FIXED GE Monogram Side By Side (ZISS420DMD) – Evaporator keeps freezing over

[brettcp]

Model Number

ZISS420DMD

Brand

GE

Age

More than 10 years

I have a GE Monogram Side By Side (ZISS420DMD). Last month I noticed the freezer was at -8 and the refrigerator was up to +45. I found that the freezer evaporator was completely frozen over (a solid block of ice). I thought that maybe one of the doors possibly didn’t get completely shut overnight, so I unplugged and defrosted overnight until it was all clear and dry. Powered back on, after 4-5 days, same issue occurred. I then replaced the items in the list noted below, and everything was perfect for about three weeks after these items were replaced.. I thought I had the issue resolved, but then today the freezer was at -14 and refrigerator at +44... sure enough the evaporator has again completely frozen over again.

Here’s my journey so far:

Ran the following diagnostics:

• 0-2: Communication check between control board and main board: Pass
• 0-3: Communication check between temperature control and dispenser: Pass
• 0-4: Communication check between dispenser and main control board: Pass
• 0-7: Control and Sensor System Self-Test (Checks each thermistor): All Pass
• 1-0: Dampers test: Pass. I can hear each damper move during this test, also ran this test with physical access inside the dampers and they are opening/closing as expected.
• 1-4: Defrost test: Pass. This does kick on the defrost heater as expected, and the heater does in fact get hot.

I’ve tested the following via a multi-meter:

• Defrost heater. I’ve disconnected it and do get continuity between both leads.
• Evaporator thermostat – I tested this by disconnecting it, putting it into a glass of ice water with a multi-meter connected and it does in fact close/open at its specified temperatures.
• Thermistors (at the control board wiring) – The resistance does seem to change along with the temperature of each thermistor.

I’ve replaced the following (with all genuine GE parts):

• Main control board (WR55X11130) Note: Every multi-meter based test I could find online passed with my existing control board, but I replaced this anyway.
• Run Capacitor (WR55X24065)
• Compressor Relay (WR07X10055) Note: I did find that the old relay was in fact bad (it was rattling, and I found that the ceramic disc inside was broken into a dozen shattered pieces). I initially thought I’d found the issue here!
• Compressor Overload (WR08X10025)
• Both door gaskets. I did find that the original gaskets had a couple small tears at the bottom, and weren’t completely flush/seal in a couple areas using the dollar bill test. New gaskets seal perfect.

Additional notes:

• The fan inside the freezer does kick on when the doors are shut, and seems to kick on frequently throughout the day.
• I have NOT yet tested the “Refrigerator defrost bi-metal thermostat” (WR50X10035) as it seems to be difficult to access.
• The condenser fan kicks on throughout the day as expected and runs at full speed. I’d previously replaced this fan/motor due to it becoming noisy and slow (probably 6 years ago), but seems fine now.
• It seems that I can manually run the defrost cycle a handful of times to melt the iced evaporator and the temperatures will work their way back to normal. This leads me to believe its something with the defrost cycle? Is it possible that the Evaporator thermostat is getting intermittently "stuck" which causes the heater to not kick on as often as it should?

At this point I’ve learned more than I ever thought I’d know about refrigerators, but apparently still don’t know enough to have this figured out! I’m a stubborn one and try to DIY as much as possible and would really like to figure out the culprit here. Any input would be greatly appreciated.

Thank you in advance!

 

[brettcp]

After defrosting, this morning I disassembled the upper freezer/evaporator area and tested the freezer evap thermistor, it consistently tests 18.1k omhs @ 32F. I ended up testing all thermistors in the unit (all left in a glass of ice water measured exactly at 32F and let sit for 5 minutes before measuring). All were measured at the wiring connector at the mainboard (disconnected from mainboard):

FF Evap: 15.15k
FF: 14.8k
FZ Evap: 18.1k
FZ: 16.2k

I've previously read that at 32F the reading should be 16.2k and not vary by any more than 5%. The FZ Evap is off by 11%. Is it reasonable to believe this could be the cause of my issue? Thermistors are fairly cheap so if these readings are cause for concern, I may as well just replace them all at once.

Also - at room temperature, the FZ Evap thermistor reads 8.6k omhs, while all the others read 7.3k ohms.

 

[brettcp]

I replaced all 5 thermistors this morning (2 in the freezer, 2 in the fridge, and the 1 for the quick chill section) and now all 5 are providing consistent resistance readings at the connectors at the control board. It may be a few weeks before I know if the issue is resolved.

If anybody has any feedback/suggestions in the mean time, please feel free to share.

Thanks!

 

[Jake]

It seems you've done everything right. Your defrost heater ohms good, and the control board is making the making the defrost heater come on, so it must of been the evaporator thermistor, that was too far out of range.

Yes, normal for the evaporator thermistor is about 16.3k ohms when its in a glass of ice water for at least 5 minutes.

Thermistor WR55X10025


Hopefully the new evaporator thermistor fixed it.

 

[brettcp]

Thank you, @Jake - I appreciate your reply! I'm hoping the new thermistors do the trick, but I think I'm at the point where if its not fixed, I'll probably call in a pro. Will give it a few weeks to see what happens and will update this post. Thanks again!

 

[Jake]

Yes I agree, if the new evaporator thermistor does not fix it, contact GE at 1-800-432-2737 to have a GE tech. come out to see what's going on.

 

[brettcp]

25 days and counting - still good. No ice build up on the evaporator and temps are consistently 0 and 37, sometimes fluctuate a couple degrees but work themselves back to 0 and 37.

 

[Jake]

Excellent, glad to hear that.

Thanks for the update!