Evaporator Fan

Evaporator fans are located in the freezer compartment behind a metal or plastic bulkhead and pull air over the evaporator coil and circulate it throughout the unit. Almost all refrigerators have a damper assembly that controls the amount of air entering the fresh food compartment from the freezer. Normally this damper is manually adjusted, but on some models it is electronically controlled. Another complicated and unnecessary part for the factory authorized repair person to chuckle over when you pay a couple of hundred to replace it. The old knob and plastic damper solution worked as well and rarely had to be replaced.

 Evaporator Fan (2) pulls air over evaporator coil (1)

The evaporator fan is wired to run when the compressor is running. If the evaporator fan fails the compressor will run longer since there will be no air flow to the fresh food compartment where most cold control sensing bulbs are located. The temperature will go up in the fresh food compartment and the evaporator coil will ice up causing the freezer temperature to rise.

Sometimes a defrost problem will ice up the evaporator and jam the fan blades. Before assuming the evaporator fan is bad, disconnect power, remove cover from fan and evaporator coil, and ensure that blade is free to turn. With power off, disconnect the wires from fan motor and read windings with volt-ohm meter. A reading of infinity indicates an open motor winding and the motor should be replaced.

If the fan blades are impossible or difficult to turn suspect a seized bearing. An evaporator fan with bad bearings occasionally emit a high-pitched squealing noise that is impossible to ignore.  

Cold Controls

The refrigerator cold control or thermostat is an electro-mechanical component that controls the starting/stopping of the compressor and is one of (usually) two adjustable controls that effect the temperature inside the refrigerator. The other is a damper valve to adjust the airflow between the freezer section and refrigerator section. Both these controls are usually knobs with numbers or letters and it is sometimes difficult at first glance to determine which is a mechanical valve and which is an electrical switch. The cold control has an off position that turns off power to compressor. Both controls usually have a default or mid-range position marked on their numbered scales. In a properly operating system setting these two controls to midrange should result in acceptable temperatures in the freezer and refrigerator section. If it does not there is likely a problem.

 

 

Cold Control (a pressure actuated switch)

 

The cold control has two wires. A hot lead that is usually energized as soon as the refrigerator is connected to an outlet and a switched lead that is hot when the  pressure against a bellows pushes the contacts to the closed or made position. The compressor then starts and runs until the colder temperature reduces the pressure and the bellows opens the contacts. The pressure is derived from refrigerant inside a sealed capillary tube and bulb assembly attached to cold control body. If the cap tube is damaged and the refrigerant escapes, the cold control will no longer make to provide power to compressor. In this case, the compressor may be judged bad when the problem is a defective control. If the cold control sticks in the closed position and the compressor runs constantly, the evaporator may eventually ice over and look like a defrost problem.

Schematic:

 

Note that the temperature control (cold control) receives power from line side of cord. If the control is made power is fed to the defrost control. The defrost control sends voltage to the compressor start circuit, evaporator fan, and condenser fan. When the defrost timer calls for defrost the compressor and fans stop and power is sent to the defrost heater circuit. Obviously an open cold control will keep the compressor and fans from running. The easiest way to test is to unplug refrigerator, remove the cold control so that the two wires can be disconnected and take a reading across the terminals with a volt-ohm meter. If the refrigerator is above set point and the cold control reads infinity the control is bad. A control with shorted contacts will cause the refrigerator to run continuously except when the defrost timer switches to a defrost cycle.

Most New Refrigerators Are Crap

After working at the appliance recycle center (used appliance store) for a few years, I started volunteering to repair appliances at a Habitat For Humanity Resale Store. People would donate used appliances to be refurbished and sold to raise money to help fund building houses for poor people (not so poor that they couldn’t afford the mortgage payments however, which meant that real homeless people couldn’t qualify). In addition to donations of appliances from the general public, the store received appliances from a nationwide retailer of appliances. When a customer bought a new appliance from the retailer and wanted the old one removed, it was donated to Habitat. Appliances that were returned to the retailer as defective were also donated (as a tax write-off). Thus I was in a position for three years to observe the defects that made people purchase new refrigerators and to see the brands with the most factory defects.

