My fridge, after working for about 20 years, stopped some time in the night. By morning the contents of the freezer were half-thawed. I pulled the fridge out of its niche and unplugged it (plug is inaccessible otherwise.) I ascertained that the power is reaching it - the inside light worked - but otherwise it was dead. I transferred all the contents to another fridge in the garage. Leaving it plugged in to another socket I went to look up fridge repairers and fridge sellers. Unable to contact a repairman, I went back to the fridge and found it running. It is still running 24h later.
I am hesitant to put it back in its place and return all the contents, because not knowing why it stopped makes me think it might happen again. Somebody in this group might be able to explain what causes a fridge to stop then start again, and let me know if there is a way to fix this or is the fridge on the skids.
If it does, we had one which kept doing this and it took several visits ( under warranty) to get it fixed.
It turned out to be the defrost timer. On ours, this was an electro mechanical beast, smaller than a match box. A small knob was visible in the fridge which rotated although we were never aware of it until it was pointed out. The faulty one stopped when it felt like it, in our case leaving the auto defrost heater on. It started sometimes but it was obvious the freezer had failed. The company, Whirlpool, took several attempts to fix it and replaced several freezer loads of food. They also gave us another 5 year warranty for free. We gave the fridge freezer away, still working, about 20 years later.
It is Frost Free, so I guess it must have an auto defrost function, and a defrost timer, and your suggestion sounds very plausible. Where should I look for this device? What electrics the fridge has are not at all visible or accessible, as far as I can see. Because it is old the Westinghouse site doesn't seem to recognise the model code, otherwise I'd get the manual and find out where the timer is located.
Thanks, another useful suggestion. I did try fiddling with the temp control knobs, but with no apparent result. I guess there must be two thermostats, one in the fridge and one in the freezer - is that right? I have posted an inquiry with a local appliance repair outfit, it looks as if somebody with expert knowledge needs to come to debug it. Meanwhile we'll keep using the fridge in the garage.
In a typical upright refrigerator, with a freezer section and a milk/produce section, the bottom part (milk/produce) is regulated, while the freezer section "free wheels". The freezer section does not "call for cooling". There is no control for it.
The thermostat is one of two types, and sits in the milk/produce section. One of the types, is absorption type, and there is a sealed refrigerant gas inside the sensing tube. And that has something to do with temperature sensing. It's not a bimetallic strip or anything easy like that.
The bottom part of the fridge is a bang-bang controller, just like your heating system. Say the target temperature for milk is 1C or 2C or so. When the temperature rises above the threshold, the sensor detects that, and a relay is used to start the compressor. The sensor does not run the motor directly, as that would be hard on the switching element. The signal to commence, is "amplified" with some sort of starter relay.
You have one knob in the lower part of the fridge, that sets the trigger point for milk/produce cooling.
In the freezer section, there is one fan and two airflow paths. A knob entitled "ice cream hard" or similar, adjusts the airflow in the two sections of the fridge. To make "ice cream hard", most of the airflow goes to the freezer compartment, very little airflow goes to the bottom compartment. With very little airflow to the bottom compartment, the compressor runs for a long time to reach the milk/produce target temperature. The milk/produce thermostat, tells the compressor when to switch off.
In the meantime, the upper compartment has hit -18C or so, because it's getting close to the temperature of the aluminium heatsink next to the circulation fan.
If you adjust the knob for "ice cream soft", then more of the air is deflected to the lower compartment. Now, it only takes five minutes for the lower compartment to hit 2C. The upper compartment might only be -10C at that time. The ice cream will be softer.
That's what I mean by "free wheeling". The upper temperature is only approximate. It might be -10C one day, and -12C the next day. The bottom compartment has less variation in temperature. The top compartment is generously cooled, so the food won't spoil over the range of -10C to -12C. Normally, you'd adjust the airflow for a bit lower than that. I used -10C as an example of someone who insists on soft ice cream, even if other foods suffer.
When you get a new "old fridge", you calibrate by first setting the lower compartment temperature with a thermometer. Adjust up or down, until maybe six hours later, you seem to have reached the desired target. Then put the thermometer in the ice box, and monitor the upper compartment, as you adjust the upper compartment airflow. This sets the free wheeling behavior in the rough range you want. Again, you have to wait large amounts of time, to see what temp it achieves. The upper compartment has no mechanism to "snap to attention", and it takes a long time to reach steady state.
