FIXED ZISS420DRJSS GE Monogram side by side built-in doesn't hold temperature

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sungpark

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Model: GE Monogram ZISS420DRKSS

I'm having the same problem with the original poster. I think the evaporator coil frost buildup is causing temperature rise on both refrigerator/freezer sections. Replaced both motherboard & inverter board and still having issues. How do I access & check evaporator coil area to check thermistor and defrost heater? The previous poster (Aaron_Portland) stated resistance values for defrost heater and thermistor. How do I check those values?

Any helps are greatly appreciated. Thank you.
 

sungpark

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rickgburton,

Thank you so much for the fast response.

With power on, J7-J9 current: 0 Amp. I expected this since defrost heater is never turns on.
With power off, J9 blue connector to J7-9 resistance: Reading open circuit. NOT getting 18-20 ohms.

Is this mean defrost heater is bad and needs replacement? For my model (ZISS420DRKSS), is it possible to force the defrost cycle? I want to make sure defrost heater is the culprit.

In the post #6, you were showing how to remove panels to access to evaporator coil. How hard is to replace defrost heater? One I get the access, I should replace the thermistor as well. Any other parts I should replace that affects the frost buildup? I'll remove the panel tomorrow morning to check the frost condition.

Any other suggestions are greatly appreciated. Thank you.
 

sungpark

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Rick,

I have some more questions for you if you don't mind:

1. With power off, J9 blue connector to J7-9 pin resistance: Reading open circuit. NOT getting 18-20 ohms.
However, if I get J9 blue connector to the J7-9 CONNECTOR side resistance, I'm getting 38 ohms. Diagram in your post #22, do I tap my multi-meter probe to J7-9 pin side or connector side? Don't I expect to read open circuit on the pin side?
2. Also, I checked the evaporator thermistor resistance reading from J1-4 to J1-5 connector side ~16 kohms.
3. Defrost heater for my refrigerator seems very hard to replace and expensive. Have you seen them going bad often on GE monogram models?
4. I'm in the process of taking apart my freezer side. I'm in the step to remove styrofoam insulation and noticed everything (evaporator and drain pan) is completely frozen. I'm waiting to get melted out to safely remove styrofoam.

Thank you.
 

rickgburton

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do I tap my multi-meter probe to J7-9 pin side or connector side?
I'll have to fix that in my diagram. Leave the J7 connector connected to the board and go in through the back of the connector on J7-9.

I checked the evaporator thermistor resistance reading from J1-4 to J1-5 connector side ~16 kohms.
Hmm....was the power off very long when you measured the resistance of the evaporator thermistor? The evaporator thermistor is also used to terminate the defrost cycle. When the machine is cooling the evaporator temperature is about 20° colder than the air temperature and can be as low as -25°F to -30°F and even lower just before the defrost cycle in "pre-chill"
Prechill.jpeg


16KΩ = +32°F so if the machine was unplugged for a while that might be correct. Here's a GE thermistor temperature/resistance chart:
011 GE Thermistor Chart.jpeg
 

rickgburton

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sungpark said:
Rick,

Sorry about keep asking questions, but I need your help. GE monogram refrigerator (ZISS420DRKSS), your post #6 on 'Thread: FIXED: ZISS420DRJSS GE Monogram side by side built-in doesn't hold temperature', I'm in step 9. I don't see drain hose clamp. Drain hose connector is covered with adhesives. How do I remove the drain pan without breaking it? Once removed, will I be able to access defrost heater and thermostat?

Really appreciate your help.
Sung
It's easier for me if you just ask your questions here instead of PM. Try to remove the adhesive if there's no clamp. Lower the left side and pull.
 

sungpark

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Rick, happy new year.

I couldn't completely remove the drain pan, but was able to move it to access evaporator coil areas. Removed defrost thermostat and checked continuity. It's reading ~1 ohm at room temperature. Is this correct? I did some research on this thermostat, unlike others, it only opens when gets hot. The evaporator coil area is so tight, defrost heater and thermistor, I don't even see them. How do I access, even replace them if needed?

While taking the freezer section apart yesterday morning, I noticed heavy ice buildup in the drain pan area (thus blocking drain hose with ice), and had to wait til evening to remove styrofoam and drain pan. Couldn't check the frost pattern. Also, I noticed drain pan has heating elements. Could this cause the problem?

Another concern is the motherboard. I bought an open box unit, but confirmed it is tested working. Should I try a brand new motherboard?

I'm running out of ideas and about to give up. Any helps are great.
Thank you.
 

sungpark

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My defrost thermostat is stamped L65-20F.

Above 65F: open circuit
Below 65-20 = 45F: 1~2 ohm
Between 45~65F: 1~2 ohm

I was hoping to replace the thermostat, but this unit seems to be ok.

