My refrigerator Model #59672383411 Kenmore bottom-mount refrigerator. Refrigerator section will not go below 40 Degrees

[Russ B]

My refrigerator model number is Model #59672383411 Kenmore bottom-mount refrigerator. It is a dual evaporator unit. The refrigerator temperature is 40-41 degrees, the freezer temp is 0 degrees . The refrigerator temperature setting is 33 degrees (low as it will go), the refrigerator temp and air coming out of the tower is now 39 degrees. It is interesting in that the air temperature coming out of the tower is 27 degrees when the refrigerator starts cooling.. After about 4 minutes it is 37 degrees. I have removed an looked at the tower, no obstructions. I thought the evap cover might be causing a leak around the fan but it seals.. The air seems to moving well. ..  Any possibility the closed system 3 way switch between the freezer and ref evaporator coils might not being opened completely?  Or that there may be an obstruction in the freon line on the refrigerator evaporator coil side?

PLEASE HELP

[Rhubarb Tau]

Air temp at the air tower isn't a great indicator of cooling performance, because it's subject to the temp of air that's being drawn into the evaporator. With the doors open, it'll draw in warm air and discharge temps will climb. 

A better indication is the frost pattern on the evaporator.  Inspecting the Evap will also show if excessive frost is preventing normal air circulation through the evap. 

I haven't seen many issues with the switching valves on these units, or many issues with restrictions on units that haven't previously been worked on. If the evaporator is bare aluminum (not painted black), it is an older style, which was redesigned (black painted evap) to minimize the possibility of pinhole leaks in the evaporator.

[Russ B]

Thank for the response, I would agree the temp coming out of the tower is effected by the door being open.. But the temp is lower when the cooling cycle kicks on not after it has been running going from 27 to 37 degrees in  4-5 minutes.. If I can add a picture I will show you the frost pattern, but it is not icing up at all.. Nope don't know how to add a picture..

 

[Russ B]

By the way the evap coil is black..

[Rhubarb Tau]

3 hours ago, Russ B said:

If I can add a picture

I think without a professional membership you would need to upload the picture to a hosting site like Dropbox, Imgur or Google Drive and post the link to that page here.

Looking at frost patterns, we're looking for an even coating of frost over most or all of the evap. If there's an iceball on the inlet, or the first few inches or turns have frost but rest of the coil is bare, it can be an indication of an issue with the sealed system.

[Russ B]

Here is a pic of the evaporator coil

https://spacecoast.craigslist.org/art/d/refrigerator-cooling-coil/6754135610.html

 

It is a craigslist listing but the picture is the Ref evaporator coil.. It was taken with the cover off..

[Rhubarb Tau]

That's a pretty good looking frost pattern. I'd say that points away from leak or compressor, ; the unit is mechanically  capable of cooling. It might be a switching valve issue, but fwiw I've worked on a lot of these units, and haven't run into a valve issue. Other techs might have different experience?

I'd test the Ref. cabinet sensor (you might find a tech sheet under the right ref hinge cap or behind the toe-kick), and take a close look at the FF evap fan, might be running intermittently.

[Russ B]

Thanks for the response,

After discussing the problem with a local A/C guy (for about half and hour)  he suggested the symptoms could point to the control board slowing down the compressor speed after the sensor (clipped to the ref evaporator coil lead) starts sending info back to the control board. And since I had replaced that sensor the control board might be incorrectly reading  information from the sensor, which would explain when starting the compressor is at full speed the temperature at the tower would be 27 and then when it received the info from the sensor and incorrectly reads it, it slows down the compressor producing only enough freon flow to be 37 degrees. His suggestion was to temporarily remove the sensor from the evap coil and see if the compressor runs fasted by monitoring the current (amperage)  to the compressor.

What do you think?

Have a great Turkey day,

[Russ B]

After a discussion with a appliance guy the said the sensor that is clipped to the evaporator coil is to turn on or off the defrost function but  the ref. temperature sensor (which has also been replaced).. The same condition could be the issue that the control bard is misreading the ref. temperature sensor and slowing down the speed of the compressor after it starts.. That causing the tower air temperature to go from 27 to 37 in a few minutes.. 

What do you think?

[Rhubarb Tau]

Sensor or Control Board issues are pretty rare, but it could be; difficult to diagnose without throwing parts at it. Do you hear the compressor slowing down when the temps rise?