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The defrost timer is a tiny shaded pole motor, with gears and a cam. The cam is used to work a switch. The switch is a bastard, with heavy contacts. This stresses the cam and wears on stuff. That's why defrost timers make funny noises, when they're worn out. There is mechanical damage to the defrost timer. A lighter switch contact, would have meant a longer life.
The defrost timers have a time constant, which does not divide evenly into 24 hours. It might be a 10 hour timer. This causes the defrost interval, to "walk around the clock" from day to day. So it does not align in unfortunate ways, with the way people work. Not all defrost timers have the same time constant.
The defrost uses a heater. There is a defrost thermostat, whereby, if there is little frost buildup on the aluminium heatsink, the defrost cycle is short cycled. If there is a lot of frost, it takes a while before the heat sink climbs over 0C and the metal is frost free. The overall defrost cycle also has a max_time, so the heater won't stay on forever. The defrost time could be five to fifteen minutes maybe. Once the defrost timer switch returns to the "normal" position, the milk/produce thermostat says to "turn on, we need cooling". The lower thermostat is only honored, when the machine is in "normal" mode.
There are a few modern refrigerators, with a processor inside, two fans, a variable speed compressor and an "analog" control loop. Gone is the bang-bang control method. Consequently, the above description no longer applies to everything. Only the old reliable ones. According to the salesman I talked to, he thinks the new ones will last ten years. Whereas the old ones, could last 40-50 years (and about three defrost timers, a new fan, a new thermostat). The one I replaced, was suffering from structural rust in places. Once moisture gets into parts of the thing it does not belong, it's all downhill from there. The newer refrigerators use solid foam insulators, which changes the insulation degradation properties somewhat. But nothing lasts forever. Since they still use steel, rust is inevitable.
Hi Paul, thanks for all that detailed info - a lot to digest here. My fridge is apparently a bit different but no doubt the same basic principles apply. It is an upright with the freezer at the bottom. In the milk/produce compartment there are two temperature control knobs, one for that compartment and one for the freezer. There is no icebox as such, but the top right corner is particularly cold - that's where the cold air enters the compartment. It seems clear that the knobs somehow control how the cold air flow is shared by the two compartments. Presumably the defrost timer (a likely guilty party) is located in the back at the bottom, near the compressor. It's hard to see how anything can be accessed for maintenance, but there must be a way.
I have now discovered that access to the working parts (except the compressor) is inside the freezer. I removed the cover over the cooler, and took a picture - but I don't know how to send a pic here.
After upload, copy the "Direct Link", the whole thing.
Using a second browser (upload with Firefox, verify in Chrome), load the Direct Link into the second browser and verify the image is visible and is not too fuzzy. There is a tab at the top of the viewing pane that supports "direct download", which presents the recipient a better quality image they can access.
For your first try, keep the name short to make this easier, like "pic.jpg" maybe.
There are other free image upload sites.
By the way, that site uses $30,000 per month of download bandwidth, by people viewing the pictures. Just to show how bad of an idea it is, to run an image sharing site :-) It takes a lot of advertising, to cover that tab.
The site was closed once by the US Government, requiring a domain change to go back online again.
One of the things I struggle with, and this has been mentioned in another thread is that my Fridgemaster has no drain in the lower section, ie produce part. This means seemingly that when it does a defrost it tends to end up with water in the bottom of the fridge. Since it is not doing it all the time, one assumes there is a mechanism to somehow mop this up internally before it gets to the bottom, and it looks to me like it is either forming on the back of the fridge, the cold plate behind the bottom shelf or leaking down the air vent from the freezer. The back is covered in so having a look at the pipework is really out of it for now. There is one neoprene pip seen on one corner of the evaporation tray which you can see at the bottom of the back over the motor area. However very seldom do I see any water come out of it, but the freezer does defrost, so its rather obvious where its nearly always going!
In the motor department, there are clearly at least two. One operating the compressor, and one operating a fan, and the latter seems to be controlled separately to the compressor, and has also started to develop a squeak from time to time and you can feel its draft both inside the freezer where there are vents at the back, and on a couple of holes near the top of the fridge where air not quite as cold comes in and out of it. Nearby this in the produce department is the thermostat knob which as you say sounds like its just an ordinary thermostat that clicks over as its turned. Not exactly sophisticated. So where is this ally plate you describe? One assumes it has to be somewhere near the fan and condensation forms there and is piped away during defrost. I assume its behind the grill in the top compartment? The only control in the freezer is a kind of sliding plastic piece that is very easy to knock and controls the airflow, ie it has no real control other than by making the air go more in one direction or another as far as I can see. The design is also a bit annoying as if you shut the freezer door with, say a loaf laid down, that gets pushed back and blocks some of the airflow as well, but you only find out when you open it.
