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MCBM920S1 Magic Chef Refrigerator stopped

rtfc

Premium Member
Joined
Jan 24, 2021
Messages
3
Location
Virginia
Model Number
MCBM920S1
Brand
Magic Chef
Age
6-10 years
I have a Magic Chef MCBM920S1 with a bottom freezer compartment, bought used, not sure about age - but looks 6-10 years old.

Noticed it had stopped running overnight with some water on floor - not sure if it was from icing up melting (never had seen any icing) or from food thawing.

Symptoms:
The light still works.
Compressor does not appear to try and start.
I hear a slight momentary hum when plugged in - removed interior panel - each time it is plugged in the evaporator fan runs for about two seconds then stops - light remains on.

Already tried:
New relay and overload
New capacitor
There is continuity across all compressor pins - none shorted to ground.

Use fridge as kegerator - no holes drilled - open door for picnic style taps - and it fits perfectly in bar area - bottom freezer puts kegs high, making hooking taps up easy. Really want to keep this for those specifics and it is hard to find replacement (< $1000) for this size and this configuration.

Any suggestions?

Corrected model number
 
Last edited by a moderator:

Dan O.

Appliance Tech
Staff member
Joined
Oct 9, 2004
Messages
4,245
Location
Ontario, Canada
The fans(s) and compressor are designed to run together. If they both fail to operate at the same time it is some part of the control system stopping them.

I have no personal experience with that product nor can I find any parts list, exploded views or wiring diagrams to see what possibilities there might be for that. If you can at least post a copy of its wiring diagram I might be able to suggest the components likely needing further scrutiny.


BTW The model number is MCBM920S1 (nine two zero) not MCBM92OS1

Dan O.
 

rtfc

Premium Member
Joined
Jan 24, 2021
Messages
3
Location
Virginia
Thanks Dan, I hate when manufacturer's use O's and 0's never can tell them apart unless side by side.

I can't hear the compressor trying to start, but it might be. Again the fan starts when I plug it in and runs about two seconds and stops.

I've attached wiring diagram that is on label and a pic of the control board.

Also has a Manufactured code on label, but I can't figure out code - could be made as early as 1989, 2000 or 2016. I'm guessing its older than I thought and made July 16, 2000, just a guess.

I said relay, meant I replaced the PTC, overload and capacitor. Found a replacement control board online, not terribly expensive, but sure would like to make sure that's the problem before I go sinking more parts into it.

Really appreciate your help.
 

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  • MCBM92S01 Control board pic.jpg
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Dan O.

Appliance Tech
Staff member
Joined
Oct 9, 2004
Messages
4,245
Location
Ontario, Canada
The picture is not very clear. As nears as I can see everything is connected separately to the control board.

rtfc said:
I can't hear the compressor trying to start, but it might be.

That would be necessary to know to make a diagnosis. If the compressor is but the fan isn't, that would leave a problem with just the fan. If both aren't, that would point to something in common with both, like the control system.

If you figure that out, it should point to the problem area. If both are acting the same, that either leaves the control or maybe the temperature thermister causing the board to do those things.

JMO

Dan O.
 

rtfc

Premium Member
Joined
Jan 24, 2021
Messages
3
Location
Virginia
Dan been a few weeks, just got back to working on this.

Some more information.

The evaporator fan was only trying to start then stopping because I had door open - duh.

Fan now runs all the time when unit is powered - and door is shut.

Bought a 3N1 hard start. No luck connecting it thru the control board - fan and light still work, but no compressor start - doesn't appear to even try to start.

Wired 3N1 directly to compressor and it runs and cools.

So problem appears to be control board itself or a temperature sensor.

What's easiest way to test which one of these it is? The control knob in the frig only has a very small board with wires behind it - no capillary line.

Thanks in advance.
 

Dan O.

Appliance Tech
Staff member
Joined
Oct 9, 2004
Messages
4,245
Location
Ontario, Canada
What's easiest way to test which one of these it is?

If you knew the resistance of the thermistors you could check their resistance. I do not know what that should be at any temperatures. You might be able to compare the reststance reading of the defrost thermistor to the fridge compartment thermistor to see how they compare although I do not know if they are suppose to be the same or different.

If the sensors were within specs, the control would often just be assumed to be the cause if it was not sending power to the compressor at all. I do not know if there is any way to directly test the electronic control. Often on cheapo appliance models there isn't. You could try asking Danby, just don't ho,d your breath.

JMO

Dan O.
 
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