Subzero 532 won 't get down to temperature - temp fluctuates

SimonLes

Premium Member
Joined
May 13, 2019
Messages
5
Location
CA
Model Number
532
Brand
Sub Zero
Age
More than 10 years
Hi, my subzero was not cold enough so I had a repair guy come out. Refrigerant leak was diagnosed and he put a dye in, it worked fine for a while then got warm. We found dye inside.

The evaporator was replaced, at great expense. Still didn't get cold enough. The tech came out 3 times to "top it up", he said the Schraeder valve was also leaking. He put a new cap on it, and the last time he came here said it was no longer leaking from the valve and the system was still full. So that should be resolved

The reason he came the latest time was it is still not getting cold enough. He said the fan behind the evaporator was an after market item that was noisy, running too slow, vibrating and installed badly (spliced in with wire nuts). That seems fair enough because since he replaced it with a genuine subzero item it is way quieter. He also replaced the thermostat (the wheel that sets the temperature). His theory was that it was faulty and always sending an on signal. That led the compressor to overheat and shut off. By the time it had cooled down enough to start up it had to work so hard to get the freezer to temp, the cycle repeated.

Anyhow that theory seems wrong because nothing has changed. It fluctuates between about 8f and 28f. Quite quickly too, within a few hours. The case between the fridge and freezer doors is very hot, almost too hot to touch at times.

Given that it can warm up so fast, could this be something to do with the defrost timer getting stuck (i checked, the wheel is spinning) or the terminator switch being faulty? I've read some threads which suggest symptoms of those are it freezing up, not being too hot.
Any other suggestions? The fridge next to it works absolutely fine and the condenser was blasted with compressed air and vac'ed out twice during the time this has been going on.

TIA
Simon
 

Dan O.

Appliance Tech
Staff member
Joined
Oct 9, 2004
Messages
1,677
Location
Canada
The case between the fridge and freezer doors is very hot, almost too hot to touch at times.
The heater there is usually part of the condenser. What you described will occur if there's a problem with the main condenser, either plugged with dust, dirt and pet hairs, etc. or, the condenser fan not working. Both those things will also hamper its cooling ability.

The fridge next to it works absolutely fine and the condenser was blasted with compressed air and vac'ed out twice during the time this has been going on.
Maybe whatever he did affected the motor's operation now?

could this be something to do with the defrost timer
I doubt it but there might be a slim chance if the condenser isn't responsible. I however can't see the condenser not playing a big part. I'd suggest someone look into it.

Dan O.
 

SimonLes

Premium Member
Joined
May 13, 2019
Messages
5
Location
CA
Thank you Dan, your time to reply is very much appreciated. To conclude the thread I have an update.

I tried running a 12v RV fan on the condenser and bypassing the defrost cycle. That made no difference, apart from it didn't fluctuate in temperature, it just sat at an unhappy 8f all the time.

The repair guy came back, he said he checked the condenser out when he replaced the evaporator and thought it was OK. He said he put 5lbs of pressure in and mumbled something about stickers that should have come with the new part. He added another 5lb of pressure to take it up to 10lbs and now it is working fine. It sits at 0F consistently and although it goes up on the defrost cycle, which is understandable, it goes down again quickly. I am going to fill it with food (finally , it has been broken for about a year!) which should support that too.

Thanks once again, your advice really helped.

Simon
 

rickgburton

Appliance Tech - Moderator
Staff member
Joined
Jul 11, 2006
Messages
33,441
Location
Murray, Utah 84107, United States
He said he put 5lbs of pressure in.......He added another 5lb of pressure to take it up to 10lbs and now it is working fine.
R12 charge prior to serial number M681568 is 11.0 oz. R12 charge after M681568 is 7.0 oz. Suction pressure =16 PSIG

R134a charge = 10.0 oz. Suction pressure = 11 PSIG
 
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