Scholar of Advanced Appliantological Studies
|Joined: ||Wed May 3rd, 2006|
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|Flavorite Brew: ||Homemade wine|
|If it is an older model check this out, if this is your problem you can still purchase the repair kit for $30 or $40 bucks.
Repairing the Harvest Thermostat Solder Attachment
The older design of this machine used electromechanical controls, including a harvest thermostat on the evaporator plate that clicks on and off with the ice slab temperature. If your machine uses the newer electronic controls, you will have an electronic thermistor on the evaporator instead of electromechanical thermostat, and this section does not apply.
The evaporator plate in the top area of the ice machine circulates the hermetically sealed refrigerant (R-134a lately, or R-12 in very old machines), which boils off to carry away heat from the waterfall passing over the plate, resulting in a layer of ice being progressively built up. The top of the evaporator plate, where the ice forms, is smooth. The bottom is a complex affair containing the refrigerant line connections, and a bracket and clamp holding a capillary tube from the harvest thermostat. A complete assembly (327505 evaporator $266.02) is the only replacement part available from Whirlpool, but the old part can likely be repaired.
To diagnose the problem, it helps to understand the principles on which the machine makes ice. The running machine is always in one of two modes, either ice-making (chilling the plate) or harvesting (warming the plate). The capillary tube senses the temperature of the evaporator plate, which triggers two control events in the machine, depending on what the state of the machine is, and on the temperature reaching a level well-below or well-above freezing:
The bracket and clamp holding the capillary tube are about 1" wide by 4" long. The bracket itself is soldered to the bottom front of the evaporator plate, and a smaller clamping plate is held by a screw post and nut to the bracket. This creates a solid thermal connection between the capillary tube and the bottom of the evaporator plate; inside the tube, a liquid expands and contracts with the sensed temperature. The tube transmits this expansion/contraction pressure to the thickness control thermostat at the front panel, where the pressure triggers the switch that controls the cut-out and cut-in of chilling versus harvesting.
- In the ice-making state, when the evaporator plate temperature drops below a sub-freezing setpoint (set by the front-panel ice-thickness control), the unit switches to the harvesting state, reversing the refrigeration and thus heating the plate so that the ice slab thaws slightly and slides off onto the cutter. During harvesting, the water valve opens to refill the recirculating reservoir and flush the "used" water out via an overflow drain, while the recirculation pump stops. (The freezing process removes minerals from the water in the deposited ice, and concentrates them in the "used" reservoir water, necessitating a flush lest the minerals concentrate in the reservoir.)
- In the harvesting state, when the evaporator plate temperature rises above an above-freezing setpoint (the ice slab has slid off the plate, and the reversed refrigeration continues to heat the plate), the harvest state is ended and the unit switches to ice-making again. The water fill valve closes, the recirculation pump starts, and the refrigeration unit switches back to chilling the plate.
A few inches of the capillary tube should also be soldered to the bottom front lip of the evaporator plate. This helps it to quickly sense the rising temperature during the harvest cycle, which should end as soon as the ice slides off.
The failure of the bracket solder joint occurs because of the repeated cycling of sub-freezing chilling to make ice versus above-freezing thawing to harvest the ice. The area is always wet, and the solder joint will typically have small pockets or bubbles, which when wet will freeze and become slightly larger due to the expansion of the ice. Each freeze-thaw cycle enlarges the flaw slightly, and eventually this grows into a large fracture, just like fracturing of mountain stone from years of winter/summer cycles.
If you suspect you have the problem of the fractured solder joint, you can inspect the joint by removing the cutter grid and reservoir bucket. You can recognize the bracket, since it is the only item in the vicinity having a screw post and nut. If the solder joint does not appear intact along the entire length, but appears cracked or slightly separated, then you have this problem, but perhaps not very badly (yet). If the joint is mostly cracked, such that you can wiggle the bracket; or if the bracket is completely loose from the plate and is being held only by the capillary tube, then you have a definite problem needing repair.
The bracket is hard to view directly without pulling out the evaporator plate, which is a big job. You should be able to blindly feel around to the front or back of the bracket, nudge it with your fingers, and find it moving relative to the evaporator plate. Indeed, if the solder joints have almost completely failed, the bracket can fall right off with this manipulation.
Last edited on Tue Nov 2nd, 2010 03:59 am by fixit guy