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


  7.105) Garbage disposal seizes repeatedly

A garbage disposal that doesn't have anything stuck in the cutting chamber
but seems to be hard to turn or will work with effort until left alone for
a day or two probably has a bad bearing caused by a leak at the shaft seal.
Of course, water gushing out of the lower part of the disposal (or *any*
amount of water dripping from inside the motor housing) is one indication
that there is a leak!  This also represents a safety hazard so the disposal
should be left unplugged and not be used even if it still runs.

By the time the leak is detected, it is probably too late to save the
disposal as corrosion of the steel shaft, excessive wear of the bronze
bushing, as well as possible electrical damage has already occurred.

Realistically, there is nothing that could have likely been done in any
case.  It is virtually impossible to repack such a bearing in such a way
to assure that a leak will not develop in the near future.

  7.106) Garbage disposal replacement (or upgrade)

My general recommendation is to get the approximately $100 1/2-3/4 Hp Sears (ISE
In-Sinkerator(tm) manufactured) unit when it is on sale (which is about every
week).  These now have at least a 4 year warranty.

If your previous garbage disposal was an ISE In-Sinkerator or Sears, then
replacement is usually a 10 minute job if the under-sink plumbing is in
reasonably good condition (doesn't crumble to dust when you touch it).
If the part that mounts to the sink is not corroded and not leaking, I
just leave it alone.  The only tools required are a screwdriver and wire
strippers (possibly) to move the power cord or cable to the new unit and
a screwdriver or socket driver and a large adjustable wrench or pliers to
unscrew the drain pipe and dishwasher connection (if used).  Complete
instructions should be provided with the replacement unit.

  7.107) Sump pumps and utility pumps

Sump pumps come in two major varieties:

1. Pedestal - a motor on top of a 3 foot or so pole drives an impeller at
   the bottom of its long shaft.  Only the base may be submerged.

   These motors are quite reliable but the bearing can rot/rust/sieze at
   the base where it may be under water or at least in a humid environment.

2. Submersible - a motor, usually totally enclosed in a sealed pump
   housing within an oil bath drives an impeller.  The entire unit
   is designed to be fully or partially submerged in the sump hole.

   The casing may leak at the bearing (if not magnetically coupled) or at the
   wire connections.  Repair of these motors is probably not worth the effort.

Utility pumps are often of the submersible variety.

Three types of automatic switches are commonly used:

1. Float/weight on a wire, rod, or string pulls on a spring action toggle
   type switch.  The length of the linkage is adjusted for the appropriate
   low and high water settings.  These will be used mostly with pedestal
   pumps.  If properly sized, this type of switch can be quite reliable - I
   have a sump pump using this type of switch which is easily 30 years old
   at this point without ever having any problems with the switch.

2. Mercury tilt switch sealed inside a rubber float.  By fastening its
   connecting wire to a suitable location, the level of the water will
   cause the float to pivot from horizontal the more vertical.  An enclosed
   mercury switch then controls power to the pump motor.  These are not
   serviceable but replacements are readily available.

3. Diaphragm pressure switch designed to sense the depth of the water from
   the trapped pressure.  As above, these are not really serviceable but
   can be easily replaced by the same or a mercury type (2).

Most common problems are with switches that are no longer reliable or totally
broken.  Universal replacements are generally available since the switch is
not usually an integral part of the motor/pump unit.

  7.108) Toys

Since there are a semiinfinite number of variations on electrically powered
toys, the only comment I have is that these are almost always combinations
of small PM motors, switches, batteries, light bulbs - and totally impossible
to identify electronic components.  With small kids, physical destruction is
probably a much more common occurrence than a part failure!

  7.109) Garage door operators

Typical garage door operators use a 1/3 to 3/4 horsepower induction motor
with a belt drive chain or screw mechanism to move the 'trolley' that actually
grabs the door.  A switch or pair of switches activated at each end of travel
stops the motor and toggles the state (up or down) of the controller.  Door
blockage sensors detect obstructions and stop or reverse travel.  A light
turns on with motor start and stays on for 3-5 minutes thereafter, controlled
by a simple timer.

