Notes on the Troubleshooting and Repair of Small Household Appliances and Power Tools


  14.25) Finding a replacement motor

In many cases, motors are fairly standardized and you may be able
to find a generic replacement much more cheaply than the original
manufacturer's part.  However, the replacement must match the following:

1. Mechanical - you must be able to mount it.  In most cases, this
   really does mean an exact drop-in.  Sometimes, a slightly longer
   shaft or mounting hole out of place can be tolerated.  The pulley
   or other drive bushing, if any, must be able to be mounted on the new
   motor's shaft.  If this is a press fit on the old motor, take extreme
   care so as not to damage this part when removing it (even if this means
   destroying the old motor in the process - it is garbage anyway).

2. Electrical - the voltage and current ratings must be similar.

3. Rotation direction - with conventional DC motors, this may be
   reversible by changing polarity of the voltage source.  With AC motors,
   turning the stator around with respect to the rotor will reverse rotation
   direction.  However, some motors have a fixed direction of rotation
   which cannot be altered.

4. Speed - depending on the type appliance, this may or may not be that
   critical.  Most induction motors run at slightly under 900, 1800, or 3600
   RPM (U.S., 60 Hz power).  DC motor speed can vary quite a bit and these
   are rarely marked.

MCM Electronics, Dalbani, and Premium Parts stock a variety of small DC
replacement motors.  Appliance repair shops and distributors may have
generic replacements for larger motors.  Junk and salvage yard or your
local dump may actually have what you want for pennies on the pound or less!

  14.26) Is motor rebuilding economical?

So you left your electric cement mixer mixing away and forgot about it - for
3 days.  Now the motor is a black charred ruin.  You can rent a jack hammer
to break up the cement but the motor is a lost cause.  The manufacturer has
been out of business for 20 years.  What should you do besides give the tool
a decent burial?

Here is a possible option for, in this case, a planer:

(From: Ed Schmitt (easchmitt@penn.com)).

I located a person who rewinds motors and had the job done for $60.00.
That was over 7 years ago, and the planer is still working.  Look around
and find some of our elderly craftsman who know how to rewind motors.
You'll save a bundle, and have a working tool.

(From: Michael Sloane (msloane@worldnet.att.net)).

That is an interesting thought - I have a 1942 Cat road grader with burned
out wiring in the 6 V wiper motor. Cat wants $200(!) for a new one, so I
would like to find someone who would rewind the old one (and make it
12 V at the same time).  I wouldn't even bother with the so-called
auto-electric guys, all they do is replace the brushes and diodes on
starters and alternators.

  14.27) Motor armature testing - or - what is a growler?

A common fault that cannot always be reliably identified with a simple
ohmmeter test is a couple of shorted turns in the winding that do not
affect the total resistance significantly.

A growler is basically an AC electromagnet exciting the windings in the
armature.  A shorted armature winding will act as a the secondary of a
transformer resulting in a high current flow and high induced magnetic field.

Hold a piece of spring steel like a hacksaw blade as a probe over the armature
as you rotate it slowly on the electromagnet.  A shorted winding will show up
as a strong audible vibration of the 'probe' - thus the name growler.

  14.28) Small motor repair and replacement

(From: mjsrnec (mjsrnec@prairie.lakes.com)).

Most motor shops won't bother with the universal motors because they are much
cheaper to replace than repair. However, if yours is a special be prepared to
pay standard rates for the service.  Email the Electrical Apparatus Service
Association found at: http://www.easa.com/  to find the EASA shop nearest you.

If you think the motor may be fairly common pick up a Grainger catalog or go
to: Grainger or: Grainger Universal Motor Index.

If this is for a power tool, contact the tool manufacturer for the authorized
service center nearest your location.

Chapter 15) Large Appliances

Editor's note:  Yes, I know this is supposed to be the "Small Appliance FAQ"
but so be it.  Until and if I write a "Large Appliance FAQ", this will have
to do :-).

  15.1) Web sites for large appliance troubleshooting

The following has complete diagnostic references for many major brands of
dishwashers, gas and electric driers, gas and electric ranges and ovens,
refrigerators, and washing machines:

* A-1 Appliance Parts - RepairNet Online Diagnostics

Here are some other sites with large appliance DIY repair info:

* Appliance Clinic
* Appliance Repair Net
* Garrell's Appliance Center

Also see "Sam's Neat, Nifty, and Handy Bookmarks" for additional large
appliance related Web sites.

