Refrigerator Repair: Not Cooling Part 2

Refrigerator Repair:  Not Cooling  Part 2.

“My fridge isn’t cold enough.  I think it needs a shot of ‘freon'”… I wish I had a nickel for every time I’ve heard that.

To be honest, there are some unscrupulous service techs out there who think a shot of “Freon” is a cure-all.  They’ll pump a little into the system either – not knowing what they are doing, or to make a few extra bucks.   They usually use a device called a “tap” valve to access the system.  They will leave these “tap” valves on, and the valves will eventually leak.  You will then need more than just a “shot of freon”.  (They are called tap valves because they tap into the sealed system by puncturing a hole in the tubing.)

As we said in the previous article – refrigerant is the least likely culprit to keep your unit from cooling properly.  When I was teaching refrigeration repair (or any appliance repair), I taught the students to first look for the obvious, not the difficult.

I’ve had techs go on a job and completely dismantle a multi-thousand dollar pizza oven just to find out that the breaker or gas was off.  Try explaining that to the customer.

So far, we have looked at:

1. The condenser coil

2. The condenser fan

3. The surroundings – air flow around the unit

4. The air flow inside the freezer… the vents

5. The gaskets or seals.

One thing I’d like to add about the air flow inside the unit.  In most refrigerator/freezer units you will find two controls in the fresh food section.  One will say something like, “Refrigerator temp” and the other may say something like, “Freezer temp”.  Only one of these controls actually is a t-stat, thermostat, or cold control.  The other one is just a “damper” that adjusts the amount of air that leaves or stays in the freezer compartment.

If you want the refrigerator section colder, you allow more refrigerated air to flow into that compartment.  If you want the ice maker to make more ice, you turn the damper so more refrigerated air stays in the freezer compartment and freezes the water in the ice maker – faster.

If your freezer is freezing and stuff in the refrigerator is growing hair, then check that damper.  You may have it closed.

The items that we are going to discuss have a tendency to be technical in nature.  Make sure that you, your uncle, or the kid next door has at least a slight mechanical aptitude.  One indication of a lack of mechanical aptitude is, if they approach the refrigerator with icepick and hammer in hand, or they start taking the thing apart without unplugging it first.

So, no matter who attempts these repairs, please make sure the unit is unplugged or that your home owner’s insurance is up to date.

Here’s the scenario.  The phone rings.  On the other end, I have Mrs. Hubby’s-a-geek saying that her fridge is not cooling enough.  “I think it needs a shot of freon, or something.  At least that’s what the kid next door said.”  She then goes on to tell me that she knows it’s working, “cause I can see the ice all over the back.”

That’s when I ask, “Is it snow-like ice, or ice-like ice?”   By asking questions, a good technician can practically have the problem diagnosed before he arrives.

If the freezer compartment shows snow-like build-up on the back (or bottom – depending on the position of the evaporator) there is a good possibility that you are having a defrost problem.  If it is solid ice-like ice, there is a good possibility that you have a drainage blockage in the evaporator compartment (that’s because you failed to clean the spilled baby lima beans from the compartment, etc.).

Taking for our example that you have snow-like ice in your unit, we will look at the three main components of the defrost system.  They are: the defrost timer, the defrost heater, the defrost terminator.  (Just a reminder, improper air flow can cause frost buildup.)

1.  The defrost timer.

This is the major cause of defrost problems.

There are two basic types of defrost timers.  One is the electronic type (printed circuit board) and the other is the mechanical type (looks like a motorized clock mechanism).  We will look at the mechanical type in this how-to article.

If you are lucky enough to still have your wiring diagram, you might be lucky enough to have one of those diagrams that gives a general location of where the defrost timer is.  If you do not, then finding this defrost timer can be difficult.

Most of the time the timer is located within the refrigerator compartment.  Look for a small button type cover about the size of a nickel.  If you pry this off and there is a slotted object behind that cover, then you have found the timer.  Sometimes the timer is located in the same compartment as the thermostat, and air flow damper.

I have found where some companies put the defrost timer inside the front leg/brace of the unit.  You can find these by removing the kick plate.

You will need the unit plugged in and on for this part of the diagnosis.  Once you find the mechanical defrost timer – slip a slotted screwdriver into the slot on the timer.  Slowly turn the timer a click at a time  (clockwise) until your unit turns off.  Once you hear the timer click and the compressor and fans cut off, listen for a slight hissing or popping sound in the area of the ice.  Give it a few seconds.  If you hear the hissing or popping sound, the defrost element is heating and the defrost terminator is at least in the closed (calling for defrost) position.  This would mean that the element and terminator are working.

Let the unit continue like this until the snow-like ice is melted.  Make sure the drip pan underneath is empty when you do this or you will have a mess on your hands when it overflows.  Usually a bad timer will not go back into the cooling mode until you turn the dial further, but on the rare chance that your timer starts working again and  the unit goes back into cooling mode in about 20 minutes, turn the timer again until it takes the fridge back into defrost.  Depending on the amount of frost, you may have to do this several times.   But replace the timer even if it does start working again.