Parts of a typical garage door operator (chain drive).  Details may differ
on operators with worm screw or other drive schemes.

1. Motor - single phase induction motor of about 1/2 horsepower at 862 or 1725
   (or so) RPM.  It is electrically reversible with a large ratio V-belt drive
   (probably about 25:1 for a 1725 RPM motor between motor shaft and chain

2. Chain or screw drive - often needs lubrication.  Make sure grease will
   not harden at low temperatures if relevant (e.g., Lubriplate).

3. Limit switches - set top and bottom positions of door.

4. Safety stop - a means of sensing when excessive force is required to move
   the door.  Some types use a compliant motor mount such that excessive
   torque will result in a twist which closes a set of contacts to reverse
   or stop the door.

5. Logic controller - a some relays or a microcontroller.

6. Remote receiver - a radio receiver tuned to the frequency of the hand
   unit.  Logic here or in the controller checks the transmission to 
   determine if the codes match.  More sophisticated units employ a
   pseudo-random code changing scheme to reduce the chance of code theft.
   This is usually in a box on the wall connected to the motor unit by a
   pair of wires.

7. Light bulbs and timer - in many Sears as others, the timer is a bimetal
   strip heated to operate a set of contacts.  The on-time is determined by
   how long it takes for the bimetal strip to cool.  These fail after about
   10 years but replacements are readily available.

  7.110) General garage door operator problems

1. No response from remote or local buttons.  Test power to both the motor
   unit and control box (they may be separate) outlets.  The operator or
   some other device might have blown a fuse or tripped a circuit breaker.
   Verify that the connection between the wall box and the motor unit is in
   tact - check the screw terminals on the motor unit - a wire may have fallen
   off.  Check the circuit breaker (red button) on the motor unit - an overload
   or an undetected cycling condition (an obstruction causing the door to keep
   going up and down continuously) may have tripped it.  Warning: pressing
   this button may result in the door starting to move immediately.

2. Local (inside) buttons work but remote unit is dead.  Check and/or replace
   batteries in the remote unit, confirm that the the code settings have not
   accidentally changed (unit dropped, for example), go through the set up
   procedure outlined in your users manual.  Find a cooperative neighbor with
   the same model and try their remote unit (after writing down their settings
   and reprogramming it for your door).  If this works, your remote unit is
   bad.  If this does not work, you have a receiver problem.

3. Motor operates (you can hear it) but door does not move.  This can be caused
   by a broken or loose belt, snapped door counterbalance spring, locked door,
   disconnected or broken trolley, logic problems causing the motor be turning
   in the wrong direction, and other mechanical problems.  If the motor
   runs for about the normal time, then the trolley is probably moving but
   not attached to the door.  If it runs until forever or the overload pops,
   then a broken belt is likely.

4. Door opens or closes part way and reverses, stops, or twitches back and

   * The tracks may need lubrication, there may be an obstruction like a broom
     that fell over into the vertical rails.

   * The gear timing may be messed up.  The upper and lower limits may be
     determined by switches operated from a cam separate from the trolley that
     moves the door.  If you just reassembled the mechanism, this is a likely

   * The safety stop sensors may be set to be too sensitive.

   * In extremely cold weather, the grease may simply be too viscous or just
     gummed up.

5. Door opens and closes at random.  There can be several possible causes:

   * A neighbor has a similar model and has selected the same code (probably
     the factory default - did you actually ever pick your own code?).

   * Interference from nearby high power amateur, CB, or military or commercial
     radio transmitters may be  confusing the receiver.  Suggest to them that
     they relocate :-).

     Are there such things as IR remote controls for garage door openers
     instead of the usual radio frequency variety?

   * The push button switch on your one of your remotes or receiver module
     is defective - a weak or broken spring - and it is activating the door
     due to vibration or just because it feels like it.  Test the switches.
     On the hand units, you can just remove the batteries for a day and see
     if the door stops misbehaving.

  7.111) Garage door operator light does not work correctly

Assuming the unit otherwise operates normally and you have tried replacing
the light bulb(s):

For many types (Sears, Genie, etc.), there is a thermally operated
time delay consisting of a coil of resistance wire, a bimetal strip,
and a set of contacts.  When the operator is activated, power is applied
to the heater which causes the bimetal strip to bend and close the
contacts turning on the light.  Due to the mass of the bimetal strip,
it takes a couple of minutes to cool down and this keeps the light on.