In fairness to appliance manufacturers, I should point out that many of the new appliances returned as defective worked perfectly. Either the buyer changed his or her mind and wanted a refund and made up problems or couldn’t recognize a refrigerator that was working properly. Over the three year period at Habitat, I saw at least fifty of these used three-days returns even though nothing was wrong sell for approximately half-price (if they weren’t diverted to the relatives of the store manager who had paid positions in the store). Discounting the phoney returns it was still obvious after a few months that Frigidare had more factory defects than other brands. GE gave Frigidare a run, but couldn’t quite match them for shoddy construction. Even though these two brands accounted for most new defective appliances donated to Habitat doesn’t mean they were the worst built. Obviously, they were being sold more than other brands exposing more factory defects than brands with less market share. The worst built refrigerator in my opinion was Haier, a Chinese company who has a goal of 10% market-share in the US and tried to buy Maytag in 2005. That damn Maytag repairman would have had plenty to do then. I expect that throw away plastic refrigerator I predicted in the last post to be produced by Haier. On the other hand, why should Haier produce a better refrigerator than necessary to compete with the low-quality units with more familiar names.

Quality will continue to decline as long as consumers are willing to accept cheap and shoddy.      

When All Else Fails Blame The Compressor

Perhaps as refrigerator manufacturers continue the trend to build their products more and more shoddily and cheaply, compressors will become as prone to failure as incompetent repairmen would have us believe. For years the hermetic compressor was so well made and reliable that it wasn’t uncommon to find Frigidaire refrigerators from the 1950s still working. GE made compressors in the 1970s that were so reliable and long lasting that they are still working today. The only reason they were replaced was because those lovely chassis colors (gold, green, and brown) went out of style and were replaced by almond, white, and black. Those old horseshoe compressors were made to last at least twenty years and many are working thirty years later. Don’t get me wrong, in the 21st century GE and Frigidaire are producing the same kind of throw-away, get it through the warranty, crap that most appliance manufacturers are making. Quality and longevity have plummeted leaving only the cost high. The average life of a refrigerator has dropped from twenty plus years to eight years and keeps going down. This is intentional and will continue as long as there is a profit in selling crap.

I sometimes wonder if the switch from R-12 to R-134 in the 90s wasn’t more about getting rid of the old, reliable refrigerators in the world and selling throw-away crap than concern for the ozone layer or environment. When R-12 was phased out of production and the cost of that refrigerant went to nearly a thousand dollars for a thirty pound tank, no one repaired pre-1995 refrigerators if there was a freon problem or if the compressor was bad. People bought one of the environmentally friendly models using R-134 (even though they are being hauled to landfills at a much higher rate than old bad refrigerators). If current trends continue, I envision (sooner rather than later) an almost all plastic refrigerator weighing forty pounds with no serviceable parts, costing two hundred dollars, that will be thrown away when it fails (and the failure date will likely be preprogrammed into a control chip).

Okay, enough soap-boxing. For the moment refrigerators may suffer from low-quality, but they are still repairable and this post is about compressors.

A new hermetic compressor.

Compressors are vapor pumps. They pump refrigerant gas from the evaporator coil through the suction line into the high side condenser (where it cools and condenses into a liquid). Only the circulation of refrigerant removes heat from inside the refrigerator. The compressor is started and stopped by the thermostat (cold-control) through a starting circuit. This normal start/stop cycle is interrupted during defrost cycles if the unit has automatic defrost.

Most refrigerator problems are caused by electrical problems in the circuits that control the starting of the compressor or automatic defrost and not by the compressor or freon charge.

Typical location of compressor (G)

This blog will not cover the replacement of a compressor since it is beyond the scope of the average homeowner. The job requires removing refrigerant which requires special equipment and an EPA certification.

Condenser Fan

Symptoms similar to a dirty condenser will be experienced if the condenser fan does not operate with a forced air condenser. Temperatures in the refrigerator section will likely rise into the fifties and the temperature in the freezer section will be in the thirties. Since the unit cannot cool to the set point of the thermostat (also called the cold control), the refrigerator will run constantly. Condenser fans are located at the rear of the refrigerator at the bottom behind a removable panel.

Refrigerator with back panel removed.

 

The condenser fan can stop if the motor is defective, but the fan blades can become so clogged with dirt and debris that they cannot turn even though the motor is good. Loose or broken wires can interrupt power to the motor. Bearings can seize and prevent the motor from turning. Do not work on live circuits or place your hands near the blades of the fan.  I have seen many condenser fans that had stopped turning due to debris that would unexpectedly start again. Unplug the unit before checking freedom of rotation, inspecting for dirt, debris, and foreign objects jamming blades or cleaning. With power off, inspect the wires supplying power for loose connections or damage to wiring. The condenser fan motor is 120 vac and is wired to run whenever the compressor is running.

 

General location of condenser fan (F)