The aircraft had come to the hanger for planned maintenance, on this aircraft there was a fire detection loop problem that needed to be fixed. My colleague started on that job and I started on another job that was in the technical logbook.
A reed switch had been found to be faulty, our colleagues at the line maintenance had troubleshooted the defect and they had ordered a new switch.
This switch turns the power on for the fuelling system of the aircraft when u open the fuelling panel, if this switch doesn't work there is a manual overide that needs to be pressed in order to power the fuelling system but ofcourse we prefer the switch to be working.

So I get started by getting the right tools for the job and setting up the steps and the parts needed.
this is the fuelling panel
This is the fuelling control panel.

The power should be on when the panel is opened but it doesn't work.
no power on the fuelling control panel

This is the switch that causes the defect, a reed switch is a magnetically operated switch. the target that moves with the door is a magnet, as soon as this magnet comes close enough to the reed switch the contact inside the switch closes completing a circuit and power should be applied to the fuelling control panel.
the reed switch

Here's the new switch, straight from the box.
the new reed switch

As i take the old switch out, it's evident that it's been in the airplane for a while. One of the screws turns out to be corroded.
removing the switch

Once again, I have little or no access to get the wires out.
no access

Because I have so little access space, instead of crimping new pins on the wire and insert them into the connector I decide to splice the wires onto the original wiring.
wire splices

In this case I use awg 16-18 waterproof splices.
blue splices

I make myself some more space.
disconnect for access

I temporarilly splice the new switch.
temporary splice

And then I splice the new switch onto the wires of the old switch.
temporary splices

With these temporary splices I can pull the new wiring through the P-clips without disconnecting them. This saves me a good couple of hours work.
new switch connected to wiring

Then I pull the wiring through the P-clips and cut out the wiring that I don't need.
wire in place

I put the shrinksleeves over the wire, do this BEFORE u crimp the splices into the wire, it took me quite some trial and error before this was common practise.
(and sometimes I still forget).
crimp sleeves in position

Then we can crimp the wire splices onto the wires.
wire splices crimped

Then I put the shrinksleeves over the wire splices and after this I'll shrink the sleeves with a heat gun making the wire repair watertight.
wire splice finished

The wires are now spliced, I put them back into the wire loom and tie the loom back together with tie laces. I reconnect the connectors to their receptacle's and install the new reed switch with new screws (the old ones were corroded).
installed

Proper tie lacing makes a wire loom rigid and easily routeable.
tie lacing

As u can see, the power is back onto the fueling control panel, the new switch works as it should.
power onto the fuelling control panel

I close off by testing the panel and the systems that were affected by the connectors that had been disconnected. This job is now complete.