How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask John Your Own Question
John
John, restaurant equipment technician
Category: Appliance
Satisfied Customers: 2132
Experience:  25+ years experience. I'm now employed by a commercial cooking equipment service company
22250861
Type Your Appliance Question Here...
John is online now
A new question is answered every 9 seconds

I have a 427r. last week, the unit out if nowhere has the

Customer Question

I have a 427r. For the last week, the unit out if nowhere has the temperature in both the top and bottom start creeping up. Fan is blowing but not cold. I shut the unit off and then back on at the breaker and then it works fine again...a day or 2 later...same problem, same solution. Any ideas?
Submitted: 8 months ago.
Category: Appliance
Expert:  John replied 8 months ago.

The first thing to do is inspect the condenser coil to see if there is a layer of dust blocking the air flow through it. If there is, vacuum it with a ShopVac to remove it.

If this doesn't restore proper cooling, please get back to me. Thank you.

Customer: replied 8 months ago.
Thanks John. Already have done that.
Expert:  John replied 8 months ago.

OK. Thank you. I'll look further for parts information, and I'll get back to you.

Expert:  John replied 8 months ago.

Your cooling system control board uses a heat sensing thermistor to determine the cooling set point. Its part number is(###) ###-#### If you call guaranteed parts, inc. at 1-***-***-****, you can order the part. There is a thermistor for each section. If you need an owners manual, type the words "sub zero 427r manual" into your Google search box, and choose from the websites offered there. If you need more help, please get back to me. Thank you for choosing JustAnswer.

Customer: replied 8 months ago.
Thanks John. Why would switching the unit off and back on at the breaker fix the problem temporarily?
Expert:  John replied 8 months ago.

The control board tends to erase the voltage values in it, when the power is removed. Since thermistors are voltage producing devices, it takes a bit of time for the board to determine that there's a problem with the signal it's receiving.

Customer: replied 8 months ago.
Thanks again John. The same issue happens at the same time on both top top unit (wine fridge) and bottom fridge drawers. Is this one part you mention above (thermistor) that controls both?
Expert:  John replied 8 months ago.

There is one for each section.

Customer: replied 8 months ago.
Wouldn't it be unlikely they both went bad at same time? To help, the control board was replaced back in November. Issue above only started several weeks ago. Not sure if they could be related
Expert:  John replied 8 months ago.

Before we go any further on thermistors, I want you to use a piece of note paper, or a paper bill, and insert it in several places around the door seal gaskets. When the door is closed, check to see if there is resistance to pulling the paper out. If you find spots where there's little or no resistance, you'll need to replace the gaskets. Please let me know what you find with this seal test. Thank you.

Customer: replied 8 months ago.
Thanks John. Let me give that a shot tonight and get back to you.
Expert:  John replied 8 months ago.

OK.Thank you.

Customer: replied 8 months ago.
John. Thinking more thru this. Unit runs on two separate compressors right? If the gasket is bad, it would have to be bad on both top and bottom. Unlikely. The problem occurred several weeks ago for first time and is impacting both the top and bottom parts of the unit in the same way. Am thinking has to be related to the new control board installed end of last year?
Expert:  John replied 8 months ago.

Yes. I think you're correct. The control board package part number is(###) ###-#### ***** it's available at www.certifiedapplianceparts.com. Door gaskets tend to deteriorate at the same rate, and it's a good idea to replace both, if one is obviously leaking.

Customer: replied 8 months ago.
Another question John. Could it be the relay on the compressor? Do these units have 1 or 2 compressors and relays?:
Expert:  John replied 8 months ago.

I'm sorry I didn't answer your question in my last response. There is a separate sealed refrigeration system for each section. The compressor relays are electromechanical, and very reliable. They rarely fail, and when they do the compressor won't start.

Customer: replied 8 months ago.
Got it. Thanks John. And 1 control board for the entire unit? In which case, must be the control board.
Expert:  John replied 8 months ago.

That's correct.

Expert:  John replied 8 months ago.

Do you need any more help, before your request times out?

Related Appliance Questions