Fridge starts and runs for about 8 seconds.

Your fridge is no longer working and you need to buy a new fridge.

Sounds like the limit . Jump out the limit and see what it does

Fridge FAN CONTINUALLY STAYS ON OR SHUTS OFF WHEN DOOR IS OPENED:

NORMALLY WHEN THIS HAPPENS U EITHER HAVE A DOOR CONTINUALLY OPEN ISSUE OR A BAD DOOR SEAL LETTING AIR IN AND CAUSING FAN TO OVERWORK ITSELF. ANOTHER CAUSE CAN BE DIRTY COILS AND CONDENSER AND LASTLY NOT TO COMMON IS A SHORT IN THE FAN SYSTEM ITSELF. A MORE PROBABLE CAUSE COULD BE BAD THERMISTORS OR EVEN COLD CONTROL THERMOSTAT ( WHEN THE THERMISTORS OR THERMOSTAT DO NOT GET/GIVE A PROPER READING, THEY CAN CAUSE THE FAN TO CONTINUE TO OPERATE AS THEY FAIL TO RECOGNIZE OR REGULATE THE PROPER TEMPERATURE.

This sounds like the start winding is trying, and the run winding is not. Check all capacitors. Check to make sure the wires are solidly on the compressor. Check the klixon switch, it should have continuity.

What is the complete model number of the unit?

Seems that the compressor has some fault within the unit as it takes in more current under pressure. Sometimes it can be due to fault within the compressor, failure of the valve , O-rings. Now shut down the fridge for about 6 hours and then plug in the fridge to start. Observe cooling to happen in about one hour and ice to from under three hours.
Earlier make sure that the thermostat was set to normal mode for freezer and fridge. If there is no ice formation we have a big issue as the compressor and gas must be checked out. , if RPM of motor is low check capacitor.
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Please check this link for tips :

http://www.espares.co.uk/advice/fridges-and-freezers/a/2

You refrigerator was made by Frigidaire Adaptive Defrost Controls Frigidaire Refrigerator Trouble Shooting and Diagnosing
On the initial plugin, or when power is restored to the fridge after a power outage:
If terminating thermostat is open, the fridge enters a compressor (cooling) cycle.
If the terminating thermostat is closed, the first defrost cycle occurs 1 hour
after initial plug-in.
Maximum defrost cycle time is 24 minutes.
Minimum time between defrost cycles is 6 hours. (compressor runtime)
Maximum normal clock time between defrost cycles is 12 hours.
Maximum time between defrost cycles (in "vacation" mode) is 72 hours.
Vacation mode is not entered unless the door has not been opened in at least 24 hours.
Note that the ADC will only enter the defrost mode if the terminating thermostat is closed. If the terminating thermostat is open when defrost is initiated, the ADC board will wait for six minutes and then return to the cooling mode.
ASSUMING that the fridge has been on and running,
and the terminating thermostat is closed,
defrost is initiated by pressing the door (light) switch
at least five times within six seconds.
The defrost heater should start heating up within 8 seconds.
If the above procedure caused the heater to heat up, the ADC board is probably bad; replace it.
If the defrost heater does not heat up, test the defrost heater, terminating thermostat and cold control for continuity as follows:
Unplug the fridge from the wall. Unplug the ADC board from its connector.
Test the connector for continuity between the following leads:
Defrost Heater = DEF TERM (blue) to DEF OUT (brown).
Terminating Thermostat = DEF TERM (blue) to NEUTRAL (lt blue).
Cold Control = COLD CONTROL (orange) to L1 (black).
Replace the defective component.

You may have a serious issue with the wiring harness inside the refrigerator.  You will need to have the technician come back out and check the continuity of the wires leading from the control board to the fan checked out.  If there is no continuity, it is not repairable.

main stat? what is a main stat?... do you mean thermostat?...that is the thing that controls the compressor to stop if its already cold inside the compartment. or your compressor could have been hot wired already. has anyone repaired your ref before?