  15.2) Electric oven calibration

If your cakes come out all drippy or your chicken breasts end up hard as a
rock and charred, this discussion is for you!  It is possible that the
thermostat on your oven needs calibration.  However, major errors in
temperature may be the result of a bad heating element, blown fuse or
tripped breaker, a door that doesn't close or seal properly, etc.  Confirm
that the oven is in otherwise good operating condition before attempting

The procedure given below assumes that your oven has a mechanical thermostat
which is still the most common type.  For an electronic thermostat - one in
which the set-point is entered via a touchpad - the adjustment (if any) will
likely be on the controller circuit board rather than under the temperature
knob.  If you do attempt calibration of an electronic thermostat, make double
sure that you have located the correct adjustment screw!

(Portions from: ken859@sprynet.com).

Most thermostats have a calibration screw located under the knob.  Try pulling
the knob off and look at the shaft.  Some shafts have a small screw located
in the center.  Rotating this screw will change the trip point at which the
thermostat will turn on and off.  This is determined by the sensor located
inside the oven itself.

You can also have your oven calibrated by an appliance service technician
by locating them in your yellow pages and have him/her make a house call but
you wouldn't be reading this if you wanted someone else to do it!

The following procedure can be performed by almost anyone who knows which end
of a screwdriver to poke into the screw head :-).

1.  Locate 2 thermometers that are oven safe and place them inside the oven
    on a shelf approximately in the center of the oven.  Make sure the actual
    sensing elements of the thermometers do not touch anything.

2.  Remove the knob from the thermostat and locate an appropriate screwdriver
    for the adjusting screw.  Re-install the knob.

3.  Turn on the oven and set it for 300 degrees F.  Allow it to come up to
    temperature (set light goes out).  Then wait an additional 10 minutes.

4.  Look at the temperature of the thermometers (averaging the two) and
    determine the error amount and direction.  Note: if the error is large
    (greater than, perhaps, 50 degrees F) then there may be a problem with
    the oven (such as a bad temperature sensor) which will not be remedied
    by calibration.

5.  Remove the knob and adjust the screw in the shaft one way or the other
    depending on which way the oven set-point is off.  If the direction is
    not marked to increase or decrease the temperature, just pick one - there
    is no standard.  You may be wrong on the first attempt :-(.

    Note: Rotate the adjustment in small increments!

6.  Place the knob back on the shaft. 

7.  Again wait 10 minutes after the oven set light goes off.  

8.  Look at the temperature of the thermometers and see how far off the error
    is now.  

9.  Repeat the steps above until this set-point is accurate.

10. Now set the thermostat to 400 degrees F and repeat the steps above for
    this setting.

11. The oven set-point should now be a lot closer to the actual temperature.

If you really want to be the oven to be accurate,  Turn the oven off and allow
it to completely cool.  The, repeat the above complete procedure 2 more times
or until the accuracy you desire is achieved.

Repeating this procedure may seem redundant but some thermostats because of
their mechanical nature have a margin of error.  Also due to the mechanical
nature, some settling of the parts inside does occur.

As long as the heating elements in the oven do not fail.  The oven should
maintain its accuracy for quite some time.  A simple check of the oven
once every 6 months or once every year will assure you that your baking
temperatures will be accurate.

  15.3) Heat control in electric range surface units

The typical electric range surface unit has two spiral elements.  In
older ranges, they are used in various combinations across the 120 and
240.  We have a GE range like this which has 5 heat settings (and off)
for each 'burner'.

Given 2 element and 2 voltages there are 8 possible connection
possibilities.  I don't know which 5 my GE range uses.

Newer ranges use a single element or just parallel the two elements and
use variable power control (pulse width modulation or thyristor phase
control) to obtain arbitrary heat levels and/or a thermostat to sense
the actual temperature.

BTW, this GE range is about 46 years old and still going strong (except
for the 1 hour timer which died about 5 years ago.)

(The following experiments from: Mark Zenier (mzenier@netcom.com)).

From my multiple renovations of my mother's stove of a similar vintage:

Warm is 120 volts applied to both elements of a burner in series.

