Leach Relay P/N BACR13CF2A

Leach relays are used extensively on all Boeing, Airbus, Douglas, and Gulfstream aircraft. They can be found in numerous other types of corporate aircraft.

They are extremely reliable as they can last numerous decades with thousands of cycles.

Years ago, I encountered a relay from a Gulfstream that was acting like the car blinkers of old. The coil would get hot and go open which caused the relay to relax. As soon as the coil cooled, it would energize again.

rotate.aero/forum/relays-general/79-leac...and-closes-from-heat

In my short few months on the 767 I have found "two" examples of the same fault.

rotate.aero/forum/ata24-767/314-ata-24-3...ilure-indication#564

rotate.aero/forum/767-ata27/304-ata-27-62-auto-speedbrakes

Both have had the same part number BACR13CF2A.

In defense of Leach, both of the recently failed relays were quite old (as noted by the pitted "feel" of the case).

Another one......

You can't hear it click over the equipment cooling noise, but the repetition was every few seconds.

Thanks!

Another relay acting like a car blinker.

This time for the right wing anti-ice valve disagree warning.

The relay must be energized to keep the warning from view, so it spends most of its life engaged.

Activated relays get HOT, which causes higher failure rates.
   A suitable substitute, part number BACR13CF2AB can be used as a replacement.
  
     
 

Another one.... (longer duration of 6 minutes this time).

This one controlled the Manifold Interconnect Valve for the forward equipment cooling system.
     
     
  
Approximately every six minutes we get a "Valve" light on the cooling control panel and a "Fwd Eqpt Valve" message on EICAS.

We had to isolate this one with engines running. 30 minutes and a 1000lbs later..... we found it.

Please reference  rotate.aero/forum/767-21cooling/380-ata-21-58-equipment-cooling   for more information on troubleshooting these types of messages.
  

    
  
We tested the bad relay on a power supply after removal.
  
     


 

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.