Kenmore/Marvel Ice maker

Some reverse engineered service information including photos, schematics, and theory of operation recorded while servicing a kenmore/marvel/whirlpool icemaker.

Model No 76709894250
Serial 052692035
I suspect that while this stand alone Icemaker was sold under the kenmore name, it was made by Marvel and the icemaker assembly itself was made by whirlpool. This same icemaker assembly is apparently found in stand alone and built in icemakers in many models. This icemaker makes chord (in the mathmatical sense) shaped cubes.

Theory of operation (approximate)

I have not verified that things work in exactly this sequence.

• We will begin in the hold position. The timer contacts on the motor interrupts its own power to stop in this position. Presumably, in order to leave the hold position, BOTH of these conditions must exist: the bail (bin full sensor) must be down and the icemaker portion thermostat must indicate the "cubes" are frozen.
• The timer begins rotating, which also rotates the tines of the ejecter arm which scoop out the cubes since the ejecter arm is connected directly to the timer gear.
• Apply heat to melt the cubes enough to free them from the tray.
• The tines hit the ice cubes.
• The tines may stall in this position until the heat melts the cubes enough that they can be removed.
• The tines continue to rotate, starting to move the cubes
• Heat is removed
• The bail is lifted by a cam on the timer gear in preparation for dropping the cubes.
• The cubes drop
• The solenoid valve is actuated, filling the tray with water. It apparently operates for a set period of time which is adjustable by a screw on the side of the timer box.
• The solenoid valve closes
• The bail is dropped, sensing the new height of ice
• repeat.

Note that since the feeler contacts which follow the contacts on the timer cam are not located along a common radius, which makes it more difficult to interpret the timing sequence from the cam itself.

Thermostat

This paragraph not finished and may not be correct: The thermostat contacts close when the tray gets cold enough. With the bail down, During almost all of the timer positions, except hold (where it spends most of its time), the thermostat operates the heater. Thus, it keeps the ice tray from over freezing. In hold mode, the heater and the motor are put in parallel and neither operates until the thrmostat closes (i.e. the water has frozen), at which point the motor starts and the heater also turns on.

Wires Feeding Icemaker

• GRN (Ground)
• Brown (Solenoid)
• White (Neutral)
• Black (Hot)

Manual overrides

• Short M to N to Start Cycle
• Short V to L to force solenoid valve (under some circumstances, this might short L to N, which would not be good - don't do it if the bail is up or the timer is turning).

Timer Gear Contacts

Listed in inside to outside order

• N - (Neutral)
• M - motor
  This contact is normally shorted to N (neutral) to provide power to the timing motor. At one section in the cycle, it is connected to H instead.
• H
  related to the heater.
• V - Solenoid valve
  This is shorted to H at one point in the cycle. There is a plastic adjustment screw on the right side of the timer box that adjusts the dwell time. Since this contact has a diagonal edge, moving the feeler arm side to side will vary the on time.

A few odd features of the timer gear: One of the contacts has a diagonal edge to allow for a timing adjustment. There is also an unconnected contact area that preceeds this to make a smooth transition. Timer contacts have leading edges which bend down so they wont be caught and pulled loose. A couple contacts have little ski jump ramps at their tail ends - this is to prevent shorting between the adjacent contacts without any dead time between contacts (which might be bad since this is the contact that provides power to the timer motor itself). There are little gaps in some of the contacts that are two narrow to cause an interruption in the current. These are probably to wipe the feeler contacts and remove debris.

Timing gear removal: First, mark the relative orientation of the gear and the shaft with a marker- you don't want to get it on 180 degrees out of phase. Pull hard on the edge of the gears while squeezing the tabs on the shaft together with needlenose pliers. You need a lot of force (I sort of wedged my fingers so they exerted force between it and the timer body).

Schematic

This schematic does not include the refrigerator itself (compressor and its thermostat).

Water Supply

A clogged water supply line is a common problem. I use one of those thin plastic supply lines and I get about 1 gallon per minute of flow if I test using a bucket.

Timer sequence

ANGLE N M H V
----- - - - -
    0 ===         Bail raising
   30 ===         Bail raising, Ejector <---O
   60 ===         Bail up                                   ice starts dropping
   70 === . .     Bail up        
   90 === ===     Bail up                                   Water fill
  120 ===         Bail up,      Ejector straight up
  130 ===         Bail drops
  150 === .       
  170 . ===                                                 Hold position
  180 === .                     Ejector  O---->
  210 === .                     Ejector hits ice
  240 === . 
  270 === .      
  300 ===                       Ejector straight down
  330 === 
  350 ===         Begin Raising Bail

= shorted
. one contact made, but not two

This sequence was obtained by the following proceedure, which may be helpful for people with other models or to double check my work or repeat it with greater precision.

• unplug ice maker/fridge
• Mark timing gear postion relative to shaft so we don't reassemble backwards. Note that the shaft may rotate due to the weight of the ejector bail once you remove the gear, so you need to mark the position relative to the shaft.
• Remove timing gear
• cut a square of transparent plastic, with a hole in the center
• Mark the front (towards gear) vs rear side of the plastic
• Place plastic over the shaft and contacts on the timer assembly
• Mark the straight up position on plastic
• Mark the position of each contact
• Mark the direction of rotation with an arrow
• Remove plastic
• Label each contact on the plastic
• Place the plastic over the back side of the timing gear with the hub through the hole with the "front" side facing gear so you are looking through from the "back" at the contacts
• Line up the timing mark on the gear with the straight up mark
• Rotate the gear and look at where the contacts are contacting and record this information
• Remove plastic
• Partially assemble gear back onto shaft. Make sure you don't install 180 degrees out of phase; use the marks you made earlier. Do not seat the gear far enough to engage the gear on the timing motor. This allows you to rotate the gear by hand (clockwise only) and observe the mechanical actions.
• Record the actions of the bail and ejector arm

Troubleshooting

• No cubes, cubes to small, cubes made very infrequently
  
  • Make sure there are no improperly ejected ice cubes, frost, etc. jamming the ejector arm.
  • Make sure the sensing bail is not in the up position.
  • Check water supply
  • Check if solenoid is operating correctly
  • Have you tried the dwell time adjustment on the right side of the timer assembly?
  • Try Defrosting unit
  • Are the cubes being made but not ejected? Check heater ejecter arm, and if timer rotates.
  • Bad thermostat never detects when cubes are frozen?
• Water Overflow
  Reduce pressure on water supply line. Reduce valve open dwell time.
• The "cubes" aren't clear
  • If the cubes are whitish, this is normal for home icemakers due to disolved air.
  • If there is a slight orange/brown tint, you may have some rust from the inlet screen or other plumbing. This tends to happen, particularly, after you have been making new connections.

Links

Someone else has a page describing how they fixed a problem with their ice maker. It has the same timer gear.

This may be the correct replacement solenoid valve

Approximate prices: Icemaker assembly $100 (not including solenoid), Solenoid valve $18, ejecter arm $10, timer assembly $70, thermostat $20.

More Info?

If this information helps you, that is great. If you want more information, DO NOT waste my time by asking. I am not in the appliance repair business. I have put a lot of information on the web on a lot of subjects and I don't have time for stupid questions or even questions that aren't stupid but which I am not paid $$$ to answer. The information I have is already posted here.