Low is 120 volts applied to one of the two elements.  The burners are
wired so that they are not the same.  Half of the burners used the
center element, the others used the rim element.  Usually split between
front burners and rear.  (This is a GE, other companies used two
interleaved spiral elements.)

Third is 120 volts applied to both elements.

Second is 240 volts applied to one element, like Low, it varies 
from burner to burner.

High is 240 volts applied to both elements.

  15.4) Electric range top element does not work properly

If all the elements are dead, check for blown fuses/tripped circuit breakers.
There may be some in the range unit itself in addition to your electrical
service panel.

If one element is completely dead on all heat settings, the control is
probably bad or there is a broken wire.  If it is stuck on high for
all control settings or is erratic, the control is bad - replacements
are readily available and easily installed.

On ranges with push button heat selection, a pair of heating elements are
switched in various combinations across 120 and/or 240.  If some heat
settings do not work, the most likely cause is that one of the heatings
elements is burnt out although a bad switch is also possible.  Kill power
to the range and test the heating elements for continuity.  Replacements
are available from appliance parts stores or the places listed in the section:
"Parts suppliers".

  15.5) Improvised welding repair of heating elements

Due to the high temperatures at which they operate, welding may provide
better long term reliability of heating elements than mechanical fasteners.
However, in most cases, the following extreme measures are not really needed.

Warning: only consider the following if you are absolutely sure you understand
the safety implications of working directly with line voltage - it is not very
forgiving.  There is both an electrocution and fire hazard involved.

(From: Donald Borowski (borowski@spk.hp.com)).

I have had some success with welding heating element wires back together.
I did this on two toasters recently.

I extracted the carbon rod from a carbon/zinc D cell ('Classic' or 'Heavy
Duty' variety, alkalines do hot have carbon rods).  I filed one end to a point.

I wired a circuit as follows:

* Hot side of line to one connection of 1500 electric heater.

* Other connection of heater to carbon rod.

* Both connections of toaster under repair to neutral side of line, toaster
  turned on (to make connection).

* I twisted together the heater wires to be welded.

Then I touched the carbon rod to the wires, and drew it away.

There was a very brief arc, but it seemed to be sufficient.  It did take
several tries to get it right.

Of course, all safety warnings apply:  Dangerous power line voltages, welder's
mask needed for protect eyes, possible dangerous chemicals in D cell, etc.

This should work for other types of Nichrome coiled or ribbon heating elements
as well.

I vaguely recall seeing many years ago a suggestion of making a paste of
borax and putting it over the twisted-together ends.  I guess it was supposed
to act as a self-welding flux.  Anyone else recall this?

  15.6) Range, oven, and furnace electronic ignition

Many modern gas stoves, ovens, furnaces, and other similar appliances use an
electronic ignition rather than a continuously burning pilot flame to ignite
the fuel.  These are actually simple high voltage pulse generators.

* Where starting is manual (there is a 'start' position on the control(s), a
  set of switch contacts on the control(s) provides power to the ignition

  - A problem of no spark with only one control indicates that the fault is
    with it or its wiring.

  - A problem with continuous sparking even with all the controls off or in
    their normal positions indicates a short - either due to a defective switch
    in one of the controls or contamination bypassing the switch contacts.

* Where starting is automatic, an electronic sensor, thermocouple, or bimetal
  switch provides power to the ignition module as needed.

The Harper-Wyman Model 6520 Kool Lite(tm) module is typical of those found in
Jenne-Aire and similar cook-tops.  Input is 115 VAC, 4 mA, 50/60 Hz AC.  C1
and D1 form a half wave doubler resulting in 60 Hz pulses with a peak of about
300 V and at point A and charges C2 to about 300 V through D2.  R2, C3, and
DL1 form a relaxation oscillator triggering SCR1 to dump the charge built up
on C2 into T1 with a repetition rate of about 2 Hz.

