ELCU

There are no circuit breakers for the four electric hydraulic pumps (one each for left and right, two for the center). Power control is accomplished by use of a ELCU (Electrical Load Control Unit).
  
     
  
The ELCU (which I would classify as a "contactor"  because of the heavy current load) is activated by a switch in the cockpit. It has a internal CT (current transformer) circuit that looks for a phase imbalance between the three power wires that feed the pump.
  
     
  
I didn't take a video..... but this thing is fast. We had a pump with a shorted power wire. I initially thought the ELCU was bad as I had no output with the switch on. I was wrong. You have to have a meter on one of he output wires while someone throws the switch in the cockpit. I had 115VAC for about a half second before the thing tripped.

The only way to verify the the ELCU is bad is by taking the power plug off the pump. Excluding a short in the wires..... if 115VAC isn't seen on the output terminals, you've got a bad ELCU.

For safety reasons, I would pull "the big breaker" (external power) before changing this thing. Those upper power input wires could cause you to have a very bad day if you touched them with power on the aircraft.