Three weeks ago, the freezer section of my Samsung refrigerator (twin cooling) just stopped getting cold. No warning or previous symptoms. No error codes flashing. None coming up during self-diagnostic. The fridge section is also only getting down to 50 degrees. Here's what I've checked so far:
- Set temps: Freezer -2, Fridge 34.
- Actual room temps: Freezer 70, Fridge 55.
- No icing on the evap coils.
- All temp thermistors tested accurate.
- All fans tested fine.
- Condenser coils clean, and fan working.
- 115V present on SMPS PCB. DC170 found at BD1 rectifier (good).
- 12V and 5V outputs on SMPS PCB good.
- Front panel seems to operate normally.
- Test mode works as it should. As does demo mode.
- Tried resetting several times and left unplugged for a couple hours. No change.
- Compressor starts fine. No unusual noises.
- No continuity when testing start relay (DA35-00103B, PTC thermistor). Relay resistance tested very high - 1.2K ohms at room temp.
- OLP tested fine.
- Run cap tested fine.
- The compressor also stops running before reaching set temps. This could be due to OLP kicking in.

Q. So, how is the compressor starting with a failed start relay?
Q. Could a failed start relay cause the compressor to start but not cool the unit effectively?

Thank you, WilliamM. There is no frost pattern on the freezer evap, and it is only cool to the touch. Freezer temp and defrost sensors were removed from the unit and resistance tested correct for both at room temp and in a freezing slurry. Their resistance was also correct when reinstalled and tested at the PCB with the wire harness pulled. Their voltage tested correct at PCB - connector and at MICOM.

I will remove the fridge cover and check frost pattern there. Do you think it's necessary to remove the fridge thermistors and check their resistance? I did check their resistance and voltage at the PCB, as well as the ambient thermistor, and all checked out fine.

I'm puzzled. If the start relay (PTC thermistor) is not failed, why can't I read continuity when testing (no beep), and why would its resistance read 1.25k ohms?

The compressor does shut off, but not because the unit has reached its set temps. I'm not sure how long it runs before shutting off, but it is hours. This happened on June 10 and hasn't changed since. By the way, the OLP resistance is 0.3 ohms.

Thanks for your help with this.