Ok, electrical is my thing... just don't ask me to go within 1000 yds of a wig wag washing machine. I'll run away screaming like a little girl.
This thread is suffering from "overcomplicating the simple" syndrome.
The thermostat return side, evap fan motor hot side, condenser fan motor hot side and motor overload hot side are all the same electrical point. If you lose one you lose them all unless what you're dealing with is a crappy wiring connection.
If you lose it at the thermostat then you'll lose compressor, condenser and evap as a matched set. They'll all go down together. As I understand the description, this is NOT what's happening.
Don't get caught up in worrying about the compressor turning off and the unit defrosting (as in heater making sizzling sounds). This is a normal, good thing. If it defrosts for hours and hours and your food gets warm then that's not so good but you didn't specify which it was in your description. Since you said everything magically came back on I'm going to take a leap of faith here and hope that what you saw was a normal defrost cycle.
Don't get distracted (SQUIRREL!!!!!) by the fact that there was a thin, even coat of frost on the coils. You have no idea how many refrigerators wish they were running well enough to have that coating be like a thin, even coat of paint. It's a sign that the cooling system is operating not well, but perfectly... it also has absolutely nothing to do with the problem at hand.
If you lose the evap motor but the condenser and compressor are still running then we can draw some conclusions:
- Your thermostat is fine. If it wasn't then neither the condenser fan motor nor the compressor would be able to run at all.
- The defrost timer is in normal run mode, not defrost mode. If it went into or got stuck in defrost mode then, again, you'd have no condenser fan motor or compressor action.
This, my dear Watson, leaves us with the evap fan motor and it's associated wiring... and the motor is new.
You said that you tested the voltage at the fan motor before your replaced it and that voltage was good, while the old motor didn't work. Here is the big money question:
When you tested the voltage at the evap fan motor you tested the power coming into it on the red wire but where did you put your other meter lead?
Did you put it on the white wire right there as close to the evap fan motor as possible or did you ground your other lead by touching it to some piece of metal on the cabinet of the fridge?
- If you have no motor action but the motor is good then it has to be an issue with power in OR the return path.
- If the voltage is shared with other things and they work, the voltage supply is fine.
- This leaves us with a wiring issue between the voltage supply (thermostat) and the evap fan motor OR between the evap fan motor and Neutral.
This means that you have to carefully check for voltage between the cabinet metal and the white wire at the evap fan motor while it's plugged in and the condenser motor is running. You need to see if that 120VAC supplied to the motor is showing up on the white wire side of that motor, indicating a "bad ground".
If, during this check, your 120VAC is in and out (when measured at the RED wire) while the condenser motor is running just fine then this means you have a wiring issue between the thermostat and the evap fan motor but it's in a place where it doesn't affect the connection between the thermostat and the condenser fan motor.
Short version: High probability that the connector you plug the motor into has a bad connection on one side or the other. Be sure to do your checks on the evap motor side of the connector so that you're checking the connector itself. Don't get tunnel visioned thinking it has to be an issue with the power side (red)... a bad connection on the white (ground or return) side will kill it just as dead and is a lot easier to overlook.
That's all there is to it. See how simple that is?!?
Edited by Vets Appliance, 07 May 2013 - 11:55 AM.