Late 1940's GM Frigidaire Refrigerator ML-77 Starting Compressor Relay Question

FishMax05

Premium Member
Joined
May 17, 2021
Messages
22
Location
Holt, Missouri
Current draw was 1.8A - 2.0A. I didn't have a chance to record the starting draw.
I had a feeling you were going to say that about the trim pieces.. I was going to try to make them out of metal.
 

Tundrawalker

Premium Member
Joined
Nov 7, 2021
Messages
9
Location
Kitchener, Ontario
Glad to see all the recent activity on this thread for my very similar model GM Frigidaire. Gives me hope that I will be out of the woods soon. I have looked over most of the information and compared my hand drawn diagram to the more official ones here. As is common I had to replace the brittle wire insulation on my working fridge and now I am in a wiring harness quandry. When I plugged the firdge in after carefully trying to replace the wires under the cold box to the relay and compressor, I shorted out. My wiring up to the switch, light and thermostat seem intact and i haven't replaced it....yet. Here's the problem. The diagram shows 3 wires coming from the switch, light and thermostat in the cold box area. I have 4. In the diagram 1 wire doubles up on a terminal at the thermostat. In my situation I would guess that it is not doubling up on that thermostat terminal as I have 2 wires returning from the thermostat area of the fridge and 2 wires returing from the switch area. My guess is that the extra wire returing from the switch area which in the diagram doubled up on the thermostat after routing past the light would go to the Number 1 screw on the YT Relay (the bottom left). Now here's the kicker, I have continuity across all terminals, hence why my circuit blew when connecting to AC. Ugh. Thoughts on what to do to get this fridge cold again? First image is my new wiring, secong image was my wiring schematic before taking apart, third image was the original wiring before my new replacement.
 

Attachments

  • 11-07-21.jpg
    11-07-21.jpg
    82.6 KB · Views: 110
  • IMG_8002.jpg
    IMG_8002.jpg
    168 KB · Views: 104
  • IMG_7999.jpg
    IMG_7999.jpg
    381.1 KB · Views: 113

rickgburton

Appliance Tech - Moderator
Staff member
Joined
Jul 11, 2006
Messages
44,783
Location
Murray, Utah 84107, United States
When you replaced the brittle wires, did you connect the wires in the right spot on the relay? Your pictures only show me a relay with wires connected to it. If you're asking if the wires are connected correctly, I couldn't tell you without knowing what the other end is connected to. Is there a wiring diagram attached to your machine?
 

Tundrawalker

Premium Member
Joined
Nov 7, 2021
Messages
9
Location
Kitchener, Ontario
Thank you Rick for your reply, yes to the best of my knowledge I replaced exactly as it was. I know that my wires going to the compressor are correct, Which is also verified by the multiple schematics as posted here on this site. I had 2 double lead wires coming down from the cold box to the relay. One set had thicker insulation wiring and the other was thinner. At the time i had no idea where they were going as I hadnt opened up the finish trim around the cold box yet. I think what i will do next is disconnect everything to the relay and then reattach 1 at a time and check my continuity with each wire. Does that make sense?
 
Last edited:

rickgburton

Appliance Tech - Moderator
Staff member
Joined
Jul 11, 2006
Messages
44,783
Location
Murray, Utah 84107, United States
Take a few pictures of the machine and post them here. Take a pic of the back of the machine, compressor compartment and wiring, front of the machine with the door open and the cold-control.
 

FishMax05

Premium Member
Joined
May 17, 2021
Messages
22
Location
Holt, Missouri
Hi All, I am still working on my fridge(s). Once I have them completed I will update all with my schematic and dims of "breakers".

Rick, to answer your question, I have a buddy that is a sheet metal worked. Our plan is to make the breakers out of stainless steel. I will keep ya posted on this as it is one of my winter projects.

In other threads, I have seen folks are using Rockwool for their insulation. I was considering using R15 for mine. Thoughts?

-Fish
 

Tundrawalker

Premium Member
Joined
Nov 7, 2021
Messages
9
Location
Kitchener, Ontario
here you go. There is no visible schematic on the back. There is a glued piece of paper but it's contents are faded.
 

