12 cu ft frost free fridge not cooling properly

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I have a 12 cubic foot frost free fridge (Camco Model CRT1200VLT-1) whose freezer isn't cold enough to keep meat frozen. This is one of those GE apartment size fridges where you have to take out the freezer floor to get to the evaporator, evaporator fan, defrost heater and defrost thermostat.
I can feel a draft in the freezer compartment, so I know the evaporator fan is running. On this fridge the defrost thermostat diverts power from the cold control to the defrost heater, so if the evaporator fan is running, then the cold control is calling for cold, the evaporator fan and compressor are getting power and therefore the fridge can't be stuck in defrost mode. The compressor sounds like it's running when I use a mechanic's stethoscope on it and the line between the compressor and the condesnor coil behind the fridge is hot to the touch. Still the freezer compartment isn't getting cold enough to freeze water or keep meat frozen.
I replaced the cold control, but that didn't do any good.
Until now, this fridge would make a loud knocking sound when the compressor stopped, presumably due to a broken suspension spring inside the compressor housing. Now, the compressor and evaporator fan seem to run continuously 24/7 except for defrost cycles.
I'm coming to the conclusion that the refrigerant must have leaked out of the sealed system on this fridge, and I need to buy a new fridge.
Is there anything I might be missing? Should I get an appliance repair tech in to measure the pressure drop across the compressor to see if that really is the problem, or have I covered all the bases already and proving that it's a lack of refrigerant is just a waste of money?
--
nestork


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On 7/14/2014 3:25 PM, nestork wrote:

Is the condensor behind the fridge? Is there a bunch of horizontal back and forth tube, and wires that go up and down?
If this is the case, the top 1/3 or 1/2 of this assembly should be hot when the compressor is running.
If not, then very likely low freon. Please write back and ask questions if you wish.
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Christopher A. Young
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On Mon, 14 Jul 2014 21:25:09 +0200, nestork

wants to figure out the problem. If he's slowing down on the testing and hasn't done your pressure drop thing, ask him to do it, if you still want it done.
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Hi again.
This fridge is equipped with a test plug.
According to the fridge's wiring diagram, measuring the resistance between the orange wire of the test plug and the blue wire going to the defrost timer will measure the resistance across the defrost heater. I did that and measured 38.7 ohms. The factory spec is between 34.6 and 37.5, so it's a little out of range, but at least I know that the defrost heater is in one piece.
According to the fridge's wiring diagram, measuring for continuity between the orange wire of the test plug and the brown wire going to the defrost timer will determine whether the defrost thermostat is making the circuit to the defrost heater or breaking the circuit to the defrost heater. I did that and got no continuity through the defrost thermostat. So, the defrost thermostat is breaking the continuity to the defrost heater.
That means that the defrost heater is good, but the defrost thermostat isn't allowing any current through that heater, so I still could have a block of ice around the evaporator coil.
In this case, a good assessment would be to unplug the fridge for a few days to allow that ice to melt, and then fire up the fridge again. If it freezes water initially, but then the freezer compartment warms up, then I've got good evidence to believe the defrost thermostat is on the fritz and preventing the defrost heater from working.
Thanks for everyone's input.
--
nestork

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On 7/14/2014 7:16 PM, nestork wrote:

Termination thermostat closes about 25F (or colder) and opens about 45F or warmer. Was the freezer cold when you tested?
Do you see snow on the panel that covers the evaporator?
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On Monday, July 14, 2014 7:16:19 PM UTC-4, nestork wrote:

Based on what you describe, it sounds to me all you're seeing is that the defrost timer isn't at the point in time when it closes the switch to turn the heat on. Which is what you'd expect to see, because it only occurs a very small percentage of the time.
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'Stormin Mormon[_10_ Wrote: > ;3259684']

Well, it wasn't as cold as it should be, but manually defrosting the evaporator coils and putting the fridge back into operation with clean evaporator coils will at least tell me whether excessive ice accumulation on the evaporator coils was the problem before.

No, not at all. In this fridge, the evaporator coil is located UNDER the freezer floor. To remove that freezer floor, I have to remove both the freezer compartment door and the fridge fresh food compartment door.
I will do that with the fridge running so as to preserve the frost pattern on the evaporator coil.
I defrosted the fridge manually by unplugging it, propping the fridge and freezer doors open, directing the melt water tube into a large shallow pan on the floor behind the fridge and letting any frost on the evaporator melt.
I collected about a quart of water, which to me means that the evaporator was pretty iced up.
Once I was convinced that the evaporator coils were fully defrosted, I put a plastic cup of water (covered by a jar lid) in the freezer compartment and plugged the fridge back in. This test will determine whether the fridge works properly when the evaporator coils ARE NOT frosted up. If that water still doesn't freeze, then I'll look at the frost pattern on the evaporator to see if it indicates a low refrigerant charge. If the water does freeze, then I'm convinced the problem is excessive frost accumulation on the evaporator coils, and I'm gonna blame the DTS for that cuz the defrost heater shows continuity.
If replacing the defrost termination switch still doesn't solve the problem, and the evaporator is frosted up along it's full length so it's not a weak refrigerant charge, then I'm willing to call in an appliance service tech to figure out what's wrong. I figure that if I go this far and still can't solve the problem, then I'm prepared to pay for a service call. For 99% of appliance problems, going as far as I have will have determined the cause of the problem and the solution. I'm willing to pay for that remaining 1 percent that I can't solve myself.
On this fridge, I have to remove the fridge and freezer compartment doors to remove the freezer compartment floor. The evaporator is under the freezer compartment floor. I have to bend the hard plastic freezer floor to get it out of the freezer compartment. So, I'll let the fridge fully defrost a second time so that the plastic I'm bending won't break. Then I'll remove the freezer floor and plug the fridge back in to see how the frost forms on the evaporator.
--
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On 7/15/2014 7:16 PM, nestork wrote:

