Thread Number: 81688  /  Tag: Refrigerators
Troubleshooting Antique Refrigerator - Monitor Top DR D2...
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Post# 1056991   1/9/2020 at 08:42 by turbokinetic (Northport, Alabama USA)        

This will be a (mainly) video documented repair attempt on a very nice condition DR Monitor Top. The information I received is that it was restored years ago and used as a backup fridge until recently. One day, it was found to be running but rattling, and not cooling. It was taken out of service at that point. Otherwise, I have no history on it. It looks great, though. 

This is a spare-time project, so there may be delays between video postings; but rest assured I will share the job to the end, regardless of the outcome. 





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Post# 1057000 , Reply# 1   1/9/2020 at 10:50 by jeff_adelphi (Adelphi, Maryland, USA)        

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I'm happy the GE made a safe trip to your place. I know it's in good hands now, and I look forward to seeing what it's problems are. It was restored about 20 years ago, maybe just a repaint, and worked well until last year. It always ran fine, but stopped cooling one day. I watched the video you posted, and the chattering relay is a new problem, the move probably caused the already bad connection to fail.


Hope you can find a use for the Frigidaire motors and evaporator coil I sent along. They were saved from a junked ref. years ago, and just could not throw them out.   Jeff

Post# 1057001 , Reply# 2   1/9/2020 at 11:02 by turbokinetic (Northport, Alabama USA)        
Good info!

Hi Jeff. Thanks for the additional info!  


I do appreciate the motor and evaporator. The motor looks pretty much in like-new condition. That must have been a large model, such as a W-10 or something along those lines. I have an grey and white porcelain two-door AP-9 which I plan to restore some day, which needs a motor - so that will go to good use!



Post# 1057201 , Reply# 3   1/11/2020 at 00:03 by turbokinetic (Northport, Alabama USA)        
Some more troubleshooting work....

Video is long but contains a lot of info...



Post# 1057232 , Reply# 4   1/11/2020 at 08:13 by toploader55 (Massachusetts Sand Bar, Cape Cod)        

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Your videos David are better than anything on TV or Streaming Access.

And the back ground noise of the Vintage Piston compressors while you talk just enhance the whole experience.

Thank You again for a very detailed Educational Tutorial and efforts for Keeping great history alive.

Post# 1057245 , Reply# 5   1/11/2020 at 09:48 by turbokinetic (Northport, Alabama USA)        

Thanks Eddie.  The one with the loud repulsion-induction startup is my 1926 Frigidaire M5-2. It has the first design air-cooled condenser used by Frigidaire.  It has a 1-cylinder belt-drive compressor, which makes the tocking sound you hear. I wish it weren't so loud but not gonna mess with it as long as it's working.  

Post# 1057291 , Reply# 6   1/11/2020 at 20:59 by combo52 (Beltsville,Md)        
DR-2D Diagnosis

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Wow, David that was interesting, it was fascinating to see you check out this inoperative GE MT.


It often seemed that some of these refs would run forever, but at least my brother Jeff won't feel like he gave up too easily.


It will be interesting to see how you fair with the Gas Servel when you get a chance to work on it sometime.


I may have to get your help with engineering a fix for our Whirlpool 29" combination transmissions, I will text you some pictures some time.


John L.

Post# 1057359 , Reply# 7   1/12/2020 at 10:26 by turbokinetic (Northport, Alabama USA)        

John; I do find it interesting to check out the old Monitor Top fridges.  This ended up a very long message, and for that I apologize.

The DR models (those with the open coil condenser) were the first and were a bit of a learning curve for GE it seems. I've done a lot of reading on them and talking with other collectors and enthusiasts. It seems that GE learned about the shortcomings early-on and made a lot of improvements during production.  A combination of two design elements together in the system makes the DR machines very finicky. They have a metering device which is normally closed, until refrigerant liquid is present; combined with the large volume of the compressor housing being on the high side of the system. This makes the system incredibly sensitive to any sort of noncondensible gases or air in the system. There is a trap in the line between the condenser and float, so unless the system is completely free of noncondensibles, they will collect in the float chamber, and with the uphill trap in the lines, this will prevent liquid from filling the float chamber. Since the float is normally closed in the absence of liquid, this results in a no-circulation (blockage) situation. The large volume of the high-side compressor housing will accommodate the entire refrigerant charge when this happens, leading to the rattling noise when the refrigerant is at a high level in the sump.


The manuals explain that SO2 systems normally never develop noncondensible gases except if the low side has a leak (it operates in a slight vacuum) or if the motor has been severely overheated. 


This one seemed to sound OK initially, but I noticed some ominous signs. First, the bad contact between the control and the baseplate was the main winding circuit. If this circuit were intermittent or had a high resistance, it would provide low voltage to the motor all the time it was running. Another ominous sign was the amount of time it took for the compressor to build up to speed during a start. I have another working D2, and the startup takes a lot less time. It seems that with the DR Monitor Tops, this slow spin-up has preceeded winding failures in more than one case with other enthusiasts on the forum. There was a Kill-A-Watt meter in the circuit during startup, which was beeping indicating 15 amps or more current draw during the startup. That's also not expected. And finally, the ground resistance. I saw about 200KΩ if I remember, when making the first video.  On the day of the second video before startup, this resistance was much less. So as much as I hate to say it, I wasn't really expecting it to live but wanted to remain hopeful.

Cotton wrapped windings fail in an entirely different manner than modern enamel magnet wire windings. Whereas enamel magnet wire windings fail suddenly as soon as the coating melts and the winding turns short - cotton never melts. The cotton will char and become hard and brittle, with carbonized oil and charred cotton remaining in position. The damaged insulation will still remain in place, keeping the winding from making a dead-short, but it has become partially conductive and leads to resistive shorts which cause ground leakage high current draw. 


