New actuator question, I think

I have read extensively on F-chat about actuator problems and diagnoses. I cannot find anywhere that someone has had a similar problem to mine, so here goes. Light was intermittent, now constant. Both front and right rear rotate during system check, but left rear does not. Switched a front (rotating, and apparently working) with the rear left. Guess what, no rotation in left rear on start up, but front (former rear left) did while attached to front wiring. No apparent corrosion anywhere on back left electrical, sprayed and cleaned connection, still no rotation. Is this a problem with the wire leading to actuator, or could it be something with the actuator ECU. Thanks for any help or suggestions.

 

OK, I'll try that, thanks. Does anyone know if there is a second connection point between the actuator and the ECU, or is it one cable running the whole length. I looked on Ricambi and could not find a diagram of those wires.