           C1                A       D1                     T1 o
    H o----||----------------+-------|>|-------+-------+       +-----o HVP+
         .1 uF     D2 1N4007 |     1N4007      |       |  o ||( 
         250 V   +----|>|----+                 |       +--+ ||(
                 |           |                 |           )||(
                 +---/\/\----+                 |       #20 )||( 1:35
                 |  R1 1M    |             C2 _|_          )||(
                 |        R2 /           1 uF ---      +--+ ||(
                 |       18M \    DL1   400 V  |     __|__  ||(
                 |           /    NE-2         |     _\_/_     +-----o HVP-
                 |           |    +--+         |     / |
                 |           +----|oo|----+---------'  | SCR1
                 |       C3  |    +--+    |    |       | S316A
                 |  .047 uF _|_        R3 /    |       | 400 V
                 |    250 V ---       180 \    |       | 1 A
                 |           |            /    |       |
         R4 2.7K |           |            |    |       |
    N o---/\/\---+-----------+------------+----+-------+

Before you blame the ignition module for either lack of spark or continuous
spark, make sure the wiring is in good condition and completely dry and clean
(well reasonably clean!).  Confirm that proper voltage is reaching the module
with a multimeter or neon test lamp.  The modules are actually quite robust:

* Any liquid that may have dripped into the module may result in temporary or
  permanent failure.  Fortunately, as with the model cited above, it may be
  possible to pop off the bottom cover (with power OFF or the module removed!)
  and clean it.  The most likely failure would be the SCR if you are into
  component level repair.  Else, just replace it.

  WARNING: There are several capacitors inside that may be charged to as much
  as 300 volts.  The charge they can hold is probably not dangerous but may be
  painful or startling.  Discharge these before touching anything inside or
  attempting to check components.  Use a screwdriver blade or test clips and
  then confirm that they are discharged with your multimeter.

* Contamination of the controls from spilled liquid (did your tea kettle boil
  over?) may result in continuous activation of the ignition module since any
  electrical leakage across the switch contacts will likely be enough to
  activate it - only a few mA are required.  Remove the control panel cover
  and dry it out or unplug the range or oven for a couple of days.  If the
  contamination is not just plain water, it is a good idea to clean it
  thoroughly to prevent future problems.

* Spills into the area of the electrodes at the gas burner assembly may short
  out the ignition for ALL the burners since they probably use the same module.
  Again, clean and dry it out or let it dry out on its own (if just water).

These are probably standard modules and replacements should be available from
your local appliance repair shop or parts supplier.  An exact mechanical match
is not needed as long as the specifications are compatible.

  15.7) Replacing a thermostat

The following applies to refrigerators and freezers, air conditioners,
electric space heaters, as well as other small appliances.

Removing the thermostat (unplug AC line first!) and cleaning the contacts
using contact cleaner NOT sandpaper or a file - may help temporarily.
Replacement is easy if the cold control is self contained using a bimetal
strip.  If it uses a liquid filled bulb, the tube may snake around inside
the cabinet and may be more challenging. Still no big deal.  An appliance
part distributor or your appliance manufacturer should have a replacement.

  15.8) Oven door seal repair

(From: Brian Symons (brians@mackay.net.au)).

If you need a high temp silastic (e.g., for refitting glass windows in ovens)
then the Black silastic sold for car windscreen sealing from the local service
station or garage is the stuff.  Works well.  Someone here waited several
months and paid $80 for what he could buy down the road for $10 - it was even
the same brand.

  15.9) Freezer is normal but fresh food compartment isn't even cool

Some possibilities:

* The door is not properly closing for some reason.

* Someone messed with the controls accidentally.

* Something is blocking the passageway between the evaporator and the 
  fresh food compartment.

* The defrost cycle is not working and ice has built up in the evaporator
  coils.  This could be due to a bad defrost timer (most likely), bad
  defrost heater, or bad defrost thermostat.

* The interior light is not going out when the door is closed - that small
  amount of heat can really mess up the temperature (remove the bulb(s) as a
  test if you are not sure.

* Low Freon can result in problems of this type but that is a lot less likely.
  (These refrigeration systems are hermetically sealed (welded).  Slow leaks
  are unlikely.)

If you are handy, you can narrow down the problem and possible fix it - a
defrost timer can be easily replaced.  See the section: "Defrost system operation and wiring".

  15.10) Refrigerator not cooling after a week

First, clean the condensor coils.  It is amazing how much dust collects there
and interferes with proper cooling.

If you just turned it on a week ago and it is not acting up, a failure of
the defrost timer is quite likely.  On an old fridge, the grease inside
dries out/gunks up and restarting from cold results in it not running.
It takes about a week for enough ice to build up to be a problem.