My duff fridge is in the carport at the moment, easy to inspect.
The drain hose comes out the back of the chassis, from the drain area of the defroster. The hose travels outside the chassis, so warm room air avoids the material freezing and plugging the hose. The hose travels down the back of the fridge, then darts back in via the compressor bay, to the drain tray which is close to the floor and is about the same size as the width times depth of the fridge.
Normally, drain trays are arranged to be near a heat source, and some of the heat-dissipating pipes of that fridge, are near the drain tray and they help dry the water. The new fridge uses the heat of the compressor, to dry the water.
The drain hose diameter is 1/2" or 5/8" and the large diameter is necessary for when mold, mildew or other biologicals try and block the pipe. Otherwise, a 1/4" tube would be sufficient for the flow, but would plug up in months.
If the hose were to plug, the water is going to go somewhere.
I've seen another design, where the water coming from the defrost of the freezer section, flows down the back of the refrigerator compartment (inside!) and collects underneath the produce drawer. And there is a drain hole in the bottom of the fridge. The concept there is, the produce section should not be freezing, so the water that collects down there should drain OK. That's the fridge that also makes a mess on the floor (water doesn't evaporate fast enough from drain tray, drain tray overflows).
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The ally plate has fins on it, so is shaped like a heatsink. It is located in back of the freezer box, and the fan is located right next to it. There are also designs, where the ally plate is underneath the freezer box and has a horizontal orientation. Usually, there is a tin foil cover over some part of the gadget, and you hear a "spitting noise" during defrost, as the heater element can boil droplets of water that fall on it. When doing maintenance, you must put that foil back. It doesn't take long before that foil looks terrible, from the handling it has received.
You cannot touch the ally plate, without removing the covering on the inside back of the freezer box. This is tricky. Sure, there are four screws that hold the cover in the back. But there can be fittings that prevent the plate from rotating out of place. The "trick" in this case, is the cover on the back of the freezer box, has a loose fitting rubber gasket around it. Using a flat blade screwdriver, you depress the rubber gasket with the blade of the screwdriver, and like magic, the plate "just barely clears" the fittings on the side of the ice box. It takes some amount of playing, to get the thing to come completely out of the fridge box. Now, the ally plate is exposed.
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Note that the circulation fan you describe, it can have bronze bearings. There is a warning label next to the fan that says "Do Not Oil". It is a permanent bearing and does not use oil. Hearing a squeak is a bad sign. A steel shaft on a bronze or brass bearing should not squeak. It's true that you can keep the thing alive, by oiling it for six months, but sooner or later, you'll be sorry, I assure you. I don't recommend oiling it, unless the RPMs have dropped to half the normal value.
The fan is just a shaded pole motor, maybe 6W or so, which runs cool to the touch. After all, it cannot dissipate too much power, as this eats into the efficiency of the refrigerator. It has to be a very low power device. And a shaded pole motor is a poor choice from that perspective. But a better motor, might not last for forty years. When I finally got my hands on the shaded pole, the bearings were covered in rust particulate. As if the magnetism was attracting the stuff. I did not do a complete post-mortem on the fan, as I was in no mood for it at the time. The designs are simple enough, it's possible a "generic" solution might fit where the old one was located. (A number of the replacements look similar to one another, but the design of how the fan attaches to the shaft can vary.)
Before going to the part shop, always take the model number with you, so they can cross-reference and find an equivalent. At the recycler (where I shop), I just take the part in and they sort through the bin for one. That's how I got my defrost timers. The first was a dud, not lasting all that long, but the second one was a champ. Even though it was making worrisome noises, the noises eventually settled down. I'd bought a third, expecting trouble, and the third remains unused. I'd take it back to the recycler and have them throw it back in the bin, but they're out of business.
I wouldn't buy a thermostat there :-) I want something a bit more reliable than a recycled one for that. The recycler had both new parts and recycled ones, and if a cross reference didn't find a new one, that's when (with your permission) they will go look in the bin. That's how the fridge lasted as long as it did. If I went with new parts, I would never have got the parts needed. Having a backup supply of junk, is very handy.
One of the reasons the business climate here has changed, is funding for recycling has changed. And recycling a fridge, the scrap value is not nearly enough to pay the bills. The end result of this, is nobody wants your old fridge any more. You used to get disposal for free here, even if the people doing the pickup were "slow-pokes". That's why the fridge is in my carport. Grrr.
