A couple of weeks ago my whole fridge randomly quit on me. It wasn't that the fridge warmed up first and then the freezer a couple of days later; it was just both at once. I got back behind the fridge and removed the long metal backing at the bottom to expose the fan and compressor. The long cylindrical fan was caked in dust which I shop vac'ed out the best I could. The fridge has been off for about 2 weeks now so the evaporator coils are definitely defrosted! I noticed when I plug in the fridge the fan at the bottom kicks on but I get nothing from the compressor; no humming, no vibrations, no heat, nothing. The compressor just doesn't kick on. I took off the compressor relay and checked it for continuity and it is fine. I even second guessed myself and ordered a brand new relay and installed it and still the compressor does not kick on. I took off the cover for the motherboard and it looks fine, no little resistors broken off, no scoring marks on the motherboard, looks completely normal. So to summarize:

• Side by side fridge and freezer warmed up at the same time; no cooling at all.
  
• All lights work in the fridge as does a fan. When I open the door there is air blowing; its just warm humid air!
  
• The fan in the long cylindrical canister under the fridge runs when fridge is plugged in; cleaned out dust the best I could
  
• Fridge has been off for a couple weeks now so all frost is gone; nothing covering the evaporator coils.
  
• Motherboard looks good, no visible damage
  
• Compressor is not kicking on when fridge is plugged in; no hum, no heat, no vibration. Relay tested and was ok but replaced to be sure; no improvement.

Can anyone let me know what the problem might be?? It it does end up being the motherboard that is fine and I can pay the $130 to buy a new one, but if the compressor is done it's new fridge time! I just hate to have to call someone out and pay them $150 just to tell me it's new fridge time. I'm pretty handy but I've never really worked on appliances. If it's an easy to moderate fix I'll be fine though!

Thanks!

I looked over the whole motherboard again extremely close and couldn't find any loose solder joints. I have not removed the motherboard from the fridge yet. When you say the bottom are you referring to the bottom of the side of the motherboard with all the wires and transistors or take out the motherboard and check the underside?