Mark

Leach relay P/N BACR13CJ2 causing a cycling "FLAP/SLAT ELEC" warning on the lower EICAS display.
  
  
This is different from the posts above because this one has a 115 VAC coil. All previous intermittent relays were direct current.
  
  
This particular one was failed for about 90 seconds and energized around 10. (I wouldn't have caught it if I wasn't looking at the EICAS screens for another reason.)

When failed the message was in view.

I pulled the relay and checked for power (X1) and ground (X2). These inputs never dropped off. I then jumped the 115VAC and a separate hard ground to the removed relay. It dropped off within 10-15 seconds after power was applied.

A new relay fixed the problem.

In the schematic below, the EICAS computers do not want to see a ground on "F3" of the "D" plug. If a ground is present..... the warning will display.
K730 has 115 VAC available all the time. It's looking for a ground to energize. That ground comes from the Flap Slat Electronics Unit on pin "K13" of the "B' plug. If the FSEU is operational, it will provide that ground and there will be no warning present.