# repairing hair dryer

A

#### Al

Jan 1, 1970
0
My boots were a little wet inside, so I put the nozzle of the blow dryer into
one. It ran okay. But when I manually shut it off after a minute or two, it
never would come back on again. Does that tell what is probably wrong with it?
If so, how to fix? Thanks.

I've taken it apart but there is no visible problem.

T

#### Travis Jordan

Jan 1, 1970
0
Al said:
My boots were a little wet inside, so I put the nozzle of the blow
dryer into one. It ran okay. But when I manually shut it off after a
minute or two, it never would come back on again.

Assuming the power cord, GFI and switch are OK, you probably blew a
thermal fuse that protects the heater elements from overtemperature.
Normally when this happens the blower will still run but the dryer won't
heat up.

K

#### Kevin R

Jan 1, 1970
0
Travis Jordan said:
Assuming the power cord, GFI and switch are OK, you probably blew a
thermal fuse that protects the heater elements from overtemperature.
Normally when this happens the blower will still run but the dryer won't
heat up.
not with my ones once it has blown a thermal fuse its dead

T

#### Travis Jordan

Jan 1, 1970
0
Kevin said:
not with my ones once it has blown a thermal fuse its dead

Sounds like that is the most likely cause, then.

A

#### Al

Jan 1, 1970
0
not with my ones once it has blown a thermal fuse its dead

wow, thanks to both for the quick replies. Here is a photo:
http://img233.exs.cx/img233/6205/fuse7sh.jpg

I had noticed what looked to be a bi-metal circuit breaker and another axial
component that I took to be something like a diode. But the 'diode' must
really be the thernal fuse, right?

So, I just used alligator clips to bypass the fuse and the dryer now works. Is
the other component (the block-like one in the right of the photo) a circuit
breaker?

What are the odds of me buying a thermal fuse locally? Or is it likely to be a
case where a $1 part needs to be ordered online, with$10 shipping. The fuse
looke to be green, with a white tip.

T

#### Travis Jordan

Jan 1, 1970
0
Al said:
What are the odds of me buying a thermal fuse locally? Or is it
likely to be a case where a $1 part needs to be ordered online, with$10 shipping. The fuse looke to be green, with a white tip.

If you are really in love with the hair dryer, I'd stop by a local
Salvation Army / Goodwill store and pick up the cheapest $2 hair dryer they have, and cannibalize the part. You'll probably want to crimp connect the new fuse (don't solder it in, for obvious reasons, unless you have REALLY good heat sinks). B #### Bob Shuman Jan 1, 1970 0 I have purchased these thermal fuses retail from Radio Shack for a couple bucks each. They usually have two critical ratings that you will need to use to find a substitute part. The first is a standard current limit which will be in Amperes and he second is a temperature limit, usually expressed in degrees centigrade. You rarely can match both exactly, so just get as close as possible without going over the previous values to retain the designed safety margins. If you can't get anywhere close, ask them to see the special order catalog or find a suitable replacement part on the web. Bob .. T #### Travis Jordan Jan 1, 1970 0 Bob said: I have purchased these thermal fuses retail from Radio Shack for a couple bucks each. Great information...I had no idea that RS carried these. The choices seem to be 128, 141, or 228 degrees (C). If I were the OP I'd take the lower rating which is 262 F. Should be "safe enough". R #### [email protected] Jan 1, 1970 0 i seem to recall this question came up only a few weeks back. Be sure to use the correct rated fuse and don't even think about leaving it bridged! A #### Al Jan 1, 1970 0 I have purchased these thermal fuses retail from Radio Shack for a couple bucks each. They usually have two critical ratings that you will need to use to find a substitute part. The first is a standard current limit which will be in Amperes and he second is a temperature limit, usually expressed in degrees centigrade. thanks. But I haven't been able to find a guide to the color ratings (on the web or in tbis group's archives), so as to know what temp I need. (It's apparently purple/lilac with white tip.) While on the subject, here are some recommendations for the faq, from an amateurs point of view (having never heard of "thermal fuse" until today): I had already read the faq's section on hair dryers before posting. It mentions "thermal protector" but not thermal fuse. The thing that eventually surprised me about this dryer is that there is not only a bi-metallic protector, but *also* a thermal fuse in series. Also, in the reverse, the section on thermal fuses does mention hair dryers. But a following section ("More on thermal fuses") gave me the impression they are all of some spring type. The one in my dryer is the kind pointed out here by Bob as being at RS, that look something like an axial diode. S #### Sam Goldwasser Jan 1, 1970 0 While on the subject, here are some recommendations for the faq, from an amateurs point of view (having never heard of "thermal fuse" until today): I had already read the faq's section on hair dryers before posting. It mentions "thermal protector" but not thermal fuse. The thing that eventually surprised me about this dryer is that there is not only a bi-metallic protector, but *also* a thermal fuse in series. Also, in the reverse, the section on thermal fuses does mention hair dryers. But a following section ("More on thermal fuses") gave me the impression they are all of some spring type. The one in my dryer is the kind pointed out here by Bob as being at RS, that look something like an axial diode. I'll add some clarifications. Thanks. --- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/ Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/ +Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm | Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html Note: These links are hopefully temporary until we can sort out the excessive traffic on Repairfaq.org. Important: Anything sent to the email address in the message header above is ignored unless my full name is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs. S #### [email protected] Jan 1, 1970 0 I have seen this and repaired it by replacing the part from an identical broken unit. Looking at a couple dryers in my house they have both the resetting thermal bimetalic type that resets after the unit goes over temp but then you also see the thermal fuse. Is it there because of reliability issues with the bimetal part? If so then it may have blown because the bimetal is faulty and (if you're like me and use it to shrink heat shrink) it may blow again. BTW I got a real heat gun, much better! Richard J #### Jim Adney Jan 1, 1970 0 What are the odds of me buying a thermal fuse locally? Or is it likely to be a case where a$1 part needs to be ordered online, with \$10 shipping. The fuse
looke to be green, with a white tip.

