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Al
Guest
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 Posted:
Thu Feb 10, 2005 11:07 pm Post subject:
Re: repairing hair dryer |
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On Thu, 10 Feb 2005 06:14:13 GMT, Ken Weitzel <kweitzel@shaw.ca> wrote:
| Quote: | 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.
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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.
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Bob Shuman
Guest
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| Posted:
Fri Feb 11, 2005 1:27 am Post subject:
Re: repairing hair dryer |
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"Al" <none@no.com> wrote in message
news:420c8e90.5767063@news.individual.net...
| Quote: | On Thu, 10 Feb 2005 06:14:13 GMT, Ken Weitzel <kweitzel@shaw.ca> wrote:
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.
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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.
| Quote: | 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.
| Quote: |
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.
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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. |
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Guest
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| Posted:
Fri Feb 11, 2005 1:44 pm Post subject:
Re: repairing hair dryer |
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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
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Guest
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| Posted:
Fri Feb 11, 2005 1:55 pm Post subject:
Re: repairing hair dryer |
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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 |
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