1952 GM Frigidaire SR-60 Refrigerator Thermostat (Cold Control) Freezing

scott_h

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Jan 12, 2019
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Here's my story on my refrigerator. I think I have it fixed for now but please comment as the hive knowledge has been very helpful. I am an automotive guy with A/C knowledge in that world. Some of it crossed over and some does not.

I picked this refrigerator up 7 or 8 years ago from craigslist and it has been pretty good. The model number SR-60 and I believe it's from around 1952. When I got it the door seal was crumbling apart as was the wiring. But it still ran and everything seemed to work pretty well. I cleaned it up, gutted the insulation, rewired everything but the light (it was OK). I painted it red, replaced the door seal and it has been flawless as a beer fridge in my garage. Exactly as I hoped for. It needed to be defrosted every few months as this was in Atlanta.

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scott_h

Premium Member
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Jan 12, 2019
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Sometime last year I went to get a beer and it was frozen. It didn't take long to find that the contacts in what I call the thermostat (I hear it called the cold control often though). The easy part was diagnosing it. I tried to file the contacts but after 68 years of opening and closing the upper contact in the photo really had so little left of it. Between the thinness of the contact and me filing on it and maybe bending the spring it is on, it was not going to make it. That little contact is maybe 3/16" in diameter at best.
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I went to the local appliance parts place in Atlanta on the recommendation of a few friends and there was a lady there I was told to ask for. I showed her my thermostat and asked her how close could she come to it. She came back with a Ranco A30-2210. Now I am not in the appliance service business and don't claim to be so I can only take her advice and give it a try. She charged me close to $60 which I find later online for a quite bit less but she was willing to give me a hand and spend the time with me so I am OK with that.

I bend up the end that goes on the evaporator to try and match the same contact area as the original and get it pretty close. The original is on the bottom, new on on the top. This has a screw that attaches it to the side of the evaporator which is the freezer.
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scott_h

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I put the whole thing back together and the good news is it works. The bad news was the temp was way too warm, like 53F warm. Turning the temp knob on the thermostat moved it a little but we were a long way from beer temperature. So, my thinking is that the thermostat is getting cold enough too soon and is turning off too early. Since the end of the thermostat capillary tube is attached to the side of the evaporator, I need to find a way to make it "less cold". The zigzag capillary tube mounts up against the evaporator with a plastic mount to insulate it a little bit from direct contact. Well, I make up a bunch of different plastic pieces that are the same shape as the original but different thicknesses. I try all sorts of combinations from adding thickness to removing nearly all. Regardless of what I try I am having no luck, it is either too warm, the compressor stays running and it goes below freezing. Oh, I am measuring the air temp in the center of box with a thermal couple hanging from the center rack with a display on top.

The capillary tube attaches about half way back on the left side of the freezer (evaporator). The brown wire you can see hanging is the thermal couple wire that I used as a remote temp sensor so I could watch the air temp inside the center of the box without opening the door.
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scott_h

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In the middle of all of this I get a new job with the same company but have to move. With moving and getting a new house set up this all gets put on hold as there's just not enough Scott to go around.

Fast forward six or so months and I am now in Phoenix and ready to get back into this and make it work. I am pretty much out of patience and just want it working. I admit that I forgot all about this site and was just going to bull my way into getting it to work. Next I tried to adjust the calibration of the thermostat with the little sealed calibration screw on the side of it. They seal it with red paint and use a Tor-x screw to (try to) keep people like me from messing with it. So, now I am adjusting the screw and changing the shim/insulators on the capillary tube and although I can make some progress I still go from too warm for beer to freezing. I make a change and let it run for a few hours to stabilize and I am still missing the mark. Too warm or freezing.

My thinking about now is that the OE thermostat is calibrated for the specific evaporator temperature range which will then correlate into the correct box temperature range. Since the OE thermostat isn't available, how many different thermostats do I need to try before I can get the right one? It is now after the fact as you will see here in a little bit but I sincerely ask, what did I miss here??

Here's that little "never adjust me" screw.
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scott_h

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Off to Google I go. I search for something like "programable refrigerator thermostat". It doesn't take long before I come across the Inkbird ITC-1000. I then search "ITC-1000" and find that the home brew crowd loves this for maintaining the exact temperature for the super special IPAs that they make. Score!! Amazon carries this for $15.99, double-score.
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I read all of the specs on this thing but I already know that the home brew crowd is making this work so there has to be a way. The part that I am really liking is that this will operate the compressor by measuring the temp of the air (beer) not the evaporator. Need to remember to keep the door closed but not too worried about that. The specs say that it is strong enough to switch on and off 10 amps at 120VAC. Back to the Frigidaire with my ammeter to figure out how many amps this thing pulls. Under normal operation the compressor pulls about two amps. I then try to watch the start up amperage but my super fancy $400 Fluke meter can only capture up to about 7 or 8 amps because that higher load is so quick. . I switch the meter over to MIN/MAX and am able to capture 12.0 amps every once in a while and most often on a hot restart. I am manually starting the compressor with a jumper because there is no thermostat. A hot restart is when the compressor starts when the high side pressure is still high because it just turned off. Not something that should happen but, the good news is that the ITC-1000 has a setting for a minimum time the compressor must be off before it will allow it to restart. The default is 5 minutes so I think I'll be OK. Off to order it.
 

scott_h

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Alright, where to mount the thermostat and the fancy red LED display. There are two main driving factors for me in locating this. One, I am not going to hack up the vintage look with an LED panel. And Two, I don't think I can mount it inside of the refrigerator although that would be nice. The thermostat does not look to be waterproof and this old box will need to be defrosted, a lot less here in the desert, but will still need to and that puts water everywhere. I could use one of those plastic waterproof project boxes but this refrigerator is already pretty small and I want to keep as much space as I can.

