(Sorry about the huge images)

My friend's dehydrator stopped working last night after a power outage, with zero electronics knowledge i decided to take it apart and play with it. After taking it apart i plugged it in connected to just the fan (which is what wasn't working before) and it seems to work now. The problem is, i can't put it back together. I can get the fan to run, but i'm not sure which cables need to go where so that the fan and the heater both work.

I'm not sure how obvious all of this is but the white cable with the copper wires is the plug into the wall.
The blue and black wire coming out of the copper motor are to the fan.
The white, red, and black wires all belong to the "heater". The black wire is connected to a little knob so that you can increase or decrease the temperature.







Even if i can't fix it, i would appreciate the opportunity to learn a little more about how these things work (eg. what that thing that looks like a battery is and what it's there for, why there are wires connected to both sides of it, etc.).

If anyone can help me figure this out, i'd really appreciate it Smile
Any idea what i need to do to complete the circuit for the heater? From first to last, there's the red, white, and black wires. I really should've taken a picture of them first Sad Heh..
chickendude wrote:
(Sorry about the huge images)

My friend's dehydrator stopped working last night after a power outage, .... i plugged it in connected to just the fan (which is what wasn't working before) and it seems to work now. ... I can get the fan to run, but i'm not sure which cables need to go where so that the fan and the heater both work.


Ignoring the fact that you don't know what you're doing find the power supply. It's likely built in where the wall cable enters the unit and test that. Perhaps with a multi-meter. It's the likely point of failure and fixing it may be more challenging than you're willing to tackle.

If the power supply does not function, take it a part and you might see a few resistors a few sizes too big. Kind of like the Grinch on Christmas or something. Replacing those would require finding the right ones and desoldering the existing ones and soldering on new ones. Even then, other things might have suffered damage and it still might not work.
Well i don't think there's anything really broken, i think it was just a loose wire or something. My friend said that it was heating up but the fan wouldn't run, now the fan is running but i can't put the wires back together. I've tried several different combinations that i thought would work, but the heater doesn't come on. I tried connecting the heater directly to the power source and it would heat up but i think it was overheating so i quickly unplugged it. So i think both parts (heater and fan) work, i just can't figure out which wires go together.

The heater seems pretty simple, it seems like it's really just a long piece of metal. One end has a knob to control the temperature, but other than that there's not really anything. Is that little piece in the last picture the resistor? I'm not really sure why there's a wire connected on both ends of it. And from what i can tell, it doesn't appear to be soldered in. It's possible that there's something wrong with the temperature knob, but i've gotten it to pass current through the heater to the fan. I'll pull out my multimeter tomorrow and play around with it a bit, thanks for the suggestion (i'm a little embarassed i didn't think of that earlier, haha).

Thanks for the response/help, comicIDIOT.
Oh, okay. I wasn't able to discern if the heater worked too. If you mentioned it previously I overlooked it, sorry about that. This is where my knowledge get's iffy but get a hold of a multi-meter still and touch both the wires with each end of the MM. You should be able to tell which wire is which by doing so.

But I'd get a second opinion on that Very Happy
Thanks, i'll do that tonight. One thing i'm unsure about is that there are 7 wires, so one set of wires has to have three wires together rather than just two. I'm also still unsure why the resistor (i believe that's what it is in the last picture) has two wires attached to it. I would've thought that you'd just have it on one side, then the current would run through the metal piece (the "heater") and then to the black wire on the other end, or do i have it backwards?

And does it matter what wire from the power source goes where? I imagine it does, like a battery's positive/negative side, but i'm really not sure.
chickendude wrote:
Thanks, i'll do that tonight. One thing i'm unsure about is that there are 7 wires, so one set of wires has to have three wires together rather than just two. I'm also still unsure why the resistor (i believe that's what it is in the last picture) has two wires attached to it. I would've thought that you'd just have it on one side, then the current would run through the metal piece (the "heater") and then to the black wire on the other end, or do i have it backwards?


Quote:
And does it matter what wire from the power source goes where? I imagine it does, like a battery's positive/negative side, but i'm really not sure.


It certainly does.

I'd also hazard a guess that the red and black wires from those last two pictures connect to either the fan or the heating element. Without seeing more detail, it looks like those springs might even be the heating element so it could be that one or both of those wires connect to the fan at some point.

You might be able to type the model number online and find pictures of the wiring.
chickendude wrote:
Is that little piece in the last picture the resistor? I'm not really sure why there's a wire connected on both ends of it.
That piece is either a thermister, which measures temperature, or a thermal fuse, that will disable the dehydrator if it gets too hot. I'll try to get around to puzzling over those photographs tomorrow.
Thanks again everyone, work's been super busy lately and i haven't had a day off at all this month, i still haven't played around with the multimeter yet (i've been watching some basic electronics tutorials on Youtube before going to bed).

And there are three wires in the last two pictures, they're connected to the heater. I'm not quite sure what the red wire is doing, it seems like the power should flow from the white wire to the black wire (or vice versa) passing through the little resistor knob and the part Kerm mentioned in his last post, the thermister/thermal fuse.

As i said, the fan is pretty straightforward, there are two wires, so it's pretty easy to figure out.

I just did a little bit of research and it appears that piece is indeed a thermal fuse. Someone posted a video to Youtube (http://www.youtube.com/watch?v=8yI-o8qWdqU) for another model (i believe the one my friend has is an FD-75PR) but the basic setup looks the same. Unfortunately it's a bit blurry so you can't see the wires very clearly, but it's a nice starting point. I also found a post on fixya which gives this advice:
Quote:
This is how mine is wired (same brand perhaps a different mode)l:
1. Connect one side of the household current (big white wire) to the part going into the knob for the temperature control (the rheostat )
Put on one of the twisty plastic caps.
- Now variable current is going into the heating elements.
2. Find the two wires coming out of the heater part.
One carries the juice, the other goes back to complete the circuit.
(Red & black are always IN current - white & blue are always return wires to complete circuits coming OUT of a device)
3. Connect the black motor wire to the red (juice carrying) wire from the heater. (put on a twisty cap) Now you have variable current going INTO the fan.
4. Connect up the rest to the other part of the big white plug to complete all the circuits. (should all be white or blue) Put on a twisty!
I'm a little unsure about it, though, as it seems that the red and black wires are on opposite sides of the heater circuit, though the white wire could very well be the out current. Summarizing from that, here's what i understand:
1. One of the wires carrying the power from the wall connects to the black wire that runs to the rheostat (temperature resistor). Cap #1
2. Connect the black wire from the fan motor to the red wire from the heater. Cap #2
3. Connect the blue wire from the fan motor, the white wire (the "out" from the heater), and the other power wire. Cap #3

I still don't quite understand what that red wire is doing, but if i'm not too exhausted i'll test this out tomorrow after work.

EDIT: Ahh today i tried that configuration and i think it overheated or something, the little metal springs lit up and burned right off, so i think this project is, uh, over.. Whoops!
  
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