Why the "resistor with Thermal Link" in Fan-Tastic Fan? - Fiberglass RV


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Old 10-24-2017, 06:24 PM   #1
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Why the "resistor with Thermal Link" in Fan-Tastic Fan?

I'm having trouble (again) with my Fan-Tastic Vent ceiling fan. I have a 2009 model (#H4000R, perhaps new model number is 1250). The specs for the fan say it has a ""3-speed-and-Off resistor switch with Thermal Link".
Why the resistor? Why the thermal link? What do these do? Do they work like another fuse, but a fuse that can't be replaced? I'm beginning to suspect that something in my system is disabling/burning out the resistor or the thermal link and won't let my 3-way switch turn on. Fan-Tastic already sent me a replacement, so I want to figure out if I'm somehow burning these switches out as soon as I install them. Or maybe the replacement switch they sent was faulty? (It happens, but rarely). Anyway, maybe if I understood what the resistor does and how the "thermal link" works, I'd make better progress. Electricity 101 anyone? I can use the guidance.
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Old 10-24-2017, 07:56 PM   #2
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The three speed switch incorporates low value resisters at two of the settings that simply reduce the voltage and slow the fan at two of the switch settings. The third switch setting has no resister and therefore runs the fan at the full voltage of your 12 volt system, which is basically the battery voltage or converter output. The resisters are heavy duty so I doubt they failed, although offhand I don’t know what they are rated at. I am pretty sure that the “Thermal Link” is basically a fuse that cuts the power in the case of an overheat. You could bypass it and see if it was the cause of a failure, but at the moment I don’t know where it would be on the Fantastic Fan (see EDIT below). Some of them also reset after a time.

So my question is what problem are you having with the fan? What is your troubleshooting, repair and replacement history?

If you simply replace the entire Fantastic Fan then that should solve the problem. But there might be other trouble shooting steps that might make a complete replacement unnecessary. For example, the dome lid switch is one of the more common failure points. Again, you can bypass this switch and if the fans then runs, you know that only the switch needs replacement.

EDIT: Oh, I see the thermal "fuse" in the the switch assembly. I replaced my switch with a speed controller so I can adjust the fan speed infinitely from zero to 100 %. In this photo of my FF that I took before the mod, I have circled what must be the thermal fuse.
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Old 10-24-2017, 08:00 PM   #3
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Originally Posted by Richard Davis View Post
I'm having trouble (again) with my Fan-Tastic Vent ceiling fan. I have a 2009 model (#H4000R, perhaps new model number is 1250). The specs for the fan say it has a ""3-speed-and-Off resistor switch with Thermal Link".
Why the resistor? Why the thermal link? What do these do? Do they work like another fuse, but a fuse that can't be replaced? I'm beginning to suspect that something in my system is disabling/burning out the resistor or the thermal link and won't let my 3-way switch turn on. Fan-Tastic already sent me a replacement, so I want to figure out if I'm somehow burning these switches out as soon as I install them. Or maybe the replacement switch they sent was faulty? (It happens, but rarely). Anyway, maybe if I understood what the resistor does and how the "thermal link" works, I'd make better progress. Electricity 101 anyone? I can use the guidance.
The 3 speeds are made possible by adding different value resistors in series with the motor. This effectively changes the voltage that the motor sees. Highest speed has zero resistance and should always work. But all of this needs the "fuse" to be intact. (thermal link). Fuses blow for a reason. Does this fan have a 'reverse' capability? Have you ever reversed it while it is still spinning? That draws a lot of current and guess what happens?
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Old 10-25-2017, 04:27 AM   #4
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The resistors are just coiled nichrome wire. Visual inspection should tell you if they are good. In any case they are not in the circuit on high speed and as such not the problem. The thermal fuse is there to protect from overheating. They are common in circuits that use heating elements such as electric coffee pots and hair dryers. A continuity test should tell it's condition. The reverse switch has a center off position. Could that be the problem? The switch could be dirty. Try a little contact cleaner. The lid switch opens when the lid is closed to prevent the fan from coming on. A continuity test will tell if it is functioning correctly. Do you have a multimeter. If not, it's time to buy one. You can test continuity and measure voltage with one. Any hardware store, auto parts store, Walmart, Home Depot will sell them., Get one with a digital readout. The ten dollar version is fine. Good luck, Raz
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Old 10-25-2017, 06:44 AM   #5
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Three years ago I added a $4.00 PWM controller to my fantastic fan after trying additional resisters to slow the speeds and lower the noise. Now I have variable speed, less noise and lower energy consumption, and no hot resistors wasting electricity. It is one of the best mods if your fan doesn't already have variable speed. You can see the fgrv thread here.

Cheers, john

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Old 10-25-2017, 07:39 AM   #6
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idea

john great idea if I ever get mine running I will install one of those so simple!!