I'd focus on the basics and take advantage of the fact that you have more time to spend studying the unit's behavior than a repair guy does when he's in the home. Try powering the unit down for 5 min., plug it back in and listen and take notes on what you hear. Does the compressor start within a few minutes? Does it continue running? It's normal for the compressor to slow down after it starts. Is the Ref. fan running consistently?

I'd rule out the more common failures before replacing the Control Board.

[Russ B]

I can monitor the compressor control voltage with a volt meter.. Do you know the compressor control voltage output pins from the control board (W10589837)? Or the other board W10453401? There are two other boards under the control board Not sure what they control..

[Russ B]

Found out that the board s below the control board is the inverter control board (W103060786) would the two output pins be the leads to the control the compressor speed?

[Russ B]

I didn't answer your earlier question the fan shuts sown when the ref. evaporator coil goes off or switches..

[Rhubarb Tau]

The two other boards on the back of the unit are power supplies, but they don't drive the compressor. One is a DC power supply for the controls, the other is a supply for the LED lighting.

The inverter that drives the compressor is a grey box in the compressor compartment. It receives 120VAC and a DC control signal from the main control board that sets compressor speed. The control signal output on the main control board is P8-7 (Red) and P8-8 (Blk). You'll need a meter that can measure frequency for a useful measurement. 55Hz is minimum compressor speed, ~150 Hz is maximum speed.

[Russ B]

I read there was a DC input to the grey box from the control board was supposed to be from 0 to 6 volts DC, is there  such a output?

[Rhubarb Tau]

That's the same Ctrl board output that I mentioned above. Manufacturers using this Embraco inverter commonly call this a variable DC signal voltage, but that's not entirely accurate. The desired speed is signalled to the inverter by the frequency of a DC square wave. Depending on how the Mfg implemented this (the duty cycle of the signal) and the multimeter used (true RMS or averaging), you'll get different DC voltage readings. 

The inverter is looking at the frequency of the signal. Any change in the overall DC voltage reading is just a side effect and not an accurate measurement (despite what the mfg states).

[Russ B]

OK I understand, I am an Air Force trained electronic tech.. So now I have to have is a freq meter or an O-scope.. Nothing is ever easy..

[Russ B]

found a cheap frequency meter do you happen to know what frequencies the signal from the control board operate at?

[Russ B]

this unit says from 10 cps to 10 megs.

[Rhubarb Tau]

8 hours ago, Rhubarb Tau said:

55Hz is minimum compressor speed, ~150 Hz is maximum speed.

 

[Russ B]

Thank you, you have been very helpful and I hope I have not caused you to waste your time but I have learned a lot.. I will be getting the meter to monitor the frequency of the control board and will send the results in a few days..

Again thank you,

Russ

[Russ B]

Well here is some data from a sensor (located next to the Ref Temp sensor) to look at,

Time  - Temp -  Compressor -  Speed 
2:22    41    On    low
2:28    38    On    low
2:34    41    On    low
2:53    42.8    On    low
3:29    41.7    On    low
3:51    43.9    On    low
5:05    40.6    On    low
6:06    41.5    On    low
6:23    41.5    On    low
6:55    41.9    On    Fast
7:02    39.9    Off    
7:08    41    Off    
7:10    40.3    Off    
7:33    38.7    On    low
7:43    40.3    On    low
7:55    41.4    On    low
8:08    39.4    Off    
8:20    41    Off    
8:31    40.5    On    low
9:23    40.3    Off    

Looks like the compressor only ran fast at the highest temp recorded 41.9 and the temperature goes from 38 degrees to 43.9 at the ref temp sensor.

Also looks like the unit is operating correctly only at the wrong temperature should be oscillating around 33 degrees rather than 41..

 

Any Ideas?
 

[Russ B]

That was a dumb statement, the compressor only ran fast at 41.9 degrees and it was NOT the highest temperature..

Sorry..

[Russ B]

One more piece of information.. I purchased the control board and installed it ...  It made no difference the temp near the ref temp sensor is at the same temperatures that it was before I changed the control board..

Boo Hooo I am crying...

[Rhubarb Tau]

Yep, as I mentioned earlier, control failures are pretty rare. It seems like you've narrowed it down to the Ref. temp sensor. Have you checked that yet against specs?

I would first measure the sensor resistance (at a known temperature) at the control board with the connector disconnected. If there's a bad connection somewhere along the line, you want to catch it in the act before you disturb it