Refrigeration advice

I ran across a used, Haier HEC SWX30N wine cellar on Craigslist. SWMBO's birthday is coming up, and I know she's been wanting one. The price was pretty good and the description stated it worked perfectly, in excellent condition. I met the seller, looked over the fridge, and cosmetically everything looked as described. Since we met at a central place, power wasn't available to see if it worked so I assumed everything was fine (I had no reason to doubt them, and the cellar had signs of use). Bought it, brought it home and let it sit upright for 24 hours just in case.

So I plug it in today, it jumps to life and I figure life is great, SWMBO is gonna be happy! I check on it 45 minutes later, and the temperature display reads "HH", the inside is near freezing (based on a thermometer I stuck in there). I can change the setpoint, but it doesn't do any good, it just keeps dropping to near-freezing.

Of course, the seller won't return calls or emails. Didn't really surprise me, but at least it's not dead. Worst case, I have a new fermentation chiller that I can hook up to a RANCO to use in the brewery, but I really would like it for its intended use.

It has electronic controls, mot manual. The display reads "HH", which means the cellar temperature is too high. The compressor is obviously fine since it is cooling like a champ. I don't have refrigeration experience, but I do have controls experience. Usually you run into "HH" and no cooling, but since I have the "HH" and it is trying to cool things down, it leads me to believe it's just a bad sensor (thermocouple or something like that).

Before I order a new sensor for this (which is only a few bucks) is there something else that could be causing this?

well, due to the overwhelming amount of advice I received (HA HA) I went ahead and bought a new sensor anyway, just to see if it works. There aren't really that many parts to this thing when you look a the exploded view online, so I'm fairly confident I am getting the right part to fix it.

Cost for the sensor: $3.99
(Although after paying tax and shipping I'm feeling like a prison b!tch)

Hopefully this takes care of it and gets it back to working condition.

jtucker101 said:

well, due to the overwhelming amount of advice I received (HA HA) I went ahead and bought a new sensor anyway, just to see if it works.

Click to expand...

Does it have a digital temperature display? The control board may be malfunctioning. Temperature sensors are very simple devices and rarely fail.

Good luck!

Yes, it has a digital temperature display. The temperature display works when I set the temperature to a specific setpoint, but when I lock in a setpoint, it returns to "HH". The display is designed to show "HH" or "LL" to indicate when the internal temperature is "out of range" (too low or too high). Since at freezing it's still showing "HH" I'm assuming the logic programming is set to fail high form a sensor failure(like programming a thermocouple to do so from a PID controller or PLC).

We'll see, hopefully this takes care of it.

Im not positive on refrigeration controls, but most sensors will read maxed range one way or the other when the wires are shorted or open. so your senor wire might have been cut/unplugged and is now reading HH all the time. If you can get to it, remove the sensor, check the wires and connections and re-connect it to see if you get a reading.

jtucker101 said:

The display is designed to show "HH" or "LL" to indicate when the internal temperature is "out of range" (too low or too high). Since at freezing it's still showing "HH" I'm assuming the logic programming is set to fail high form a sensor failure(like programming a thermocouple to do so from a PID controller or PLC).

Click to expand...

Assuming the temperature sensor is resistive, you could remove it and measure the resistance at room temperature. Common refrigeration thermisters read 10K ohms at 78F.

I was thinking along the same lines, so I removed the sensor and measured. Room temperature (approximately 75 degrees F) I get about .770K ohms.

I stuck it in the freezer, and it rises to about .991K ohms.

Something I noticed while taking the unit apart to remove the sensor...it's been removed before. Is it possible that there are different resistive ranges on the sensors and the previous owner installed the wrong one? It looks similar to the one I just ordered, minus the heat shrink around the sensor wires.

jtucker101 said:

I was thinking along the same lines, so I removed the sensor and measured. Room temperature (approximately 75 degrees F) I get about .770K ohms.

Click to expand...

Have you tried locating a manual (or calling the manufacturer) to see what the correct resistance range should be? It is suspicious that the sensor has been removed before, like someone attempted to fix it and failed.

I mean, it can only be one of three things: (1) faulty sensor, (2) open sensor circuit, or (3) faulty control panel.

closed for Columbus day...just my luck.

Haven't been able to locate a service manual, just a basic owner's manual. Even the Haier website doesn't show the model number I have.

Here's the extent of what I could come up with:

link

incidentally, I tried running the fridge without the sensor. When disconnected, the temperature display reads "EE" and an audible alarm sounds.
The control board knows when a sensor is NOT present.

jtucker101 said:

incidentally, I tried running the fridge without the sensor. When disconnected, the temperature display reads "EE" and an audible alarm sounds.
The control board knows when a sensor is NOT present.

Click to expand...

Yup, that rules out open sensor circuit. Sounds more and more like a faulty sensor.

great news...I received the sensor today from AP Wagner and connected it to the digital control board. Plugging in the unit and the display shows the proper temperature! I need to install the sensor in its proper location (have to wait for SWMBO to leave for an hour or so) to test an make sure it hold a programmed setpoint, but otherwise it looks like the new sensor fixed things.

granted I should have been much more discriminating and insisted on seeing the unit plugged in and running, but is there anything I can do/should do regarding the transaction? I still have 2 contact numbers and an email address to the seller. Should I post on warning on craigslist for others, or should I just let things go and consider myself lucky?

Cool!

Count yourself lucky and move on.

Ya, you got a good deal. Move on.

I mean, the seller didn't lie - it did cool. Just a little too well.

the seller FINALLY contacted me (once I threatened legal action) and told me it was in excellent condition prior to the sale, and that I must have broken the compressor when I transported it inside my house and plugged the unit in. I tried to explain to her that the compressor works great, it's the sensor that's bad...and a sensor doesn't magically morph into the wrong part. I told her there was no way the wine cooler could have EVER worked properly with that sensor, especially since it doesn't match the OEM sensor I ordered. she claims that it must have happened when I transported the wine cooler on it's side to my house.

if anyone wants an incredibly magic wine cooler sensor (that turned itself into a refrigerator sensor) please let me know. I have one for sale.

Hi jtucker101
My SWX30N has the same problem that yours did. Great job of troubleshooting and fixing. Can you provide more detail on the final steps of the repair? I got access to the back of the control panel. Are the sensor wires the ones that goes down the back of the unit under the plastic cover?

Yes, those are the ones. You should see those wires disappear into a hole with some foam insulation. In order to change out the sensor, you'll need to open the door of the unit and remove the 4 screws from the chill plate on the inside-rear wall of the chiller. I made sure the unit was room temperature, because once the screws are removed you'll have to carefully bend the chill plate down far enough to expose the sensor. It's mounted by a screw-clip...just loosen the clip and you should free up the sensor. It's a pain in the butt to get to, but tkae your time and you shouldn't have any trouble.

the other end of the sensor wire is plugged into the control board. In order to get to it, remove the screws from the top plastic cover. They're located on the back of the unit, if I remember there are just 2. The foam insulation is a bit hard to break free, but once you pry the top cover off you should see where the sensor plugs in. I'd recommend testing before you button everything back up, just to make sure.

Hope this helps!