The most common failure is for the fine wire in the heater to break at
some point.  If you can locate the break, it may be repairable at least
as a temporary solution.  You cannot solder it, however, so a tiny
nut and bolt or crimp will be needed.  However, sticking contacts resulting
in a light that does not always go off are also possible.  Cleaning the
contacts may help.

This part is very easily accessed once the sheetmetal cover is removed.
It is probably somewhere in the middle of the unit fastened with three
screws.  Just remember to unplug the operator first!

Depending on the manufacturer, the original part may be available.  I
know that it is for Sears models.

You could also use a time delay relay or a solid state circuit (RC delay
controlling a triac, for example) but an exact replacement should be just
a whole lot less hassle.

  7.112) Garage door operator loses track of where it is

You press the button to close the door and it works fine.  However, next
time you press the button to make the door go up and it tries to go down into
the ground.

When it gets to the end of the track - be it at the top or bottom, there
must be something that it trips to shut down the motor.  At the same time,
this is supposed to set things up so that the next activation will reverse
the door.

Does the door stop and shut off when it reaches the end or does it eventually
just give up and trip on the safety?

When it trips the switch to stop at the end of its travel, some mechanism
is toggled to change the 'state' of the door logic so that it knows to
go up the next time it is activated.  It is probably this device - be it a
latching relay, mechanical two position switch, or a logic flip flop - that
is not being properly toggled.

I would recommend attempting to determine what device that switch is actually
supposed to toggle - it probably is in the operator unit itself (not the
control box).

  7.113) Garage door remotes behave differently

"I've got 2 Genie garage door remotes.  One of them works from about 100 yards
 away; the other I almost have to be right next to receiver.  I suspect that
 the antenna is the problem; either too short, or blocked by something."

First compare the antennas on the two remotes.  If they are the same and
there are no broken connections, your problem lies elsewhere.  The chance
of the wire itself being bad is pretty slim.

It could also be that the receiver and transmitter frequencies are not quite
identical.  If the remote units have been abused, this is more likely.  I
don't know about Genie but my (old) Sears has trimmers and I was able to
adjust it *very* slightly to match that of the receiver and boost sensitivity.

CAUTION: If you try this (1) mark the exact position where it was originally
and (2) do it only on the transmitter that has the problem.  This will minimize
the possibility of shifting the frequency to where it might interfere with
other devices.  See the section: "Adjusting garage door operator remote unit"
for more information.

  7.114) Adjusting garage door operator remote unit

This situation may arise if one hand unit operates normally but the other
has a very short range.  If you have only one hand unit, it might also be
the problem though not likely to have just happened on its own - either
it was improperly set up at the factory (if new) or hand unit was dropped
once too often.

It should not work at all if the switches are set improperly.  In such a
case, first test and/or replace the battery.  If this does not help, check
the switch settings.

The tuning is done via a variable capacitor trimmer (probably).

There will probably be a trimmer inside the hand unit (don't touch the one
in the receiver).  Position yourself at a reasonable distance and use a
plastic tool to adjust it until the door operates while holding the button
down.  The door will respond at increasing distances as you approach the
optimal setting.

Note: mark the original position first in case this has no effect!

This assumes there is an adjustment - if there is none, you may have an
actual electronic failure, bad connections, etc.

  7.115) Improving sensitivity of garage door openers receivers

Where a garage is constructed with aluminum siding, the remote signal may
be significantly attenuated and of insufficient strength to activate the
receiver module (inside the garage) of the opener at any useful distance
or at all.  Assuming the system operates normally otherwise (i.e., activation
is normal with the door open), two approaches (either or both together) can
be taken to solve this problem:

1. Locate the receiver module (well, actually, its antenna) in an area of
   unsided wood, glass window, or other non-metallic area of the building.
   Note that construction insulation may use aluminum foil as part of its
   vapor barrier so there could be problems even in an area with no siding.

2. Extend the antenna on the receiver module.  This may not always work but
   is worth a try.  A 1 or 2 foot length of copper wire may help dramatically.

