RT18AKXK009 - After a power outage the refrigerator will only run on the highest #. If turned down it shuts off & will not go back on.

Correct, it sounds like the power supply onboard is coming up then sensing an issue and shutting down.
Power supply circuits are quite sensitive to surges, brownouts, which humans cannot "see" normally

Sounds like you had a power outage?-- did the lights go dim for a few minutes, before the power actually went out?-- Sometimes, low voltage will cause the compressor motor to over heat-- so it might have to 'cool down'-- What happened next?-- Did you try it again an hour or so later/-- Tell us more-- Mack B

We have a solution to this link that will help

http://www.fixya.com/support/r6019270-refrigerator_freezer_air_conditioner

Try this link it should help http://appliancehelponline.com/refertopevapfan.html

do a full manual defrost then turn unit on and let it settle for 24 hours then check temp guage.....(try to keep doors shut when settling down)

The power outage is suspected to corrupt the RAM. Get in touch with the vendow and get it replaced.

Pressing the power freeze and power cool buttons at the same time for 8 seconds to get start

This is the best way to tell. If your system is shutting down on you by behaving like your shutting it down thru windows then it could be a spyware, virus trojan issue going on. If thats the case then run your virus program and see what it finds and remove it. If your laptop is shutting down on you where everything turns off right away with no lights, kind of like a power outage then go ahead and remove the battery and only use the ac adapter and see if that solves the problem. If it does solve the problem then you know its your battery that is the culprit. If your only using the ac adapter and the machine shuts off on you like a power outage with no lights then you know its a problem with the motherboard. With just the ac adapter plugged in, wiggle the cord near where it plugs into the laptop and if it shuts off on you like a power outage then you know its a loose DC Jack and it needs to be resoldered back into place. Hope all this helps.

If you have a blocked capillary tube that had nothing to do with a power outage. You could get this if the condenser got EXTREMELY dirty. The cap tube runs up through the wall this is true but I have run external line sets up the back wall to bypass this sort of problem. You have to know where to drill so as not to hit the old line set or the electrical wiring which is also in the wall.