Next project, is to build a catapult, to launch the fridge into space.
Now, that's like the "back view" of mine, the view I would not have access to.
Yours seems to have a reverse orientation to how mine was set up.
The wiring jobs they do in these, give me the creeps.
Is that green wire connected on the right ?
Mine had push-on connectors for the fan, but much of the wiring was loose like yours.
I would expect to see some sort of defrost wiring, as well as a defrost thermostat (overtemp switch).
I see what looks like a piece of foam on the upper left, and mine has that too. Random pieces of foam used to hold the wires in place, or space something. But it all lacks a sincere effort to do a good job.
If there is a defrost thermostat, mine was a cylinder about 3/4" diameter, maybe 5/8" tall. And resembles the same form factor as the overtemp switch in a kettle (near the base plate). So it's probably not a thermostat, the one on mine. But there was some deal about the defrost cycle being "truncated", once the aluminium gets warm enough. The idea is to not allow it to get so hot, it melts the plastic in the area. The foil covering is presumably part of the safety for the thing. Yours doesn't seem to have a reason to use a foil, by the looks of it.
Looking at that, my guess is your fridge is no different than mine, in having only one control loop. And the ice box only has control over defrost in evidence, rather than anything that controls a "call for cooling".
The sensor in the bottom section of the fridge, the "milk section", there should be a small diameter copper tube leading from the rotary control knob. I couldn't figure out exactly how that worked, or why it remains tight and leak free for decades. I also couldn't figure out how to get mine apart. I got the cover half off, but it would not come all the way off. And if you break it and you can't get the part... game over :-)
The new fridge, I thought it was going to be "too small", but as it turns out, the new fridge dumps the heat
*out the sides*, and the extra clearance to the walls actually helps. It's like I planned it that way :-) I didn't even think of asking, as I assumed the heat would be dumped out the back. I was wrong.
Hi Paul, The green wire is just the earthing wire that was connected to the cover, which I removed. On the left side, about halfway down, there is a small white cylindrical object with two wires attached. It isn't easy to see in the pic. I suspect this might be a temperature sensor/thermostat. I am still puzzled about how the auto-defrost functions. On the the right hand side there is an important-looking long cylindrical thing wrapped with brown plastic. Could that be related to the defrosting? Hang-on! Perhaps I am wrongly thinking about defrosting. The fridge calls itself Frost Free, and I see on the door a sticker that claims "No defrosting of either Refrigerator or Freezer". So perhaps I shouldn't expect to find a timer or switch controlling defrosting. Then how does it work? It definitely does work - there is never frost in the freezer. Maybe this is related to your recent comments, which I do not fully understand.
I have to correct myself. At the back, next to the compressor, behind a galvanised steel bracket, I find a 6h timer. This is an obvious candidate for the cause of the problem. If it was switching the heating plate on then either leaving it on or not restoring power to the compressor after a short time that would result in a general melt-down. The remaining uncertainty I have is: when does the heating stop? Is there a signal that indicates when all the ice has been melted? If so, the problem could lie there rather than in the timer. I guess the other possibility is a thermostat problem.
To add to this, I have found a couple of suppliers of the timer, and it is sometimes referred to as "6/21", meaning 6h as the cycle time, 21 min as the heating time. This suggests, but doesn't prove, that there is a fixed heating time. However, the unit has a knob on it, which obviously controls one of the times. My timer doesn't say anything about 21 on it, it is like this one, but black not white:
Paul, thanks to your detailed explanation I now have an almost complete understanding of the control system. The only point at which I remain uncertain is my failure to locate a thermostat in the milk compartment. The device on the cooling fins is clearly the thermostat to limit the defrost heating, but where is the one that controls the normal bang-bang compressor operation? I am wondering what failure of the heater thermostat would cause - my guess is that it would not prevent the return to normal operation. This leaves misfunction of the other thermostat as a possible cause of the melt-down, after the defrost timer, which seems the most likely candidate. The repairman has replied by email, saying he charges $90 to visit, then $15/10min thereafter. I can see that I could pay $180 + the timer cost for a job that I could do myself for just the cost of the timer ($40, I think). By the way I'm in NZ. So I am considering just buying timer and replacing it myself, but wondering if I should also replace the thermostat, location unknown.
A tip, when ours failed it destroyed the heater at least once.
As I recall (and it was 30 years ago +/-) they disconnected the heater and timer so we could use the fridge freezer while they got parts. It didn?t frost up in the few days etc.
It took them several attempts to fix the problem. The timer was one of the last things they changed.
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