The SO2 interacts with the "vapors" from the chemical breakdown of the cotton, resulting in formation of noncondensible gases. This is by way of the cotton cellulose releasing water vapor as it degrades. The SO2 mixes with the water vapor and forms an acid solution. This immediately breaks down into hydrogen gas and some solid residues; in contact with metals. 


From what I have found, cotton is considered a "Class "0" insulation system. It begins slowly deteriorating above 90°C (194°F). This would be the maximum hotspot temperature of the winding, inside the coils. So the overall temperature of the motor would not have to be 90°C to have hotspots above the winding insulation limit.


So, one theoretical sequence of events leading to the failure would be:

1 - Poor contact developed between base and control, causing motor to have intermittent voltage and reduced voltage.

2A - Over time, the motor winding operated consistently at or above its temperature limit, leading to slow deterioration and release of NCG.

2B - Or, alternatively, the motor was overheated severely, once; by a control malfunction or improper repair / testing methods. This could have been decades ago.

3 - The NCG built up to a level requiring excess pressure to obtain flow through the high-side float metering valve.

4 - The compressor pulled into a vacuum or near vacuum, resulting in excessive hot-gas discharge temperature on the high side.

5 - The motor is cooled by high-side hot gas, which was entering the housing at an abnormally high temperature and low flow volume.

6 - The overheating continued for a period of time (years?), exacerbating the deterioration of the motor winding and creating enough NCG to stop the refrigeration cycle. At this point, the unit was taken out of service.

7 - The refrigerator was transported across country, with vibration and position changes causing the charred winding insulation to mechanically break apart.

8 - The lost insulation allowed the motor to developed multiple turn-to-turn, and winding-to-ground shorts.

9 - Attempting to run the motor in such damaged condition led to a complete failure of the winding.


I think that the reason the DR machines are so hit-or-miss is because you never know how far along the path to failure they really are when you acquire them.


The CK models were the final revision of the Monitor Top. They did away with the high-side compressor housing and went with a forced-oil cooled winding. There is an oil pump which forces oil through the winding and then sprays it against the inside of the compressor housing as a heat exchanger. These are the most reliable, with winding failures being nearly unheard of. They also have a better control and protection system, with many having dual overload breakers. 


The CK also has a direct connection from the compressor discharge, through the condenser, to the high-side float chamber. This ensures that a modest amount of NCG can be in the system and still allow the unit to function.


The Servel looks like it is in good shape, aside from the faded paint. The interior is immaculate due to the new door gasket. I did a little preliminary research and it seems that it has a natural gas burner orifice. I will have to locate an LP gas orifice in order to test it out. I've got too many things ongoing now to tear into it, so that will be a future project. smile


Feel free to text me the transmission pictures as well.




Post# 1057407 , Reply# 8   1/12/2020 at 21:46 by combo52 (Beltsville,Md)        

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Hi David, Thanks for all the detailed analysis of how this refrigerator likely failed, I have paid very little attention to these GE Mts over my career.


I knew they went through a lot of design changes over the years they were produced, I guess it is pretty impressive that an early design like this lasted as long as it did.


This GE MT DR ref belonged to a Whirlpool trainer who was in the Baltimore  region, he sold it to us when he was transferred back to Michigan 25 years ago because he knew my Brother and I liked old appliances and he did not want to move it again.


The Gas Servel was operated on natural gas, hopefully it can be converted to propane with just a different office, however some had a different burner as well for LP, I have service Manuels for the little later WP branded Servel refs, I may even have some Servel Manuels, I will do some digging.


John L.

Post# 1057412 , Reply# 9   1/12/2020 at 22:34 by Repairguy (Danbury, Texas)        

Incredible information! These old fridges donít have failure as an option when you are on the case.

Post# 1057435 , Reply# 10   1/13/2020 at 06:28 by toploader55 (Massachusetts Sand Bar, Cape Cod)        

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Could you please be a bit more detailed about the failures of Monitor Tops ?

LOL... Just Kidding.

Absolutely Brilliant dissertation. If General Electric were still a tried and true American Company, they would be fools not to hire you for design and engineering.

I just love your information. Thank You for sharing.

Post# 1057444 , Reply# 11   1/13/2020 at 08:10 by swestoyz (Cedar Falls, IA)        

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David - great video series on the DR! Thank you for taking the time to film, edit, and upload to YouTube. However, please don't apologize for any length of video you may publish. Your detailed analysis should take sometime and I for one appreciate you not rushing through anything.

Last week I found myself, hours later, watching the compressor rebuild of the Frigidaire M52 before I realized I needed to come back to it at a later time. Thank you for sharing, both out on YouTube but here as well!


Post# 1057546 , Reply# 12   1/14/2020 at 08:53 by turbokinetic (Northport, Alabama USA)        

Thanks for the comments on the videos!  


I don't mind making videos when time permits. After searching for and not finding info when I was needing it; I realize how frustrating it can be. I want to encourage others to appreciate the interesting history behind the everyday appliances we take for granted now. That makes it worth  it to me, to share some of what I do for my hobbies.



Post# 1057569 , Reply# 13   1/14/2020 at 14:45 by sfh074 ( )        
David .....

I subscribe to your channel but for some reason this video doesn't show up in your line up. I also searched on the keywords "general electric dr-d2" and still didn't show up either. Not sure why but thought I would mention it.

Bud - Atlanta

Post# 1057607 , Reply# 14   1/14/2020 at 19:42 by turbokinetic (Northport, Alabama USA)        

Bud, I appreciate  your subscribing to my channel. I sent a PM as to why the recent videos are unlisted. 

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