Using all the helpful hints I could find on the subject of "Dryer not
heating" and checking out all other components it is looking like the
centrifugal switch on the motor may be the culprit. Can anyone tell me how
to test it? I assume the motor has to be running. Do I take the drum out,
remove the belt and let the motor run? I'm assuming that there should be a
wire to the heater element that should show voltage only when the motor is
running? I'm also guessing that it will only be 120V at the motor. I don't
have any diagrams, so if anyone can tell me how to locate the right wire, I
will be really grateful. As you can probably see, I'm working at the upper
limit of my ability. Unfortunately, I just put a bunch of money in this
machine because it is less than 4 yrs old. If I had known that I would have
a different problem just a month later ...... well, you all know what I'm
saying. Thanks to all. What a great, helpful site!
Are you sure there is no schematic in the machine? I have always
found one tucked somewhere in the unit usually in the top part where
the controls are located. It's going to be difficult describing what
to look for without specific information on the dryer. Check sears
parts website and see if you can at least find a parts breakdown of
the dryer, it may lead you in the right direction.
Thanks for your response. I'm at work and the machine is at home, but I'll
give it another look. I have checked the Sears site. Unfortunately, their
diagrams are not very detailed and somewhat generic. They show a "motor-
drive" and a "switch-motor". I guess that is good, since I read one place
that the switches are sometimes built into the motors and you have to replace
the motor it the switch goes bad. If I find a schematic, how do I test? Do
I remove the drum and belt and test the wires leading out of the motor to the
heater element? Even if the switch is built in, there should be some wires
leading to the element, right? With the motor running, I should detect 120V
along that wire, right? If not, is the switch bad? Any advise will be
Message posted via HomeKB.com
It's hard to say without seeing a schematic. Without finding one or
creating one by tracing things out, you are working blind. There are
many things that can cause the issue you are having. Checking a
switch is best done when the switch is de-energized, out of the
circuit, manually activated, using a continuity tester. This may or
may not be possible with the appliance you have. If you are working
at the upper limit of your capability be very careful poking around
The centrifigal switch typically controls the motor start capacitor. If the
motor runs but the dryer does not heat, I would look elsewhere. I.e., there
are usually several thermostats which can fail, preventing power to the
heating element. A simple VOM test will find the problem.
Many dryers have a switch for the heat controlled by the motor
centrifugal switch. Get rid of the dust and lint around the motor and
see if the mechanical part of the switch works. You may be able to
replace the switch without replacing the whole motor.
There should be a schematic pasted on the back of the dryer.
Also, it would help if you can give us the model number. There should be a
data plate just inside the
Trouble could be anything from a bad circuiit breaker (one "leg" open"), bad
centrifugal motor switch,
bad thermostat, bad wire, or many other things.
If a bad motor switch, it is replaceable w/o replacing motor.
See an example: http://www.repairclinic.com/0081.asp?RccPartID 25
Thanks to all for your replies and suggestions. The model no. is 110.
The switch looks exactly like the one at the repairclinic.com link that you
sent. On the advice of many helpful folks, I have checked the circuit
breaker. I've checked the outlet - 120V on each side. I've checked the
thermal fuse, the thermostats, etc. for continuity. I've removed the heater
element and wired it to an extension cord and it gets hot. I've checked the
timer and it is sending 120V down to the heater. It seems the only piece
left is the motor switch, but I'm looking for advice on how to test it. If
it only works when the motor is running, do I remove the drum and test it
with a voltmeter to see if it is sending 120V to the heater? There are 8
wires on the switch. The wires on no. 1 and 2 are red and much heavier gauge.
Since the wires going to the heater are also red and much heavier, I'm
assuming that it is one of these two wires. I'm assuming that the wire
should have no voltage if the motor is not turning. If the motor is turning
and the switch is working, it should have 120V. If the motor is turning and
the switch is bad it should have no voltage. Is there another condition
where the motor would have no voltage? Am I on track to testing the switch?
It's a lot of money to put into a new switch, if the old one isn't bad.
Thanks again to all.
Message posted via HomeKB.com
OK, I just dove in and measured all the wires into the switch, but I'm not
sure what it means.
Using the picture at the repairclinic.com link:
With the motor off, terminals 1, 2, and 6 measured 120V. Terminals 3, 4, and
5 measured no V.
With the motor turning, terminals 1, 2, 5, and 6 measured 120V. Terminal 3
measured 40V. Terminal 4 measured no V.
The wires at terminals 1&2 are red. The wire at terminal 3 is purple. The
wire at terminal 4 is blue. The wire at terminal 5 is white. The wire at
terminal 6 is black. Behind terminals 4 & 5 are two more wires (same color)
that lead back into the motor.
Does anyone have any idea if this means anything? Should there be more than
40V at terminal 3? Should terminal 4 measure some V?