The color is no help, but sometimes there is a number on them which
might be the temp (but it could be in F or C.) Radio Shack used to
have 3 different temps of these.

Yours probably opened because it was sucking warm air that came back
from inside your boots and it overheated. The internal parts actually
got hottest AFTER you turned the blower off. The dryer is probably
fine. I would just replace the thermal fuse.

Yes, crimp them. Don't try to solder them.

-

J

#### James Sweet

Jan 1, 1970
0
The color is no help, but sometimes there is a number on them which
might be the temp (but it could be in F or C.) Radio Shack used to
have 3 different temps of these.

Yours probably opened because it was sucking warm air that came back
from inside your boots and it overheated. The internal parts actually
got hottest AFTER you turned the blower off. The dryer is probably
fine. I would just replace the thermal fuse.

Yes, crimp them. Don't try to solder them.

Probably was just the lack of airflow due to being stuck down into a boot
that did it rather than sucking hot air in the back. IIRC Radio Shack sells
two thermal fuses, try the lower temp one first, if it blows in normal use
then go with the higher one.

K

#### Ken Weitzel

Jan 1, 1970
0
Jim said:
The color is no help, but sometimes there is a number on them which
might be the temp (but it could be in F or C.) Radio Shack used to
have 3 different temps of these.

Yours probably opened because it was sucking warm air that came back
from inside your boots and it overheated. The internal parts actually
got hottest AFTER you turned the blower off. The dryer is probably
fine. I would just replace the thermal fuse.

Yes, crimp them. Don't try to solder them.

Hi Jim...

up; the terrible risks involved; and the many things we
find these thermal fuses in. (coffee makers, electric clothers
dryers, etc)

If - and that's a big if - it sucked hot air or even suffered
an almost complete lack of air input - then why oh why didn't
the thermostat open? (yes, I know, some of you are calling it
a bimetal thermal fuse, but what the heck - it's a non-adjustable
thermostat, right?)

I opened one of my grandkids to read the temperature rating
for the fellow previous to this occurence - and it the
"thermostat" one was sitting open and in plain view.
It does switch pretty good current - and it is in an airflow
that's warm, probably humid, and quite likely to corrode.
That I suspect would make it pretty easy to arc; and weld
itself closed.