Sounds like you're closer to diagnosis.
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Well, after manually defrosting the fridge by unplugging it and leaving it to warm up for a few days, I plugged the fridge in and left a plastic cup of water in the freezer compartment overnight. Normally, that's long enough to freeze the water into a solid block of ice.
But, the water didn't freeze.
And, apart from defrosting itself once every 20 hours or so, the compressor and evaporator fan were running continuously overnight so far as I can tell.
My next step is to take the freezer floor out of the fridge so I can see the evaporator coils and how frost accumulates on them. At this point I'm expecting to see proof of a low freon charge, and am thinking I'm going to be buying a new fridge shortly.
I'll leave the fridge running with the water in a plastic glass in the freezer for another day or two just to be certain that it's not gonna freeze. Then I'll take the freezer floor out and see what's happening at the evaporator coil.
--
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On Wednesday, July 16, 2014 11:24:21 AM UTC-4, nestork wrote:

Why bother? If the compressor is running constantly, the fan in the freezer is working, and it's been defrosted so it's not blocked by ice, why do you need to see the coils? It's obviously a major failure and it's not cooling.

What good would it be if it finally froze after two days? If the freezer can't freeze over night, it's screwed.
Then I'll take the freezer floor out and see what's happening

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On 7/16/2014 11:24 AM, nestork wrote:

refrigerant charge "freon".
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On Wed, 16 Jul 2014 09:42:18 -0700 (PDT), trader_4

If the fan is blowing air, you can feel where it is coming out. If no air, check the coil. If air is passing, the coil is not frozen and the unit is probably trash, not worth fixing.

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On 7/16/2014 1:57 PM, Ed Pawlowski wrote:

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On Wednesday, July 16, 2014 2:48:58 PM UTC-4, Stormin Mormon wrote:

That would seem to depend on why the refrigerant is gone. Unless something has failed refrigerant doesn't just disappear.
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On 7/16/2014 4:54 PM, trader_4 wrote:

Add some, and see how long it lasts. If it's a slow leak, lasts year or more.
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On 7/16/2014 2:48 PM, Stormin Mormon wrote:

Easy for you. Call a pro and it will be $300.
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On 7/16/2014 9:09 PM, Ed Pawlowski wrote:

I'd be curious to hear from folks who had refrigerant "freon" added to refrigerator. what did it cost? I'm very possibly far too cheap.
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Ed Pawlowski wrote:

For 300.00, OP can buy new one same size, I am sure.
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'Stormin Mormon[_10_ Wrote: > ;3260495']

Stormin:
Here in Canada, refrigerants are treated like toxic waste. You have to have a license to work on AC and refrigeration systems in order to buy refrigerants, and even then you have to meticulously document what happened to the refrigerants you removed from equipment. You can't just buy a piercing valve and "fill er up" like you could in the 1980's. If I have a refrigerant leak, the service tech would have to evacuate the remaining refrigerant in the fridge, find the leak and fix it, re-evacuate the refrigeration lines in the fridge, and then add new refrigerant. The cost for labour is roughly $300 to $400, and any parts (like a new compressor) would be on top of that. It makes more economic sense to buy a new fridge.
Trader: You're wondering why I want to bother seeing how the frost builds up on the evaporator, and why I just don't chuck the fridge?
It's because I'm old enough to have been wrong in my assumptions more than once, and I don't want to be wrong on this fridge cuz a new fridge will cost me about $400. If I can see that the frost isn't forming uniformly over the whole evaporator coil, then I know it's a weak refrigerant charge, and I have no hesitation to salvage old parts from the fridge and phone a metal salvage company to pick up that fridge. However, I don't feel comfortable throwing the fridge away unless and until I see how the frost accumulates on the evaporator coil.
--
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On 7/16/2014 10:48 PM, nestork wrote:

CY: The US has the same regulations. Or some what similar. When I got my EPA card, we were told that if the system has less than 50 pounds of refrigerant, it's legal to keep topping it off. Might be expensive and impractical, but it's legal. For household refrig, I don't have any moral problem with adding a couple ounces. I can imagine that many techs would want to go the recovery and leak check route.

CY: You can also check for heat on the condenser coils, that's a good indication of charge.
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