What else should I check?
 

sungpark

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As I stated, my defrost thermostat is reading slightly above 1 ohm temperature below 65F, then becomes open circuit above 65F. My multi-meter is a dirt cheap one, which may not be accurate. What is the spec value? Is above 1 ohm means faulty thermostat?
 

rickgburton

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sungpark

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Rick,

I'm getting closer to find the frost buildup root cause. I think the reason defrost thermostat is reading above 1 ohm is because of my cheap multi-meter. I will try to use fluke meter at work to get exact resistance reading.

As I stated in post #28, in the process of removing freezer section, I noticed very heavy ice buildup in the drain pan area, and noticed heater element at the bottom of the pan, which I suspect it's not working.

Here's the part: https://www.appliancepartspros.com/ge-icing-kit-wr49x10021-ap2636547.html

Is there a way to check the drain pan heater resistance through one of motherboard connectors? I highly suspect this is the culprit. I gave up accessing/replacing defrost heater, but drain pan heater element changes can be done I hope.

As always, your help is greatly appreciated. Thank you.
 

rickgburton

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J12 - J7-9 is the drain pan heater. You're making this a lot harder that it needs to be. If the defrost heater is not turning on, as you already stated, the problem is either the defrost thermostat, the defrost heater or the motherboard. It has to be one of those three components. As I already stated, if you read an open circuit between between J9 and J7-9, the problem is either the defrost heater or defrost thermostat.
 

sungpark

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Rick,

I took some break from my refrigerator troubleshooting, but have not given up yet.

I might have given you wrong information in my previous post, mainly because I wasn't sure what I was doing, but let me summarize what I have done/tested so far:
-Defrost thermostat (L65-20F): Open circuit above 65F, and showing continuity below 65F. The unit checks out OK.
-Defrost heater: J9 blue connector to J7-9 connector side: 38 ohm. The unit checks out OK.
-Drain pan heater: Removed the unit and the resistance is reading ~330 ohm. I thought this was the culprit, so purchased a new unit, but reading the same resistance. Do you know the correct resistance reading?
-Cleaned out drain line. It was somewhat blocked with curd, but not completely.

I put back together turned on the unit today. I have not installed a new drain pan heater yet, since it's reading the same resistance as my original unit. I will observe if ice is building up in the drain pan again. Any suggestions are greatly appreciated.
Thank you.
 

rickgburton

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OK Let's start over. The drain pan heater is good (330Ω). J12 - J7-9 I marked it on this diagram. It might not be in the exact same location but it's marked J12. Measure the resistance of the evaporator thermistor in the J1 connector. Disconnect the connector and put you meter leads J1-4 and J1-5. A thermistor is a variable resistor that changes value with temperature.

The evaporator temperature can be as low as -30°F or as high as +40°F and the thermistor needs to be checked at a known temperature. Remove the thermistor from the evaporator and let it hang down. Put the thermistor in a small glass of crushed ice and just enough water to cover it. Wait a minute or two then measure the resistance on your meter. At 32°F the thermistor should show 16.3K ohms (16,300Ω).

If the thermistor checks good and the defrost thermostat and heater check good, the board must be bad.

WR55X10560 Board Asm Main Contro


GEMB-03 Defrost Test.jpgGEMB-04 With Inverter.jpg
 

sungpark

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Rick

I ran the my refrigerator for couple of days to check the ice buildup on the drain pan, and sure enough, it started collecting some ice. Measured drain pan heater resistance again at J12 - J7-9, and reading 345 ohm. Is this considered ok, or too high?

Next, I checked the evaporator thermistor reading at J1-4 - J1-5, reading 16 kohm. I measured ~20 to 30 min after unplugged at 0F, so the temperature shouldn't have gone up to 32F yet. I'll leave it unplugged and check the resistance again at room temperature. According to the chart you provided, it should read 6.5 kohm at 65F (post #26).

So, I'm now suspecting evaporator thermistor is not reading the correct temperature. I need your help here. Where is it located for my model? I located the evaporator thermostat, but was not able locate the thermistor. Please help!!!
 

rickgburton

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It should be right next to it. I marked it in this picture. Pull it out of the clip and you'll have enough play in the wires to test it the way I described in my last post.
evap thermistor.jpg

Check it like this if it tests out of range at the board then use a couple wire nuts or black tape to install it. You'll need to cut the wires to replace it.
Thermistor Testing.jpg
 

sungpark

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Thank you so much for the picture. It has been 3-4 hours since unplugged, and still reading 16 kohm. Will check again after reaching room temperature.

For the drain pan heater, is 345 ohm considered within the range, or too high?
 
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