3. There are external antenna kits available for some door openers.  The
   antenna goes outside, and connects to the receiver through a hole in
   the wall using coaxial cable.  You will probably have to go directly
   to the manufacturer of your garage door opener or a garage door opener
   service company.

  7.116) Universal remote/receiver units for garage door operators

So you lost your garage door remote or it got run over by your 4x4 :-).  Or,
it just expired due to age.  There are alternatives other than an entire new
operator if the remote is no longer available:

(From: Kirk Kerekes (redgate@tulsa.oklahoma.net)).

Go to a home center, and wander over to the garage door openers. Nearby,
you will find GDO accessories, and among the accessories will be a universal
replacement remote kit that includes a receiver, a transmitter and possibly
a power supply. For about $40, you can by and install the receiver in place of
the existing receiver. If your home center carries Genie openers, you can even
get an Intellicode add-on unit that uses Genie's scanner-proof code-hopping

  7.117) Garage door operator doesn't work reliably in cold weather

First, check the lubrication.  The most common problem is likely to be
gummed up grease in the chain drive (if used) or the bearings of the
rollers.  Note: the track itself generally doesn't require lubrication.
Increasing the safety override force settings may help but are not a wise
solution as the door will then be more of a hazard to any legitimate
obstructions like people and pets.

Another possibility is that the motor start/run capacitor has weakened
and is not permitting the motor to provide the proper torque.  You can
test the capacitor if you have a DMM with a capacitance scale or LCR meter.
Better yet, just replace it.

  7.118) Chamberland garage door opener repair?

"My remote broke for my very old (defunct) chamberlain automatic garage
 door opener.

 Chamberlain tech support told me they suggest I buy a whole new unit. Is
 there any other way to make my door usable with a different remote, or
 some other arrangement?"

(From: Panayiotis Panayi (panikos@mishka.win-uk.net)).

Which Chamberlain operator is it, i.e. which model number. You can
buy the handsets for Chamberlain operators up to 5 years old. If it
is older you will have to buy a new Rx & Tx for it. Most operators
have three screw terminals  on the back for the attachment of Rxs.
The old Chamberlain operators conformed to this. The new ones have
the Rx built onto the main PCB inside the operator and have 4
screws externally for pushbuttons and infra red safety beams. If
yours has 4 screws you will have to provide a separate PSU for the
new Rx or solder two pieces of wire after the step down
transformer on the PCB. You must do it before the rectifiers.
Otherwise the current drain from the Rx will be too big for them.
Besides almost all modern separate Rxs take 24 VAC.

  7.119) Garage door operator security

While manufacturers of garage door operators make excellent claims of
security, this is of no value if you don't take advantage of whatever
features are included in your unit. 

If there is access to your house from the garage, this security is even more
critical.  Once inside the garage, a burglar can work in privacy at their
leisure - and a nice set of tools is probably there for their convenience
in getting through your inside door!  Filling up a good sized car or truck
with loot - again in complete privacy - drive out and close the door behind.
No one will be the wiser until you get back.

1. DIP switches.  Many garage door operators use a set of 8, 12, 16, or
   more little switches to set the codes of the remote and base unit.
   If you have never set these, then your are probably still using the
   manufacturer's default - and all instances of the same model probably
   have the same code!  Change it to something random - pick a number
   out of a random page in a telephone directory or something like that.
   Do not select something cute - others, perhaps with not totally honest
   intentions - will think the same way.  You don't have to remember it so
   an arbitrary totally random setting is fine.  However, even the types with
   24 switches - that is over 16 million possible codes - can be sniffed:
   a relatively simple device can monitor your transmission as you open the
   door and program a special remote unit to duplicate it.

2. More sophisticated units incorporate a scheme whereby the codes change
   each time the operator is used in a pseudo-random manner which is almost
   impossible to duplicate.  Even sniffing such a code is of no use as the
   next instance is not predictable.

3. Don't leave your remote unit prominently displayed in your car - it is
   an inviting target.  Theft is not necessary - just a moment to copy down
   the switch settings may be enough.  Lock your car!  Also, leave a bogus
   remote unit in plain view (from your previous operator).

