Author Topic: Thermal Fuse for oscillating fan (Read 12594 times)

james_s · « **Reply #25 on:** July 23, 2018, 04:49:48 pm »

Start breaking things down into smaller sections (mentally) and test those. Follow where the wires go, draw a schematic on paper if that helps. Try checking continuity between each plug prong and whatever the other end of the wire connects to, check across the switch with it both off and on, you should see OL with it off and 0.0 with it on. Somewhere along the line you'll zero in on the open circuit. It's like locating a kink in a garden hose, you look at one part of the hose and see that it's plump so the kink must be downstream. You walk around the corner and find limp hose, so you start moving inward from each end until you find the spot where it changes from plump to limp and that's the clog or kink.

innkeeper · « **Reply #26 on:** July 23, 2018, 04:57:09 pm »

let us see which wire is not conducting, with the fan in the on position, do a continuity check from the thermal switch to each prong, my guess is one will read 0.0 and one will read o.l.

BayouBoy · « **Reply #27 on:** July 23, 2018, 04:58:52 pm »

I tested the prongs with switch on , then off... same reading 0.L. Also, not the type of plug that has a fuse in it.

james_s · « **Reply #28 on:** July 23, 2018, 05:01:58 pm »

Well keep checking things, with the switch on you should see continuity between the plug prongs, probably not 0.0, but not OL either. Somewhere you've got an open circuit, just keep narrowing it down.

BayouBoy · « **Reply #29 on:** July 23, 2018, 05:05:28 pm »

With switch on... one prong on thermal switch and one on prong. One prong reads 0.L, the other reads 294.0

BayouBoy · « **Reply #30 on:** July 23, 2018, 05:12:00 pm »

How will I know, based on the reading, when / where the short circuit is?

james_s · « **Reply #31 on:** July 23, 2018, 05:12:32 pm »

294 sounds like the resistance of the motor windings so that's a good sign, it means the motor is probably ok. So now what is between the points where you measured OL? The fault is somewhere between those two points.

james_s · « **Reply #32 on:** July 23, 2018, 05:13:50 pm »

The problem you have is not a short but an open. Open on your meter reads O.L., if you get that between any two points in the circuit then the fault is between those points. Anything other than O.L. can be assumed to be ok for the time being.

BayouBoy · « **Reply #33 on:** July 23, 2018, 05:15:06 pm »

The O.L reading was when I had a meter probe on each plug prong

james_s · « **Reply #34 on:** July 23, 2018, 05:17:28 pm »

Well, work your way up. Attach one probe of the meter to one of the plug prongs and keep it there for now. Follow the cord to the other end and touch the other probe there. If that gives you a reading then move to the next node and try there. You need a complete circuit from one plug prong to the other and somewhere along that loop you have a break.

BayouBoy · « **Reply #35 on:** July 23, 2018, 05:25:01 pm »

OK... I checked everywhere I could find a connection.. one probe on connection and one on plug prong. The only place I got 0.L was green/green & yellow wires (see photo). All other readings were 0.0.

innkeeper · « **Reply #36 on:** July 23, 2018, 05:40:33 pm »

the green wire is typically the ground wire, and the white and black go to the prongs. check to see if that white wire is connected to the prong you are getting the O.L. reading on to the thermal switch when the power switch is on for the fan bu doing a continuity check from that white wire to the plug.

BayouBoy · « **Reply #37 on:** July 23, 2018, 05:47:38 pm »

The white and black are crimped together, so not sure how to separate so I can test just the white. But... with switch on, one probe on black/white connection and one on plug prong, I get reading of 336.0

innkeeper · « **Reply #38 on:** July 23, 2018, 05:49:45 pm »

you do not need to, just test from the point they are connected together to the plug.

BayouBoy · « **Reply #39 on:** July 23, 2018, 05:51:32 pm »

Ok...that's what I did. Got a reading of 336.0

innkeeper · « **Reply #40 on:** July 23, 2018, 05:55:10 pm »

there are two prongs. give the reading to each individually.

BayouBoy · « **Reply #41 on:** July 23, 2018, 05:57:41 pm »

Oh, sorry... one reads 336.0, the other 0.L

innkeeper · « **Reply #42 on:** July 23, 2018, 06:04:20 pm »

ok so, the 336.0 is going up and though the motor.
the 0.L. would then be the connection out to the plug.

it sounds like you have a bad power cord.

lets double check, turn the fan switch off. then measure again from the white/black connector to each prong.
my guess is both prongs will now read 0.L.
if so, you have a break in the wire someplace between the white/black connector and the prong.

BayouBoy · « **Reply #43 on:** July 23, 2018, 06:08:54 pm »

You are correct.. with switch off, both prongs read 0.L. How can there be a break in the power cord, wires are insulated and in one piece.. If that's the case do I need to just replace the cord?

james_s · « **Reply #44 on:** July 23, 2018, 06:13:19 pm »

Wires can and do occasionally break inside the insulation. Let's do a few more checks to be sure though, measure between the crimp connection on the white wire and the plug. If you can't get a probe up inside the crimp cap you should be able to poke a paperclip or pin up in there to contact the bare wire.

BayouBoy · « **Reply #45 on:** July 23, 2018, 06:15:13 pm »

That was the test I just did.. Am I misunderstanding.. see previous post where both prongs read 0.L

innkeeper · « **Reply #46 on:** July 23, 2018, 06:16:58 pm »

yes, ... but I've found that many times the wire breaks either right at the point it enters the appliance or right at the plug. so many times I can just cut the plug off and hook up a new 3 prong plug from my local home supply.

since the cord is bad anyway ... you could do further testing by cutting the power cord an inch or two away from the plug and see if you get conductivity on the white wire to the white-black connection. if so, you could try and replace just the plug instead of the wire and the plug.

or just go get a new plug and wire and have done with it

james_s · « **Reply #47 on:** July 23, 2018, 06:19:35 pm »

One of my favorite tricks for locating a break in a wire is to connect it to a neon sign transformer and see where it smokes. Obviously not something I'd recommend for a beginner though.

innkeeper · « **Reply #48 on:** July 23, 2018, 06:21:38 pm »

Quote from: james_s on July 23, 2018, 06:19:35 pm

One of my favorite tricks for locating a break in a wire is to connect it to a neon sign transformer and see where it smokes. Obviously not something I'd recommend for a beginner though.

sounds like fun! .. but yea lets not give him any bad ideas

BayouBoy · « **Reply #49 on:** July 23, 2018, 06:24:39 pm »

OK..I cut the plug off and tested from black/white wire crimp to bare cut white wire.. still reads 0.L.. So replace power cord with new one that has same color wires (green, white , black)? Oh, and do I need new crimps or can they be reused?


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Author Topic: Thermal Fuse for oscillating fan (Read 12594 times)

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