This is a $12 repair if you do it yourself or $100 or so if you call someone.

Could be other things but that is what I would check first.  On a GE, it is
usually located at the bottom front and there is a hole in the front in which
you can poke your finger to turn it clockwise by hand.  Turn it until you 
hear a click and the fridge shuts off.  You should not get melting in the
evaporator compartment and water draining into the pan at the bottom.  The
fridge compressor should start up again in 10-20 minutes but I bet in your
case it won't as the timer needs replacement.

  15.11) Defrost system operation and wiring

The most common type of defrost system on a no-frost refrigerator or freezer
usually consists of:

* Defrost timer - motor driven (typically) switch which selects between the
  compressor and its associated devices (like the evaporator fan) and the
  defrost heater (located adjacent to the evaporator coils).  The timer motor
  likely only runs when the main thermostat calls for cooling.

* Defrost heater - resistance element located in the evaporator compartment to
  melt ice built up on the coils

* Defrost thermostat - closed when the temperature is below about 32 degrees F
  to allow current to flow to the defrost heater.  Shuts off once the ice melts
  as indicated by the temperature rising above 32 degrees F.

Testing: It should be possible to easily identify the bad components.  For
the following, it is assumed that the main thermostat is set such that the
compressor is on.

* Usually, it is possible to manually turn the defrost timer shaft (through
  a hole in the timer case) with a finger or small screwdriver - try both
  directions - one should rotate easily with a slight ratcheting sound until
  a distinct 'click' is heard.

* The click indicates that the switch has changed position.  The compressor
  should shut off (or start up if it was stuck in defrost).  Over 90% of the
  rotation range enables the compressor with a short time (e.g., 20 minutes)
  for defrost.  The total time is several hours (6 typical).

* At this point, the defrost heater should come on if there is enough ice to
  keep the defrost thermostat below 32 F.  You will know it comes on because
  there will be crackling sounds as ice melts and parts expand and the element
  may even glow red/orange when hot.  Water should start flowing to the drip
  pan.  If there is no sign of heating:

  - Test (with power off) the resistance of the element - it should measure
    under 100 ohms (31 ohms typical).

    If open - at the terminals of the element - it is bad.

  - Test (with power applied) for AC voltage across the element.  If there is
    none, test across the defrost thermostat - there should be none.  Or, test
    across the series combination of the defrost heater and thermostat.
    There should be full line voltage across the series combination.

    If there is still none, the contacts on the defrost timer may be bad, you
    may be in the normal cycle by mistake, the main thermostat may be defective
    or not calling for cooling, the wiring may be incorrect or have bad
    connections, or there may be no power to the outlet.

    If there is voltage across the defrost thermostat, it is defective or
    the temperature is above 32 F.  Confirm by jumpering across the defrost
    thermostat and see if the defrost heater comes on.

* If ice buildup is modest, the defrost thermostat should shut off the heater
  in a few minutes.  In any case, the timer should advance and switch to the
  normal position with the compressor running and defrost heater shut off in
  about 10 to 20 minutes.

  If the timer never advances, the motor is likely not running due to gummed
  up lubrication, a broken or loose gear, or a broken wire.  On some of these
  timers, the connections to the motor are to the moving contacts and break
  after a few years.  These can be repaired by soldering them to a more stable

  One indication that the motor is not being powered is for it to be ice cold
  even after several hours with the compressor (and thus the timer) being on.
  Normally, the coil runs warm to hot.  If the timer never advances even with
  a toasty winding, the lubrication is gummed up or a gear has broken.

Defrost timers are readily available at appliance parts distributors.  A
generic timer will cost about $12.  An exact replacement, perhaps up to $35.
If you call in a service person, expect to pay over $100 for the part and

Generally, the defrost timer is an SPDT switch operated by a cam on a small
motor with a 4 to 8 hour cycle (depending on model).  For an exact replacement,
just move the wires from the old timer to the same terminals on the new unit.
For a generic replacement, the terminal location may differ.  Knowing what is
inside should enable you to determine the corresponding terminal locations
with a multimeter.