4. Just because the codes are secure doesn't mean that you are safe.  The
   keylocks that are present on many operators to open the door from the
   outside are pretty pathetic.  They can be picked in about the same time
   it takes to use a key - with ordinary tools - or often with any key that
   will fit the keyhole.  My advice: replace with a high quality pick
   resistant keyswitch.  A well designed electronic lock may be best.  When
   going away for an extended period, use the physical lock on the garage
   door itself as added protection and unplug the garage door operator.

  7.120) Identifying unknown transformer ratings in garage door operator

In a garage door operator, the transformer likely powers the controller
and receiver.  If you can look at where its outputs go, you may be able to
infer something about the voltage even if the transformer is a charred mass.

* If there are AC relays in the box, they almost certainly run off the
  transformer and their coil voltage will be the same if it is the only

* Check the capacitors in the power supplies of the controller and/or
  receiver.  They will give an indication of the approximate secondary
  voltage of the transformer.  Their voltage rating will typically be
  1.5 to 2 times the RMS of the transformer.

* Many of these transformers include a thermal fuse under the outer wrappings
  of insulating material.  These may fail from old age or due to a fault.
  If the transformer works fine without overheating when replaced (or bypassed
  temporarily on a fused circuit), then it may be fine.  However, shorted
  windings can cause a thermal fuse to blow and there is then no electrical
  test that will reveal the proper output voltage.

* Disassemble the transformer and count the number of turns of the primary
  and secondary windings.  The ratio multiplied by 115 is the output voltage.

* Get a 24 V transformer (it is probably not more than this) and connect its
  primary to a Variac and its secondary to the opener.  Slowly increase the
  variac  until everything works. (check every volt or so from 5 to 24).
  Measure the output voltage of the transformer, add 10-20%, you've probably
  got the secondary rating.  If it is near a standard value like 12 or 24,
  this is most likely correct.

* Buy a new opener.

  7.121) Electromechanical doorbells and chimes

Most of these consist of a low voltage transformer powered directly from
the house wiring providing 10 to 20 VAC at its output, one or more switches
for the front door(s), one or more switches for the back door(s), and an
electromagnetic chimes unit.

All of the switches for a given location (i.e., inside and outside the storm
door) are wired in parallel.  There will be three terminals on the chimes
unit - Common (C), Front (F), and Back or Rear (B or R).  This notation may
differ slightly for your unit.  Typical wiring is shown below.  An optional
second chimes unit is shown (e.g., in the basement or master bedroom - more
can be added in parallel as long as the bell transformer had an adequate VA

             Bell Transformer                         Chimes
          H o----+                                     Unit
                  )||       X      _|_ Front door        F
                  )|| +-----+------- --------------------o
                  )||(      |  
       115 VAC    )||(      |      _|_ Back door         B
   (Junction box) )||(      +------- --------------------o
                  )||(      Y                            C
                  )|| +----------------------------------o
          N o----+

* The primary side of the transformer is generally wired permanently inside
  a junction box.  This could be almost anywhere but the most common location
  is near the main electrical service panel.

* The common goes to terminal 1 of the transformer (the designation 1 and 2
  is arbitrary - it may not be marked).

* All the front door buttons are wired in parallel and this combination
  connects between terminal 2 of the transformer and the F terminal of the
  chimes unit.

* All the back door buttons are wired in parallel and this combination
  connects between terminal 2 of the transformer and the B or R terminal of
  the chimes unit.

Where the pushbuttons are lighted, a small incandescent bulb is wired across
the switch contacts and mounted inside the button unit.  It is unlikely that
this bulb will ever burn out since it is run at greatly reduced voltage.
However, if the button does not light but the bell works, this has happened.
Replace the pushbutton/light combination - locating a replacement bulb may
not worth the effort though Radio Shack is supposed to have something that
will work.

Most 'not-chiming' problems are due to the one or more of the following:

* Defective switches - these do go bad due to weather and use.  Test with
  a multimeter on the AC voltage range.  You should see the transformer voltage
  across the switch when it is not pressed and near 0 voltage across it
  when it is pressed.  If only one location does not work, a defective switch
  is likely.  Sometimes the wires just come loose or corrode at the terminals.
  These can be cleaned - with fine sandpaper if necessary - and reconnected.