To the back it will go.

I made a fancy sheet metal bracket and wired it up. The easy part was all of the wiring I needed access to was all right there. The temp sensor needed to be routed to inside of the box but 100% of the other wiring was all between the plug coming in and the relay.

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The little black wire is the temperate sensor and there is a slot in the grommet for the refrigerant line that the wires fits in perfectly. This takes the sensor inside.
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Yes, I tied up the wire so it wasn't laying across the top of the condenser.

I installed to original thermostat to fill up the hole in the side of the box and routed the sensor wire so it sticks out just enough to get away from the side.
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scott_h

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Jan 12, 2019
Messages
15
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GA
At the end of the day, it works. I left it running for a couple weeks and watched the display often as well as I still had the thermocouple installed. I moved the tip of the sensor to all three of the shelves and there was no change in the temp. The thermostat has the ability to program a set temperature that you want the circuit to open and the compressor to turn off. You then program in the temp range you want it to operate within. The default is 3 degrees IIRC. The temp will stay within that range incredibly well.

When making the decision on mounting the thermostat in the rear I was thinking about how I would not be seeing the display without sliding the fridge out. My thinking was how often did I check the actual temp before I had these problems? Well, with a thermometer, almost never. But I checked it every time I had a beer.

One last thing before I wrapped this up was the shelves. The spacing on the wire racks is about terrible for beer bottles. They are just far enough apart that the bottles will tilt with a little movement and then fall over. I wanted something different but wasn't going to remake the whole thing. I went to Metal Supermarket with the idea that I would get some expanded sheet metal in stainless. Well, $$$$ ended that thought. Over $120 for what I wanted. Off to the "drops" section out back. "Drops" for those who have never bought steel are the smaller pieces that "drop" off of the bandsaw or shear when cutting a larger piece. Not big enough for most customers but too big to throw away. I found a couple pieces of perforated (holes punched in) steel for $12. Another score. Etching primer and gloss white made them match. There used to be crisper drawers on the bottom of the fridge that I took out to make more room. That meant that the beer had to sit on the floor of the box. There were a few protrusions to keep the floor from being flat so I elevated this perforated steel on the bottom to make a nice flat shelf.

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Cleaned up the mercury thermometer mounted to the shelf.
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As I type this, there's a bottle next to me and it's perfect!!
This was nearly a year getting it all sorted and fixing the shelves to keep the bottles from tipping.

To the pros here, was there an easier way with a mechanical thermostat? I will say that even if there is a good replacement, the programable one is pretty easy to install and wire up and at less than $20 is really hard to beat
 

Dan O.

Appliance Tech
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The finished product looks very nice and I'm glad you were able to modify a control system for it. I just wanted you (and others) to know that there is still a brand new, original thermostat currently available for that unit. It might have saved a bit of effort.

LINK > Frigidaire SR-60 Thermostat

Sometimes old stock of functional parts can still be found. Techs getting out of the business often liquidate there truck stock that has been kicking around for ages.

Dan O.
 
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scott_h

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Jan 12, 2019
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Wow, thanks Dan! I went ahead and picked up the thermostat you linked. I really like having this fridge and am working hard to keep it going.
 

scott_h

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Jan 12, 2019
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There was another thread here where someone posted a complete image of the original wiring diagram. Thanks!!! Here is all I had to work with before I found that here.
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Here's the complete one just to save someone from having to find it.
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And here is how I wired the Inkbird ITC-1000
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scott_h

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Jan 12, 2019
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GA
While I am at it, does anybody have a need for the Hydrator drawer and an additional wire shelf for this SR-60 Frigidaire? Making this a beer fridge has left these two parts unused. I am going to post it over in the for sale as well. I know I usually only come to the vintage section.

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Dan O.

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scott_h said:
does anybody have a need for the Hydrator drawer and an additional wire shelf for this SR-60 Frigidaire?


Someone might be interested. Those are the types of parts rarely found later in an appliance's life. It might take a while to find a new owner though. If you're not in a rush, yes post them here so they can be found.


Dan O.
 

scott_h

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I have already put them in a box and put them away on the top of a shelf. It was either that or toss them. Just can't do that. Hopefully they can find a new home.
 

DaveRite

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Dec 15, 2020
Messages
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Location
Michigan
Scott, I may be interested in you extra hydrator, i have an AO60 that looks just like yours. Do you happen to have the part number for the cold control? I bypassed mine just to keep it going, but have to unplug regularly to prevent freezeup.
 

scott_h

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GA
DaveRite,

The NOS Frigidaire part number is 9948865. Dan O found that number and it is the correct one for this. The new LED one is Inkbird and that number is: ITC-1000. Someone contacted me a few weeks ago about the NOS part I had who needed it so I sold it to them. I figured (hoped) that my replacement will last a long time and if it doesn't it would take about 5-10 minutes to swap it out vs. undoing the new wiring and installing an OE one.

If you want the hydrator let me know. I would rather deal with shipping after holiday.

Good luck!
Scott
 

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