The terminal numbering and wire color code for the defrost timer in a typical
GE refrigerator is shown below:

                     Black (4)
    Gray (3)      /o---------o Normal position - Compressor, evaporator fan.
H* o-----+------/
         |         o---o Blue (2)
       Timer           |         Defrost heater  Defrost Thermostat
       Motor (3180     o------------/\/\/\------------o/o----------+
         |    ohms)                 31 ohms          32 F          |
         |                                                         |
         | Orange (1)                                              |
         o---------------------------------------------------------+--o Common

   * H is the Hot wire after passing through the main thermostat (cold control)
     in the fresh food compartment.

  15.12) Compressor starting relays

Most refrigeration compressors use a current mode relay to engage the
starting winding of their split phase induction motor.  However, a
PTC (Positive Temperature Coefficient) thermistor might also be used.

A starting relay senses the current flowing to the run winding of the
compressor motor (the coil is a few turns of heavy wire in series with
the run winding) and engages the starting winding when that current is
above a threshold - indicating that the rotor is not up to speed.

A PTC thermistor starts with a very low resistance which increases to
a high value when hot.  Proper operation depends on the compressor getting
up to speed within a specific amount of time.

For testing only, you can substitute an external switch for the starting
device and try to start it manually.

CAUTION: Do not bypass a faulty starting device permanently as the starting
winding is not intended to run continuously and will overheat and possibly
burn out if left in the circuit.

Assuming you have waited long enough for any pressures to equalize (five
minutes should do it if the system was operating unless there is some
blockage - dirt or ice - inside the sealed system), you can test for proper
operation by monitoring the voltage on the start and run windings of the
compressor motor.  If there is line voltage on both windings and it still
does not start up - the overload protector switches off or a fuse or circuit
breaker pops - the compressor is likely bad.

  15.13) Changing the temperature range of a small refrigerator

It is simple in principle.  The cold control - the thing with the knob -
needs to be modified or replaced.  It is a simple on/off thermostat. 
You may be able to figure out how to adjust its limits (mechanical) or
simply locate a suitable thermostat and install it in place of the
existing unit.  Note: if it uses a capillary tube to a sensing bulb, don't
attempt to modify that part - it is sealed and should remain that way.
The mechanism it operates may still be adjustable.  However, you will
likely loose the low end of your temperature range.

  15.14) Washer sometimes spins

When it should be spinning, is the motor running?  Does it complete the
cycle in the normal time?

I would guess that the solenoid to shift it into spin is binding or
erratic.  Thus opening the door gives switches it on and off like the
timer but since it sometimes works, it sometimes works by cycling the
door switch.

  15.15) Clothes washer does not fill (cold or hot)

This assumes the unit has power and otherwise operates normally.  However,
determining this may be difficult if the completion of the cycle is dependent
on a water weight or volume sensor.

There are several possibilities:

1. The appropriate water inlet filter is clogged.  This will be accessible by
   unscrewing the hose connection.  Clean it.

2. The solenoid is bad.  If you are electrically inclined, put a multimeter
   on the cold water valve to see if it is getting power.

3. The temperature selector switch is bad or has bad connections.

4. The controller is not providing the power to the solenoid (even
   for only hot or cold, these will have separate contacts).

  15.16) Window air conditioner preventive maintenance

Very little needs to be done to get many years of service from a typical
window air conditioner.

Of course, clean the inside filter regularly.  This is usually very easy
requiring little or no disassembly (see your users manual).  Some slide
out without even removing the front cover (e.g., Emerson Quiet Kool).

I generally do not bother to open them up each year (and we have 4).
Generally, not that much dirt and dust collects inside.  A cover during
the winter also helps.

Use a vacuum cleaner on the condenser coils in the back and any other easily
accessible dirt traps.

If you do take the cover off, check the fan motor for free rotation.  If
it is tight indicating bad bearings or lack of lubrication, it will have
to be disassembled, cleaned, and lubricated - or replaced.  If there are
lubrication holes at the ends of the motor, put a couple drops of electric
motor oil in there while you have it open.

These units have a sealed freon system - so if anyone's been into it
before - you can tell from obvious saddle valves clamped on.  Generally,
if it cools and the air flow is strong, it is OK.

These units tend to be very reliable and low maintenance.

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Written by Samuel M. Goldwasser. | [mailto]. The most recent version is available on the WWW server http://www.repairfaq.org/ [Copyright] [Disclaimer]