remove." I was not aware of this and makes sense why the multimeter has no continuity. Thanks for explaining this.

I searched everywhere for a thermal switch. It is nowhere to be found. Is it possible the thermal switch is embed within the copper windings?

 

[Nigel Goodwin]

This is the answer I was searching for. "Remember that the coil wire is insulated with a very thin layer of plastic or lacquer, which you should not remove." I was not aware of this and makes sense why the multimeter has no continuity. Thanks for explaining this.

I searched everywhere for a thermal switch. It is nowhere to be found. Is it possible the thermal switch is embed within the copper windings?

Yes it is, where it would be best placed to detect over heating - 'generally' thermal fuses are safety devices, and often never intended to be replaced once failed.

 

[lindylex]

Nigel, I have seen thermal fuses place in a very accessible place. Not in the copper windings before on other fans. It could have been placed next to the copper to detect the temperature. Why would they hide it inside the copper winding unless they are designing a fan to fail and not be easily repaired?

 

[andypandyplod]

They would put the thermal fuse in amongst the actual windings because this is the hottest place in the motor!. That is why the fuse is there in the first place to protect the motor from catching fire. The last thought on the makers mind is how can we put a safety device somewhere where it cannot be found or replaced. If they wanted to stop anybody being able to replace an item they would enclose the motor windings etc in an araldite type compound,and weld the two motor casings together.