Tuesday, September 1, 2015

DIY Refrigerator Repair. Now 20% Easier!


Refrigerator graveyardIf you are a homebrewer, you probably have or will have an investment in refrigerators or freezers. Prior to this article, I had a chest freezer that I had converted into a "Keezer", which, for those unfamiliar, is the combination of the words freezer and kegerator. It was a 15 cubic foot Frigidaire chest freezer I purchased brand new and installed a Johnson A419 Controller which kept the freezer from freezing, but at a nice 36 degrees F.  Large enough to store 8 Corny kegs with CO2 plumbed into the lid to pressurize and serve. Then one day, it died.  It had served me well for over 5 years, but living in the harsh environment of the garage and during a 6 week heat wave with temperatures in the high 90's (F.) and humidity around 85% relative, it decided that it had enough.

Vapor Compression RefrigerationRefrigerators are reasonably simple machines that are only made complicated by modernization that add in-door ice dispensers and multiple temperature zones. Our home refrigerator has features like "power cool" and "rapid freeze". I have no idea how these are intended to work, but the basics of the refrigeration device are simple. Most refrigerators, your home and automobile air conditioner all work on this same "Vapor-Compression cycle".

Refrigerator airflow diagramA compressor pressurizes a refrigerant (usually Freon) and as it does so it generates heat. The "coils" on the back or bottom of the refrigerator allow most of the heat to dissipate through the use of a fan that blows air (outside the refrigerator) across them.  The refrigerant should become a liquid at this point before it is then allowed to expand through a "throttling valve" or expansion valve. The refrigerant then rapidly cools through the Joule-Thompson effect where it is then sent through the evaporator (inside the refrigerator).  All cooling work is done inside the freezer compartment of the unit and the refrigerator side is kept cool through air management.  Since I am working with "Craig's List specials", these are older, much simpler refrigerators that are easy to take apart and work on.

One caveat before continuing. The refrigerant circuit is a closed system and Freon is considered a hazardous material. You should not attempt repairs on the closed system unless you have the proper tools, training and licenses.  The issues I have fixed did not involve the replacement or repair of any of the closed system components.

Onto my specific problems with my refrigerators.  The first problem I was having was that the freezer was attaining temperatures less than 0 (zero) degrees F., but the refrigerator was approaching 60 F. As shown in the image above the air from the freezer is pumped into the refrigerator cabinet by using a fan and some baffles.  First some troubleshooting.  UNPLUG the refrigerator first!  Inside the refrigerator cabinet is the main control unit.  Given that this was an older refrigerator, there were no circuit boards to contend with, just some elctro-mechanical hardware.

Remove the screws (these were Phillips head) and unplug the main harness so the components can be tested on a bench. Way back in the before-time, folks had to manually defrost the refrigerator by unplugging it and chipping the frost away of waiting for it to all melt.  More modern units (and these are still dinosaurs) have automatic defrost cycles built in so that moisture in the air doesn't accumulate on the evaporator and cause it to "freeze up".  This particular refrigerator uses a timer that starts the defrost heating element after every 8 hours of operating time.  That's not every 8 hours you have it plugged in, but 8 hours that the compressor is running.  If you don't have ice all over the evaporator coils, I would assume that this circuit is working and focus on something else.
Refrigerator main control unit
I didn't take photos of it, but by using a volt meter on the continuity setting (it beeps when the circuit is closed), I tested the temperature sensor by removing the two spade lugs connected to it, connecting my volt meter across the two connectors and placed the metal probe in a glass of ice water. Turning the adjustment knob back and forth, the meter would beep when the circuit closed (this would turn the compressor on because the refrigerator was too warm) and not beep when the circuit was open (this would turn the compressor off because you had reached the desired temperature).  For reference, these older defrost timers have a manual advance that can be rotated with a flat-head screwdriver to test the heating element and sensor if you need to. I didn't have that problem, so I didn't run that test. Other than replacing the door switch so the interior light would come on, this all checked out.  The next thing to look at was the evaporator and airflow assembly in the freezer.

This is what is behind the metal plate in the back of the freezer.
Another use for duct tapeAs you can see the evaporator is not frozen up, the air supply and return vents are not blocked so there is only one thing that can be wrong with this unit.  The fan is working, but not supplying the correct amount of air needed to cool the refrigerator.  I used Appliance Parts Pros to find the parts for my refrigerators.  You put in the model number you are working on and they have exploded view diagrams with all the parts referenced.  I ordered a new fan motor and blade along with the door switch. While I was waiting for my parts to arrive, I taped over most of the vents in the freezer forcing more air into the refrigerator cabinet. This confirmed my troubleshooting as the temperature in the refrigerator began to plummet to more reasonable temperatures.  Another use for duct tape.  After 24 hours the refrigerator began cycling on and off as the temperature reached the setting the sensor had been set to.  Before the "duct tape" the compressor had been running for 36 hours straight without getting the refrigerator to temperatures below 50 (F).

When the parts arrived from Appliance Parts Pros, it took me less than 30 minutes to replace both of them.  The refrigerator is now behaving as one would expect. The unit with the bad fan was purchased 2 years ago and just started behaving badly, someone didn't sell it to me that way.  I was suddenly asking a lot more of it once I stacked it with 4-5 gallon Cornys' and wanted them all just above freezing.  
I did attempt to fix the chest freezer, but that has no air management and no defrost circuit.  The compressor was running fine, but the cabinet would only get to 40 degrees (F), so I sold it to the appliance repair shop.  It either was low on Freon (which means it leaked somewhere. Not good) or the gas filter was clogged.  Replacing a gas filter requires removing all the Freon, soldering the lines apart and back together, vacuuming out the Freon circuit and replacing the Freon.  All way beyond my capabilities and equipment budget.  The motor and switch cost around $60 with a new fan blade, which is about what I paid for the refrigerator a couple of years ago.  But 1) I didn't have to move any of my stuff, 2) I didn't have to haul a new/old appliance around and 3) I didn't have to redo all the CO2 plumbing I had just finished.

I really had no idea that this was a thing and was clueless to the whole "bronyism" and "bronyspeak" subculture. I was just looking for a "cooler" internet meme to add to my conclusion.  

Want to "ponify" your browser so that you can read like everypony instead of everybody? You can do that, watch the video linked above.  I think I hurt my spleen laughing so hard. Just search for "Ponify".  I spent way too much time reading about this, since I thought it was a joke and I kept waiting for the punch line.  Awww, yeah!

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