If nobody has any advice, it looks like my ever more impatient wife is going
shopping for a new dryer and I've wasted $100 + on recent repairs.
Message posted via HomeKB.com
It doesn't mean too much w/o knowing which wire goes where -- the color
isn't necessarily standardized between vendors or even models of the
same vendor so that info doesn't help much.
Someone else posted sample diagrams and a verbal description of how the
circuit is wired -- using that you should be able to trace your wiring
and figure out which terminal is what function.
The way to tell whether the switch is functional is to check continuity
(w/o power to the output contacts of course) when running -- they should
be open at rest, closed when not.
Certainly a shop should be able to test it for you if you can't. I'm
sure these guys fail, but I'll note as a sidelight that I've had dryers
run for 20+ years and that has never been a failure mode yet for me...
Of course, if the switch isn't all that expensive anyway, there's the
"swap it out and see" technique as well....
Thanks for the response. Unfortunately the switch is $65-70, so just
changing it out is not an appealing option.
I'd like to try to test the switch as you recommend. Are you saying check
continuity betwen terminals 1 and 2? How do I get the motor to turn w/o power?
All suggestions are appreciated.
I don't know that they are 1 & 2 w/o either a diagram or tracing the
circuit (I didn't look at what was posted by the other respondent, I'm
just talking general testing). What you're looking for are the contacts
that complete the power to the heater element (outputs) when the motor
The power to feed the elements isn't supplied through the motor, so it
should be possible to run it w/o there being power on the contacts
(outputs) to the heating elements. There will, of course have to be
power to the motor and it's outputs to the input coil of the relay.
But, if you can't trace the wiring and understand which terminals are
what, you shouldn't be trying this and ought to either call the service
tech back out or take the motor/switch to a service center at let them
Of course, you should be able to simply apply power to the input coils
irrespective of the motor running and check whether the output contacts
close w/o the motor running at all. Whether it is full 110 VAC input or
the 40 V you measured is from an inductive pickup depends on how it is
designed or whether you measured something immaterial like a drop across
a coil or motor windings or whatever. Since you didn't give any
references as to what reference any of the measurements were taken,
they're again of little, if any, value.
You are not the first to state that this switch is probably not the problem.
The only reason I ended up focused here is because it was the only suggestion
so far that I could not rule out. If you look at the beginning of the thread,
you will see that I have checked the continuity on the various thermostats,
the thermal fuse, heater, etc. I have checked for voltage from the timer. I
have checked for voltage from the 240V receptacle. I welcome any other
suggestions you may have, because I don't want to buy another dryer, but
after 2 1/2 hrs at the washateria, wife is growing impatient with my attempts
to fix. This might be a dumb question, but could any of the thermostats or
the thermal fuse be bad and still show continuity? As a previous urgent
attempt, I bit the bullet and purchased a new thermostat - the one in the
blower plenum. It mounts on a "heater" (a small black component with a hole
in it where the thermostat sits). I purchased a new heater as well. These
two components may work together to monitor the moisture in the clothes.
Anyways, there was some chat about these being likely to fail and when I
examined them there was a lot of what looked like white powdery residue on
both components. They both showed continuity, but I was hoping for an easy
and somewhat inexpensive fix. No such luck. I'm growing more desperate, so
I need your suggestions on other places to check. Many thanks for replying.
AE Todd wrote:
Message posted via HomeKB.com
Yes, the red wire supplies power to the heating element. When the motor
reaches speed,it closes the contacts between 1 & 2, and supplies 240V across
the heating element.
Did you finds the schematic on the back of the dryer?
Here's a sample schematic:
Basically the heater element circuit is a 240V series circuit starting at
L1, thru an airtemp selector switch, thru a
normally closed limit switch, thru the operating thermostat, thru the high
limit T-stat, thru the heater element, thru the
motor centrifugal switch contacts between 1 & 2, and completes the circuit
to L2, providing 240V across the element.
I have no idea what your troubleshooting capabilities are, so I won't give
you step-by-step instructions that
might put you at risk for electrical shock.
BTW, I assume you have unplugged the dryer, and used your volt meter on the
250V scale or higher to make sure that you
have 240V available at the receptacle across L1 & L2.. If not, you need to
Thanks for responding. No luck with the schematic. I tried the sears site
and they list a wiring diagram, but don't offer it for sale.
I have checked the outlet and I have 240V there.
How do I test to see if the switch is closing at speed? When I probed the
switch with my multimeter, I found 120V at both 1 and 2, when the motor was
off and when it was turning. Is that normal?
My troubleshooting skills are probably a little above the average homeowner.
I have some tools and I'm good at following instructions. I have good
mechanical skills, but specialized electrical knowledge is minimal.
As a last resort measure, would a shop be able to test it, if I removed the
motor & switch and took it in?
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