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Amana SRD25S5W: warm with intermittent cool, but not cold
My 11 year-old Amana SRD25S5W refrigerator stopped cooling a couple of months ago. It's warm for the most part, with intermittent cool, but not ice cold. Armed with component specs, assembly drawings, schematic, and wiring diagram, I spent the last month trouble-shooting it on and off, with many hours learning about refrigeration systems from the Internet. Here's what I found:
The compressor, rated at 1.6A underfull load, starts at 2-3A, then drops to 0.8A steady state. Frost starts to form on the evap coils at the entrance to the coils only. After 3-5 minutes, the frost starts to melt while the compressor continues to run under full voltage (120VAC). However, the compressor current now drops to 0.5A. The fridge is confirmed not in defrost cycle, as the defrost heater is cold.
Occasionally and randomly, the frost starts to form again at the evap coils entrance for no reason (current increases to 0.8A), then melt again after a few minutes. All of these happen with the compressor running continuously cool to the touch. 120VAC measured at the C terminal of the compresor (after the overload circuit breaker) at all time.
The sound from the compressor is normal, same with that I hear from other fridges. It starts and runs with or without the PTC relay connected (I removed the relay and use jumpers to bypass it). This is very strange because I thought the PTC relay is needed to start the compressor. In my case, the compressor starts and runs fine with just the 15uF run cap connecting between the start windings (compressor S terminal) and L2 (AC neutral). When I remove the run cap and leave the S terminal open, the compressor doesn't start. Current draw under that condition is around 12A as expected.
The evap fan, condenser fan, overload ckt breaker, run capacitor, adaptive defrost control board, adaptive defrost all work properly. The condenser is relatively clean. PTC relay is solid (doesn't rattle when shaked), looks new, and seems to work. It's barely warm when running with the compressor. The PTC relay for some reason does not make any difference here. The resistance checks out OK (5.6 Ohms at room temp, specs is 3-12 Ohms). I test it on the bench with a 100W light bulb. The bulb does go off after a while, once the PTC relay is warm. The resistance increases with high current passing through, and decreases during cool down when current is removed. So PTC relay seems to function OK.
What could be wrong here? Thank you very much in advance for any comments.
The compressor, rated at 1.6A underfull load, starts at 2-3A, then drops to 0.8A steady state. Frost starts to form on the evap coils at the entrance to the coils only. After 3-5 minutes, the frost starts to melt while the compressor continues to run under full voltage (120VAC). However, the compressor current now drops to 0.5A. The fridge is confirmed not in defrost cycle, as the defrost heater is cold.
Occasionally and randomly, the frost starts to form again at the evap coils entrance for no reason (current increases to 0.8A), then melt again after a few minutes. All of these happen with the compressor running continuously cool to the touch. 120VAC measured at the C terminal of the compresor (after the overload circuit breaker) at all time.
The sound from the compressor is normal, same with that I hear from other fridges. It starts and runs with or without the PTC relay connected (I removed the relay and use jumpers to bypass it). This is very strange because I thought the PTC relay is needed to start the compressor. In my case, the compressor starts and runs fine with just the 15uF run cap connecting between the start windings (compressor S terminal) and L2 (AC neutral). When I remove the run cap and leave the S terminal open, the compressor doesn't start. Current draw under that condition is around 12A as expected.
The evap fan, condenser fan, overload ckt breaker, run capacitor, adaptive defrost control board, adaptive defrost all work properly. The condenser is relatively clean. PTC relay is solid (doesn't rattle when shaked), looks new, and seems to work. It's barely warm when running with the compressor. The PTC relay for some reason does not make any difference here. The resistance checks out OK (5.6 Ohms at room temp, specs is 3-12 Ohms). I test it on the bench with a 100W light bulb. The bulb does go off after a while, once the PTC relay is warm. The resistance increases with high current passing through, and decreases during cool down when current is removed. So PTC relay seems to function OK.
What could be wrong here? Thank you very much in advance for any comments.
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