GE psc25 fridge coil frosting solid

[jaffadog]

Hello - I'm having trouble with my GE Profile PSC25MSWCSS side-by-side refrig.  This unit has a single compressor and 2 evaporators (freezer + fridge).  There is a defrost heater on the freezer evap, but not the fridge evap.  I'm having trouble with the fridge evap totally frosting over to the point where there is no airflow - then fridge temps start to rise.  The freezer coils seem to do ok.  I've confirmed the defrost heater functions - by manually triggering it in the diagnostics.  I've checked out the thermistor resistances - and they all seem ok (they pass diagnostics too).  One troubleshooting diagram suggested replacing the main board when you have this situation (when thermisters and heater coil check out OK).  I've replaced the board, but still seem to be having this heavy frost problem on the refrig side.  One thing I've noticed is that the refrig evap cover, which is a shaped foam piece with plastic skin, seems to be heavy - like its absorbed moisture - and probably no longer much of an insulator.  I'm still wondering how the refrig evap coil is supposed to get adequate defrost.  I'm also thinking there must be a solinoid that controls refrigerant delivery to the refrig coil - how likely is that sort of failure?

I'm wondering what I should try next. Ideas?

Thanks,
Jeremy 

[theoldstoveguy]

Refrigerator defrost is done by the fan running AFTER the unit has met temperature in the fresh food section. Just completed a service school over the last 4 days.The most common problem was the thermistor mounted to the evaporator, even when they had a normal reading. That thermistor was causing a number of related problems with frost in icemaker areas and things you wouldn't even think were related. They said to make sure you get it tight when you mount it to the evaporator.

[jaffadog]

well that's interesting!  The thermister on the fresh food evap coil is mounted in an aluminium block (maybe 2"x2"x1") which is then wire-tied to the evap coil... right into the metal bristly mess.  This differs from the freezer coil thermister, which is clipped directly to a clear piece of tubing at the top of the coil bundle.  The fresh food coil  bu comparison does not have a "Clear" portion of tubing to afix the thermister to.

[theoldstoveguy]

Does the fan continue to run after it has met temperature? That is the first thing to check. After the fresh food thermistor ( on the walls) is satisfied ,the valve will shut off the refrigerant to the fresh food evaporator. The fan will run at low speed until the thermistor mounted on the evaporator is satisfied at 35 degrees. If the fan turns off too soon, it will frost up. Changing it is not that easy.

[jaffadog]

I'll have to check the fridge fan once it reaches set point.  I just put it back together this afternoon and its at 4/44 now... I've turned turbo cool on to try and accelerate it to set point.  I've had the fridge fan out - it's mounted in the foam evap cover.  I'm considering replacing that covering, as it appears to have absorbed a lot of moisture (its now "heavy" foam) and may be contributing to the fridge evap frosting. 


The part can be had here and includes the fan, part # WR60X10184 


I also took the custom cool box apart last night to check the damper doors (that was a royal pain) - they're working fine.  I never actually use the custom cool settings - so these damper doors should just remain shut all the time.  thanks for the info on the fridge fan logic.  I might try move that fridge evap coil thermister to get it in direct contact with the tubing.  That thermister is the only one that I noted was a little off when I tested it in ice water - but it was reading ~17kohms - on the cold side of actual.  I can't figure how a slightly colder reading could contribute to frosting.

[jaffadog]

One other question... when I ran the 0/2 diagnostic (temp control to main board comms) it displayed "61 14" persistently, and never went to "P".  I don't have any documentation of what the actual tests and expected reponses are for this model - so I'm not sure if this is an actual fault or not.  Can anyone reference the proper service manual?  thanks!

[theoldstoveguy]

I have a paper manual nothing on computer. Thermistor should read @ 32 degrees 16.3k ohms @ 41 reads 12.7k ohms. Nothing about 61 14 reading, sounds like temperature settings. I would say thermistor on the refrigerator evaporator. There is a whole page of how to install  it,not easy. 

[AJ]

Just added...

31-9153 GE Profile Side-By-Side Refrigerators Service Manual

[theoldstoveguy]

I knew if I asked "THE BOSS" he would figure a way for me to get it to you. Hope that helps.

[jaffadog]

Wow! you guys are aces!  thanks for the upload - looks like I have some bed time reading to do.

[jaffadog]

Just closing this out..... I replaced the thermister on the fresh food evap coil, and no longer seem to have icing issues on that coil.  All is back to normal.  Thanks for all the help!

[whirlpooltech]

Just closing this out..... I replaced the thermister on the fresh food evap coil, and no longer seem to have icing issues on that coil.  All is back to normal.  Thanks for all the help!

Got a part number for that thermistor?

[jaffadog]

Got a part number for that thermistor?

I used a GE WR55X10025. The original part has a slightly different rubber molding on the wire at the thermister - a right angle and some rubber ribs designed to hold it in the aluminium block.  But the part i bought is electrically identical - produces the current resistance for a given temperature - and I just used a dab of silicone to hold it in the block.


GE WR55X10025 Temperature Sensor, AP3185407

[theoldstoveguy]

Good to hear it worked, time well spent in that class. I am too old to learn a new trade so had to learn the new stuff. Paid off many times already,You can teach an old dog new tricks. But he may not remember them for long.