  Note: where multiple switches operate the chimes from similar locations,
  multiple wires may be connected to each switch terminal.  Don' mix these up
  or lose them inside the wall!

* Bad connections.  These could be anywhere but unless you just did some
  renovation which may have damaged the wiring, the most likely locations
  are at the switches, transformer terminals, or chimes.  However, this
  sort of installation might have been done by just twisting wires together
  when extra length was needed and these can go bad.  They could be anywhere.
  Good luck finding the corroded twists!  Then, use Wire Nuts(tm) or solder
  them together to assure reliability in the future.

  If just a single location doesn't work, that should narrows down the problem.
  If only one switch does not work, first test the switch.  If disconnecting
  the wires from the switch does not result in full transformer voltage across
  the wires, then there is a bad connection between you and the transformer,
  the transformer has no power, is defective, or there is a short circuit

* Incorrect wiring at chimes unit.  This commonly happens when someone replaces
  the chimes unit and forgets to label the wires :-(.  It is often difficult
  to follow the wires since they pass through door jams, finished basement
  ceilings, and may not be color coded.  But checking it is easy to with a
  multimeter or the chimes themselves.  An assistant would be helpful - else
  you can just short across the front or back buttons as required below.

  1. Disconnect the wires from the chimes unit terminal block.

  2. Have your assistant press the front door button.

  3. Determine which pair of wires has full voltage - use the multimeter or
     touch them between C and F on the chimes unit.  Make a note of which ones
     they are.  One of these wires is will be C and the other is F.

     Note: due to coupling between the wires, there may be some voltage across
     all combinations.  The most will be across the relevant one (and this will
     be the only combination that will sound the chimes if you are using them
     as a voltage indicator).
  4. Have you assistant press the back door button.

  5. Determine which pair of wires now has voltage.

  6. Connect the wire that is the same as one of those in (3) to the C
     terminal, the other wire of the pair to B, and the remaining wire to F.

* Bad transformer or loss of power to transformer.  The transformer will
  often be located near the main service panel but not always.  Sometimes it
  is a challenge to locate!  To test, proceed as follows (this can be done
  with power on - the low voltage is safe but test first to make sure you
  have the correct transformer!):

  1. Disconnect one of the wires from its output terminals and then test across
     it with a multimeter on the AC voltage range.  There should be the full
     rated transformer voltage across these terminals (actually, it will
     probably be 10 to 20 percent greater).  The rated voltage of the
     transformer should be marked on it somewhere.

     - If there is voltage and it is approximately equal to the transformer's
       rated voltage, the transformer is probably good.

     - If there is none, check for a blown fuse, tripped breaker, or tripped
       GFCI; some other equipment may have overloaded the circuit.  Actual
       failure of the transformer blowing a fuse or tripping a breaker is

       A quick test to determine if the transformer is being powered is to
       feel it!  The transformer should be warm but not hot to the touch.  If
       it is stone cold, either there is no power or a bad connection in the
       input line) circuit.

     - If there is voltage and it is approximately equal to the transformer's

     - If the voltage is much lower than the rated voltage, the transformer
       may be bad.  In this case, it will likely be quite hot due to a short
       circuit inside.

  2. Assuming the voltage checks out, reconnect the wire your previously

  3. If it is now low or 0, there is a short circuit somewhere.  Note: a short
     on the secondary of this type of transformer will cause it to run quite
     hot but may not result in a blown fuse or tripped breaker or even any
     permanent damage to the transformer.

  4. If the chimes sound as you reconnect the wire, there is a short in or
     at one of the pushbutton switches or associated wiring.

  5. If the voltage remains the same, then the transformer is probably good
     and the problem lies elsewhere - bad switch, bad connection, defective

* Dirty or defective chimes.  Most common problems are not electrical but
  mechanical - the plungers that strike the actual chime or gong do not move
  freely due to dirt and grime (especially in a kitchen location) or corrosion.
  Usually, wiping them clean or some light sanding will restore perfect
  operation.  Do not lubricate as the oil will just collect crud and you will
  be doing this again in the near future.  If they move freely, then you have
  an electrical problem.  Also note that these chimes are designed to be
  mounted with the plungers moving vertically.  There is likely a 'this side
  up' indication on the unit - if you are experiencing problems with a new
  installation in particular, verify your mounting!