Once the frost is gone, and the unit has not gone back into cooling mode, manually turn the dial one click at a time until the unit comes back on, then go or call your local parts distributor and give them the model and serial numbers of your fridge.  Do not remove the timer yet, because your unit will now begin to cool at least until you get the replacement part.  Tell them that you need the defrost timer.  Once you have the new part in hand, unplug your fridge and carefully remove the defective one and install the new.

This timer, unless your name is MacGyver, can not be fixed.  So replace it.

By the way, this timer can also cause your fridge or freezer to not cool at all, if it gets stuck in the defrost mode.

2. The defrost heater (element)

Defrost heaters come in several configurations.  The most common configurations are the “calrod”, quartz, or wire coil type.  The “calrod” looks like the element in the bottom of your oven.  The quartz is a smoky looking glass tube.  The wire coil heater is a bare wire coiled inside a glass tube which is sealed on both ends.  The “calrod” and the wire coil are the most widely used.

To access the heaters, remove all of the snowy frost by either carefully using a hairdryer, slowly pouring warm water over the ice (UNIT UNPLUGGED!), or just leaving the unit off and the door open, (You’ll need somewhere to cool your stuff while the unit defrosts naturally.) Do not allow the kid next door to get near the frost with his hammer and icepick!

These heaters will be attached to the evaporator in some manner and are located in the freezer compartment.  A word to the wise, if you attempt to check these elements in anyway….please have the unit unplugged and be very careful of the “fins” on the evaporator.  You can either bend them and restrict air flow, or you can cut your fingers off because they are very thin and very sharp.

Once you have accessed the defrost heater (on some models there are more than one heater) by removing the panels (you are on your own on that one, cause of the many models and variations on the market – just remember how it came apart!), you can visually check to see if there are any breaks in the heater itself or one of the wires.  If you do not see anything obvious, then go get that el-cheapo multi-meter that you purchased from Wal-Mart for about nine dollars.  Put the dial on resistance at the highest level, just to be sure(ohms).  The average resistance of a good element is about 20 to 50 ohms, but you’re more concerned with continuity.

After removing the leads from the ends of the elements (or from the wire nuts), place one probe on one end and the other probe on the other end.  If the pointer on the meter dial moves across the scale, then your element is good.  If it doesn’t, then the element is open (or the el-cheapo meter is broken) and it must be replaced.  Do this for each element.

When replacing the defrost heaters make sure  you put them back in the same place as the originals.  Make sure you save any brackets or clamps and put them in place where the originals were.  Also, it is wise to draw a picture of where you took each wire from.  This way you can reattach them where they are supposed to go.  And, if you take wire nuts off wire ends, seal them with a good silicone sealant such as the GE brand.

The elements can not be fixed.  They must be replaced.  Also, as much as possible, do not touch the new elements themselves with your fingers.  The oils from your fingers can cause hot spots and shorten the life of the heater.

3. The defrost terminator (snapdisc) (thermostat).

The defrost terminator’s purpose is to allow the defrost heater to come on, but not stay on so long that everything in the refrigerator thaws out.

It looks like a small disc or round object.  It usually has two wires coming from it (some commercial snapdiscs have more than two wires).  It is attached to the evaporator with the use of a spring clamp.

Its make-up is simple.  It is a thin metal disc inside a casing  that is temperature sensitive and snaps when the proper temperature is reached.  This snapping action causes the metal disc to open or close contacts by snapping on them or off them.  (Thus, the name, “Snapdisc”)

Here’s it operation.  When the evaporator temp is above a set temp (such as when first turned on), the defrost terminator is in the open mode.  (The circuit to the defrost heater is not complete.) When the temperature drops to the set closing temperature, the snapdisc inside the terminator snaps closed and completes the circuit to the defrost heater waiting for the defrost timer to go into defrost.

When the defrost timer reaches the time to take the system into defrost it sends current through the defrost terminator and through the defrost heater.  The heater gets hot.  Although the usual defrost time is about 20 minutes, the terminator will open and prevent current from reaching the defrost heater when the compartment and evaporator reaches the set “open” temperature.  This prevents the defrost heater from thawing out everything in the freezer and refrigerator compartments.

Checking this little feller can be somewhat hair pulling.  To get to it you have to remove the frost from the panels to remove them (the panels).  If you can do that without removing the frost from the evaporator, then you are good.

In other words, you have to check this device when it is cold enough to snap the contacts closed.  I use a can of chewing gum remover which freezes the gum in the carpet so it can be removed.  If you can get a can of this, spray the “contact” side (side that contacts the tube) while using your handy-dandy el cheapo multi-meter to check continuity across the wires of the terminator.  If the contacts are closed when it is frozen, the terminator is good.  if, when it is frozen, the contacts are open, it is bad.  If the thermostat does not reset once it gets below freezing, it is defective.

By the way, if the terminator contacts get welded closed through arcing, it can cause the defrost heater to stay on the entire time and therefore thaw out your goodies.

The defrost terminator can not be fixed.  It must be replaced and it must be placed in the same location as the original.

That is a simple break-down (no pun intended) of that part of the cooling system that causes the majority of the “not cooling” complaints.  When we meet again, I will discuss the evaporator fan and the thermostat (cold control).

Because each model of each brand is different, we can’t cover the locations of every unit, nor, can we cover the actual “getting too” the components.  That’s where a slight mechanical capability comes in handy.

Of course, there’s always the kid next door.