Attachments

  • GM Frigidaire-11.jpg
    GM Frigidaire-11.jpg
    214.9 KB · Views: 98
  • GM Frigidaire-10.jpg
    GM Frigidaire-10.jpg
    201.5 KB · Views: 96
  • GM Frigidaire-8.jpg
    GM Frigidaire-8.jpg
    204.9 KB · Views: 101
  • GM Frigidaire-7.jpg
    GM Frigidaire-7.jpg
    178.2 KB · Views: 98
  • GM Frigidaire-6.jpg
    GM Frigidaire-6.jpg
    238.7 KB · Views: 102
  • GM Frigidaire-4.jpg
    GM Frigidaire-4.jpg
    239.9 KB · Views: 98
  • GM Frigidaire-3.jpg
    GM Frigidaire-3.jpg
    195.3 KB · Views: 93
  • GM Frigidaire-2.jpg
    GM Frigidaire-2.jpg
    184 KB · Views: 95
  • GM Frigidaire-1.jpg
    GM Frigidaire-1.jpg
    209.5 KB · Views: 124

rickgburton

Appliance Tech - Moderator
Staff member
Joined
Jul 11, 2006
Messages
44,783
Location
Murray, Utah 84107, United States
There is a glued piece of paper but it's contents are faded.
LOL that's the thing I was most interested in.That looks like a YT relay. It's wired like this:
R-Early relay (2).jpg

Check your relay and see if the numbers and letters match up. This shows three wires and you said you have four wires. In this diagram the thermostat has two wires on one terminal. If you were to take the wire that goes to the light bulb, off the thermostat and connect it to 1 on the relay, nothing would change. It's still connected to the same wire only in a different spot. Except, now you have four wires instead of three.
 

Tundrawalker

Premium Member
Joined
Nov 7, 2021
Messages
9
Location
Kitchener, Ontario
Thanks, I alluded to this previously. I am going to disconnect and reconnect one at a time and see if i can track down my issue. plus I will crimp eyelets on all the wire ends to make the screw connections easier.
 

Tundrawalker

Premium Member
Joined
Nov 7, 2021
Messages
9
Location
Kitchener, Ontario
Okay, after 10 months I am back on this to hopefully solve this challenge. Let's review before moving forward. I had a working fridge with a YT switch which needed it's wiring replaced due to brittle insulation. I replaced the wires at the point that they dropped below the box into the compressor area. I rewired the switch properly (blew a fuse) the last thing i was going to due was check the continuity of the wires. here are my findings. The wires coming down from the thermostat which connect to screw "L" and "1" have continuity (!?!) The wires coming from the door switch/Light (I have 2 not 1) do not. The wires going to the compressor attached to terminals "S/M/2" and "W/R/B" all have continuity between them !?! If I hook all the wires up every terminal has continuity between all of terminals no matter which order tested. None of which makes sense to me. I am ready to upgrade to a modern relay if it gets the fridge working again but I don't know if that would solve anything in it's current state.
 

Old Fridge Guy

Appliance Tech
Joined
May 5, 2021
Messages
115
Location
67748
From the compressor to the relay, W goes to 2, then R goes to S, then B goes to M. Facing the compressor, from left to right the terminals are W, R, B. The number 1 and 2 terminals on the relay are "dummy" terminals. They don't connect to anything inside of the relay. The other terminals will all have continuity between them when the compressor is not running. That's normal. When the compressor is running you will not have continuity between S and M on the relay. This is because the start winding is pulled out of the circuit by the relay when the compressor motor has started and is at running speed.
 

Tundrawalker

Premium Member
Joined
Nov 7, 2021
Messages
9
Location
Kitchener, Ontario
Okay, I held my breath and plugged it in. It works. Kinda. Compressor is warming up I guess. At least I didn't blow a fuse but I did get a bit of a zap touching the frame which is what started this whold journey in the first place with the rotting insulation. The new plug I added has a third prong so I am gonna ground the frame. Hopefully that should work?
 

Old Fridge Guy

Appliance Tech
Joined
May 5, 2021
Messages
115
Location
67748
Sounds like you're heading in the right direction. Double check the terminals at the compressor. Make sure you don't have any bare wire or a connector touching the compressor shell. I gather you didn't replace the wiring from the relay to the thermostat, correct? Did you completely replace the wires from the relay to the compressor? Or are we dealing with splices? Splicing should be avoided. Since you're still getting a shock, further investigation is needed. Do you need guidance for replacing the wiring from the relay to the thermostat?
 

Tundrawalker

Premium Member
Joined
Nov 7, 2021
Messages
9
Location
Kitchener, Ontario
All new wiring below the box. I didnt replace inside the box area as it seemed relatively intact. I did pull the side covers off and traced the wire as far as i could, up to the switch and along the bottom cover before it hides inside the walls towards the thermostat. I didnt really want to investigate further as I didnt feel it was warranted. I’ll add the ground and see where Im at after that.
 

Old Fridge Guy

Appliance Tech
Joined
May 5, 2021
Messages
115
Location
67748
Ok, did you notice any dampness in the insulation between the liner and the cabinet? If so that could be the problem. Also, the thermostat was originally wrapped with a moisture barrier tape. If it was in poor condition you should wrap the thermostat with electrical tape to be sure the terminals are not touching the metal liner or the cabinet. It will also help keep moisture out of the thermostat area.
 
If you feel that you have benefited from this site, and would like to show your appreciation.
Top