I'm proposing then, that for the current poster, and the
ones that are surely to follow, that it might be worth
suggesting giving it a bit of a push with something to be
sure that the contacts aren't welded shut.

Just my 2 cents.

Ken

A

#### Al

Jan 1, 1970
0
I'm proposing then, that for the current poster, and the
ones that are surely to follow, that it might be worth
suggesting giving it a bit of a push with something to be
sure that the contacts aren't welded shut.

okay, that's a good point so I did that, Ken. It opened without any
discernable sticking. But, I notice this: current goes through the thermal
fuse, then splits in two. Part goes directly to the shorter run of heating
coils, and part goes to the bimetal component then on to the longer run of
coils . (The dryer has two switches and therefore four settings for temp.) So,
the bimetal can interrupt the longer series of coils, but not the shorter
series. The fuse cuts power to both.

I'd been thinking that the bimetal might open when the current running through
it gets too high, like a regular fuse. No? And conversely the thermal fuse
melts and opens from ambient, rather than internally generated, heat. That
doesn't explain what happened in the boot, though - unless the bimetal opened
and reduced heat, but the dryer was still chugging away on low heat until the
fuse melted. I don't remember, it wasn't recent.

I also can't figure why the fuse didn't melt until the dryer was turned off -
unless the coils were still radiating heat long enough after the airflow
ceased to take it away - as Jim and/or James seemed to be saying.

Also, I notice there is no soldering whatsoever anywhere that's in the tube
where the hot air flows through - as if the hot air might melt any solder
there. That's a surprise.

I uncrimped the fuse. There is no writing on it that I can see - so I'll go
with the lowest fuse I can get, as recommended.

B

#### Bob Shuman

Jan 1, 1970
0
Al said:
I also can't figure why the fuse didn't melt until the dryer was turned off -
unless the coils were still radiating heat long enough after the airflow
ceased to take it away - as Jim and/or James seemed to be saying.

Yes, this is the explanation. Once the blower was turned off, the airflow
ceased and the radiating heat had no where to go so the fuse opened at or
near its designated temperature.
Also, I notice there is no soldering whatsoever anywhere that's in the tube
where the hot air flows through - as if the hot air might melt any solder
there. That's a surprise.

Yes, this is also true. On the hair dryers, curling irons, and toaster
oveens that I have repaired, I have used a combination of crimping and
silver solder (it has a higher melting temperature). I only use a minimal
amount of this solder to assure a good conenction and have never had any
trouble doing this.
I uncrimped the fuse. There is no writing on it that I can see - so I'll go
with the lowest fuse I can get, as recommended.

You can probably estimate the current rating by dividing the maximum wattage
by the voltage. temperature will be the more difficult one to figure out.
Starting with lowest value is the best strategy if you can't determine the
actual value.

S

#### [email protected]

Jan 1, 1970
0
Hmm This is from:

http://home.howstuffworks.com/hair-dryer4.htm

"* A safety cut-off switch - Your scalp can be burned by temperatures
more than 140 degrees Fahrenheit (approximately 60 degrees Celsius). To
ensure that the air coming out of the barrel never nears this
temperature, hair dryers have some type of heat sensor that trips the
circuit and shuts off the motor when the temperature rises too much.
This hair dryer and many others rely on a simple bimetallic strip as a
cut off switch.

* A thermal fuse - For further protection against overheating and
catching fire, there is often a thermal fuse included in the heating
element circuit. This fuse will blow and break the circuit if the
temperature and current are excessively high. "

These thermal fuses are in a lot of things. I've seen them in motors,
esp fans if they're stalled or bearings get frozen no air flow temp
rises thermal fuse blows, no go. Some hair dryers also won't run if the
thermal blows or will run cold.

Richard

S

#### [email protected]

Jan 1, 1970
0
All,
Also on the subject of crimping. I know there are tools that will crimp
with tremendous force 10,000 lbs for instance to cold weld Cu and Al
wire together. I'm wondering if anyone has built or adapted a device
that will do that in the instance of what we're talking about here. I
know spot welding would also work well.
Richard

Replies
4
Views
2K
Replies
89
Views
24K
Replies
286
Views
18K
Replies
27
Views
2K
Replies
6
Views
1K