Mark

The provided print shows the wiring and plug are already installed.
The wires have identifying numbers along with the plug having a equipment list number.
All of that "has" been installed unless a engineering order or documented change has been accomplished.

Provision or "provisions for" added equipment that has not been installed.

If a customer or airline wants to add the extra equipment, the wiring is already installed.

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.
  
     


 

From  CHOXON 2 CHOXOFF

  
 

Procedure to pull up fault history on a RT-910 T2CAS processor.

From ACSS Maintenance Manual 34-43-23

Self−Test Function

By momentarily pushing the TEST switch on the front panel of the TCAS Computer
Unit, maintenance personnel can display fault data for the current and preceding
flight legs. When TEST is initially activated, all annunciators (pass/fail lamps on front
of unit) are ON for a 3−second lamp test, then current fault data is displayed for 10
seconds. If no further activations of the TEST switch are made, the LRU display
cycle is terminated at the end of the 10−second fault display period, and all
annunciators are extinguished.


If during the 10−second fault display period, the TEST button is activated again, the
fault display period is aborted, a 2−second lamp test cycle is done, and the fault data
recorded for the preceding flight leg is displayed for 10 seconds. This procedure can
be repeated up to 10 times to obtain recorded data from the previous 10 flight legs.
If the TEST button is not activated again during the fault display period, the fault
display cycle is terminated at the end of the 10−second fault display period and all
annunciators are extinguished. If an attempt is made to display fault data for the
preceding flight leg when the tenth preceding flight leg fault data is displayed, all
annunciators flash for a 3−second period at a 2.5−Hz rate, after which all
annunciators are extinguished.


When less than 10 flight legs have been flown since the TCAS Computer Unit was
shop tested and recertified, less than 10 previous flight legs of recorded fault data
may be available for display. In this case, if an attempt is made to display fault data
for the preceding flight leg when the earliest flight leg is displayed, all annunciators
flash for 3 seconds at a 2.5−Hz rate and then all annunciators are extinguished.
The TCAS PASS and TCAS FAIL annunciators indicate the status of the TCAS
Computer Unit only. All other annunciators reflect the condition of the respective
sub−system. During troubleshooting, the TCAS Computer should not be removed if
the TCAS PASS lamp is on.

(The "RA DISP" fault in this video was caused by the Inertial Reference Systems not being aligned.)
  
  

From: Old Broken Wrench
  
Coax Connector Lookup in the Boeing SWPM
     
From SixtoSix

How to find a splice part number to repair a wire on Boeing aircraft.
  
     

  

So.... the aircraft is loaded and crew in cockpit. You're called out for a intermittently failing Left Radio Altimeter indication. Cockpit full of mechanics looking for some sort of deferral to move the aircraft.

Rainy as hell for 4 days straight. A visual on the transmit and receive antennas revealed droplets and a water sheen covering the whole face of both.

A rag..... a wipe of both..... problem solved.

The images below are not the problem ones, but it can bee seen that signal interference is possible.

Radio altimeters transmit from 4275MHz to 4325Mhz. Water will definitely cause issues at these higher frequencies.
  
     
     
 

Sealing plugs don't really do much inside the pressure vessel. Especially, up front in the electronics compartment where there should be little to no water or hydraulic fluid.

We plug the holes that don't have wires, but they aren't needed for safe operation of an aircraft.

If I change a plug with ten unused pins, but they only supplied five plastic plugs.... I'll install what I've got and move on. 

Those are plastic sealing plugs to keep liquids out. They are installed at the rear of the plug in the pins slots that are not used.
  
     
 

You have 12 wires with two ends each... 12 more pins are required. I don't know if that's Boeing's job or the individual carrier, but they have to be there to complete the job.