Instructables

Removing hair dryer heating element

Request for help:  Does anyone know how to remove the heating element from a hair dryer to have it only blow cold/cool air?  I've opened it up and there are a lot more wires than I expected.  I have just enough electrical knowledge to be a little bit above dangerous, so I thought it would be best to ask for help.  Thanks!

Picture of Removing hair dryer heating element
HairDryer001.jpg
WaffleM (author) 1 year ago
Using Jack's method above, the motor reads about 13V. Could I just wire a simple switch and an AC to DC adapter (wall wart type) to the motor? Like the ones pictured at the top of this page:
http://www.mcmaster.com/#ac-to-dc-voltage-transformers/=ilamco

If that would work, I'm thinking that I would select one of the 12VDC adapters or the 15VDC one. How can I figure out which power output to choose?

Thanks for all the help.
The blower motor there looks like a permanent magnet DC motor
http://en.wikipedia.org/wiki/Brushed_DC_electric_motor
and just based on its size and appearance I am going to guess that motor would want to be supplied with something in the range of 6 to 24 volts DC, if it were being powered by a DC supply.

Moreover, I am going to guess that the way this hair dryer is wired, is that that motor and its bridge rectifier (4 diodes) are wired in series with one of the heating elements, so that most (say 90%) of the mains voltage (guessing that is about 110 VAC where you live) falls across the heating element, and a much smaller fraction (10%) falls across the bridge rectifier and motor.

A way to confirm this hypothesis would be to solder two sense wires across the motor.  Then put the hairdryer back together, feeding those  sense wires out to your voltmeter.  That way you can look at the DC voltage across the motor, while the hairdryer is running.  I am guessing the voltage across the motor will not be higher than about 20 VDC.

Another way to do this, is to just start by assuming my guess is correct, then seek out a new DC supply for the motor.  I mean try to find a DC supply, like maybe an old computer power supply, or a DC adapter, or power brick, or whatever you've got in your junk box, that looks like it could supply between 6 to 24 volts DC, at a current of maybe 1 or 2 amperes.    Then you can just directly connect that supply to the motor, and see if you can make it run at a speed that both you and the motor are happy with.

Also thought I'd mention:  suggestions to replace the heating element with a resistor are naive. Why?  Because a resistor would dissipate just as much power as heat.

So I think you're going to be looking for a replacement power supply for that blower motor. Like I suggested before:  6 to 24 volts DC, at a current of maybe 1 or 2 amperes.

Then you put it all back together, without the heating element, and I think that will do what you want:  blow room temperature air, and consume less electrical power.
Hack42Moem2 years ago
I did that once and when I tried switching the thing on afterwards, it gave up the ghost. It's possible (in my very limited understanding) that the heating element serves as a resistor, that cannot safely be removed without replacing it.

I'm no electrics wizz, so take this for what it's worth. I'm sure someone will be along to help you.
this sounds reasonable. since the dryer won't know that you took the coil out it's going to try to still supply juice to the coil. without the resistance of the coil it's going to cause problems.

if you could find the resistance value of the coil, you might be able to put in a resistor of equal value that wouldn't heat up, or at least wouldn't heat up in such a way that it would heat up the air.

though, they do make hair dryers that have a cold setting...and your dryer's switch block looks a lot more complicated than the normal on/off hi/lo type
Still the dryer couldn't have the motor and heating coil in series or the motor would have never started . Hmmm just thinking out loud......if parallel, it'd still show up as some resistance in the circuit, but that;d be small. Hmmm, It also looks like, on the slider switch, that one setting has red/black opposite each other, and the next setting has them reversed ! There has to be another resistance or some other way to liimit power to the coils for medium and low heat settings.
Thanks. I was hoping for that to make sense.

since the dryer won't know that you took the coil out it's going to try to still supply juice to the coil

That is a great way of putting it.
Pro

Get More Out of Instructables

Already have an Account?

close

PDF Downloads
As a Pro member, you will gain access to download any Instructable in the PDF format. You also have the ability to customize your PDF download.

Upgrade to Pro today!