  Test for voltage between the Common and Front or Back terminals when the
  appropriate button is pressed.

  - If correct voltage is present, disconnect the non-common wire and check the
    resistance between the Common and the terminal for the chime that is not
    working - it should be reasonably low, under 100 ohms.  If the resistance
    is infinite, the coil is open.  Unless you can locate the broken wire, the
    chimes unit will need to be replaced.

  - If the voltage is missing, the problem is probably elsewhere.

  - If the voltage is low, there may be a partial short in the coil, the
    transformer may be underrated for your chimes (not all chimes take the
    same amount of power), or there may be a high resistance somewhere else
    in the wiring.

  7.122) Adding an additional set of chimes

There are at least two ways of doing this (though the first one is more
straightforward and intuitive and therefore generally preferred).

1. Locate the wires going to the first chimes unit.  There will be either 2
   or 3 (both front and back door).  Connect the new chimes unit to these
   same wires in parallel:

             Bell Transformer                         Chimes    Chimes
          H o----+                                    Unit 1    Unit 2
                  )||       X      _|_ Front door        F         F
                  )|| +-----+------- --------------------o---------o
                  )||(      |  
       115 VAC    )||(      |      _|_ Back door         B         B
   (Junction box) )||(      +------- --------------------o---------o
                  )||(      Y                            C         C
                  )|| +----------------------------------o---------o
          N o----+

   The only concern is whether the existing transformer that operates the
   chimes has enough capacity - you may need to replace it with one with a
   higher 'VA' rating (the voltage rating should be the same).  These are
   readily available at hardware and electrical supply stores and home

   Some people might suggest just paralleling an additional transformer across
   the original one (which may be possible if the output phases match).  I
   would really recommend simply replacing it.  (This is probably easier
   mechanically in any case.)  Unless the transformers output voltages as
   designed are identical, there will be some current flowing around the
   secondaries at all the times.  At the very least, this will waste power
   ($$) though overheating is a possibility as well.

2. Each additional chimes unit or group of chimes units can use its own
   transformer but share the doorbell pushbuttons.  Just wire point 'X' of the
   transformers together and each point 'Y' separately to the C (common)
   terminal on its respective chimes unit(s):

             Bell Transformer                         Chimes    Chimes
          H o----+                                    Unit 1    Unit 2
                  )||       X      _|_ Front door        F         F
                  )|| +-----+------- --------------------o---------o
                  )||(      |  
       115 VAC    )||(      |      _|_ Back door         B         B
   (Junction box) )||(      +------- --------------------o---------o
                  )||(      Y                            C         C
                  )|| +----------------------------------o    +----o
                  )||                                         |
          N o----+        From output Y of identical o--------+
                           second bell transformer
                           (H, N, X, wired in parallel)

   However, since the 'Y' outputs of the transformers are connected at all
   times to the 'C' terminals of the of the chimes units AND the 'X' outputs
   are tied together, any voltage difference between the 'Y' outputs will
   result in current flow through the chimes coils even if no button is
   pressed.  Thus, the transformers must be phased such that there is no (or
   very little) voltage between 'Y' outputs.  Test between 'Y' outputs with a
   multimeter set on AC Volts after you have the transformers powered: if you
   measure about double the transformer voltage rating (e.g., 32 VAC), swap
   ONE set of transformer leads (input or output but not both) and test again.
   If it is still more than a couple volts, your transformers are not matched
   well enough and you should purchase identical transformers or use the
   approach in (1), above.

Note: For either of these schemes, beyond some number of chimes units, the
current rating of the pushbutton switches will be exceeded resulting in early
failure.  However, this should not happen unless your house is similar in size
to Bill Gates' mansion.

* Another alternative:  If you have an unused baby monitor type intercom (your
  kid is now in college), stick the transmitter next to the main chimes and put
  the receiver in your workshop or wherever you want it :-).

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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]