From the tech sheet...
F26 = Door Switch Error
If the door has not been opened for 3 consecutive cycles or the door switch is open while the door is locked for more than 5 seconds.
￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼￼■ Door not opened during 3 consecutive cycles.
1. Open and close the door.
2. Verify CCU operating by running a Diagnostic test or any cycle.
■ Door switch open while door is locked.
1. Push the door and check if it completely closed.
2. Verify CCU operation by running a Diagnostic Test or any cycle.
3. Check door switch contacts.
4. The resistance of both door coils (between pin 1 and 3) should be approx. 320 Ω.http://appliancejunk.com/forums/index.php?topic=12164.0