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Old 10-25-2017, 07:21 PM   #7
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Not sure what problem you are having. Resistors limit current flow across them. You have two resistors of different impedance (current restriction) so each will run your fan at a different speed. The third setting (high speed) likely doesn't incorporate a resistor so your fan gets full power. The (thermal) fuse has a filament that melts to open the circuit and cut the current to prevent overheating in other parts of the circuit and prevent fire. If the fuse blows you likely have a short in your circuit which you need to locate and fix.
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Old 10-26-2017, 08:52 PM   #8
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Many thanks for all the helpful responses. I just haven't been able to put them to practical use yet. Maybe tomorrow! Seriously, just being able to understand what is supposed to be happening in the electrical world helps me, even if in itself it doesn't solve the problem.
I now understand what the resistors are and what they are intended o do. Makes perfect sense. I'm still uncertain about the thermal link and how it works differently from the fuse that is in the fan unit, but is not a part of the 3-way switch itself. I will test the continuity of the thermal fuse, Raz, and see if it is the problem. Thanks for the idea. There is a reverse switch, but it has been replaced and does not appear to be the problem. I own a multimeter, but that doesn't necessarily mean I know how to use it (rather like my fiddle....) Widgetwizard, I have never knowingly reversed the fan direction while it was in operation, although I'm not the only person on this planet. Gordon, you ask what problem I'm having. A simple one: nothing happens when I turn it on. Fan-Tastic sent me replacements for the 3-way-switch, the reverse switch, and the lid switch because I was experiencing this same problem a year ago. I've replaced everything and STILL can't get the fan to turn on! Thank goodness I don't need it much, but still.... If I connect the two wires coming from the fan directly to the battery, the fan works. (I've only done that for a split second, just to determine that the fan itself wasn't the culprit). I've by-passed the dome/lid switch to determine if THAT is the solution -- NOPE. I've tried to by-pass the 3 way switch as a key step in trouble-shooting the problem and finding the culprit, but I'm not sure I've figured out how to do that. Any suggestions? I have a wiring diagram from Fan-Tastic, so I THINK I have all the connections (which have been off and back on a zillion times now) on properly. And I have voltage coming INTO and OUT of the unit from the black and white wires emerging from under the rat fur on the ceiling. I'm really stumped but ain't dead yet
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Old 10-26-2017, 10:39 PM   #9
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A resistor reduces current flow. A fuse protects the circuit from overload. A thermal fuse protects against overheating.
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Old 10-27-2017, 05:14 AM   #10
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Post the wiring diagram.. I have one and it is likely the same, so I could point out where to check voltages... but you should post the wiring diagram that we know is correct so there are no errors.

Basically follow the power from where is comes in, and along the route it takes to the fan (through fuse and fuse holder, switches).

BY the way, when you bypassed the dome switch how did you do it and what were the results?
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Old 10-27-2017, 07:00 AM   #11
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fuses and such

You can limit current flow but you are still using a lot of current in those cases lost through heat! Finally after awhile those things give it up!

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Old 10-27-2017, 12:21 PM   #12
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wiring diagram

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ID:	113166 Not sure about this, but here's a stab at showing the diagram. Gordon, I first replaced the dome switch, but with no effect on the fan. Then I connected the white wire that normally comes out of the fan motor (and goes to the dome switch/plunger) and connected it directly to the reverse switch instead. Again, no effect. I had to use a longer wire to make that by-pass, but I used the same gauge as the wires currently installed.
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Old 10-27-2017, 01:18 PM   #13
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Different ways to approach this. I would connect voltmeter negative lead to point Z, then with positive lead follow the black wire and check for voltage at A, B, C, D, E, and F with switches in all combinations and the dome cover always open.
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Old 10-30-2017, 05:55 PM   #14
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It took me a while to see your letters, Gordon! Still haven't found Z. But if I connect a lead at A (that's the bottom of the devise that holds the fuse) and connect the other lead to D, I get a reading of 12.64 volts (which is pretty close to what I get at the battery). BUT I ONLY get that reading with the three-way switch set as OFF. If I turn it to 1, 2, or 3, I lose any voltage. That's with the reverse switch turned ON to either IN or OUT, but turned ON. If I connect the second lead to C, instead of D, I lose all voltage, regardless of where the switch (or the reverse switch) is set. That would suggest (to this electrically-challenged brain, any way) the 3 way switch is at fault. However, I've checked the continuity of the thermal fuse that is a part of the 3-way-switch as Raz suggested and it seems sound. Worse yet, if I by-pass the 3-way switch by attaching the leads that attach to D and C, nothing happens to the fan. Puzzler....
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Old 10-30-2017, 07:55 PM   #15
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"Z" on the diagram is the lower left corner of the 'in/out' reversing switch, its where the white (-) lead comes into the fan.
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Old 10-30-2017, 08:42 PM   #16
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Where's Waldo! Good spotting, John! I'll give that a go.
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Old 10-31-2017, 03:13 PM   #17
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So before I bore all you helpful folks with vast possibilities of voltage numbers, let me ask: When I take the readings as Gordon suggests (now that I have located Z), do I just touch the probe to the wire where it is still connected to the electrode (?) on the various switches? Or do I disconnect the wire from the electrode and place my probe on the loose wire itself? the naked electrode itself?
Also, when I put my multimeter's negative alligator clip on Z, do I put it on the electrode with the ground wire still connected, or do I disconnect the ground wire from the electrode and put the multimeter's negative alligator clip on the wire only? or perhaps even on the naked electrode Z itself?
I need to verify this, as thus far, my tests suggest I have voltage except when the 3-way switch is turned to OFF, which kind of makes sense, but then why doesn't the fan spin?
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Old 10-31-2017, 04:59 PM   #18
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those tests should all be done with the circuit hooked up normally. the point is to follow the voltages, and see why they aren't getting to the motor (or if they ARE getting to the motor, then the motor itself is bad).
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Old 10-31-2017, 05:00 PM   #19
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note, btw, the exact voltage isn't important, whats important is that voltage is present.
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Old 10-31-2017, 05:12 PM   #20
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Many thanks, John. That's what I had done, but since it still wasn't showing any obvious problem points (well, obvious to me anyway....), I thought I'd better check with the better informed. I'll run the check one more time and see if my results show anything significant. By the way, I have twice hooked up the two wires coming/going to the fan directly to the battery using jumper cables, just to see if the fan motor is the problem, since I couldn't find any other source. I've only run the fan for a second each time, but it spins like a top.
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