Panel wiring harness complete

Continuing the main wiring harness surgery, I remapped the fuse block wires from what SteinAir originally did - eliminating a few more wires from the conduit to the overhead console (e.g. no reason to have separate wires and fuses for the front and rear overhead lights), and adding the Spartan3 AFR sensor (which I kept on the main bus instead of the Bus Manager on purpose - I only want it to start heating the sensor after the engine is running, and it has a mode where it'll start 3 minutes after being powered on, so on my start checklist, turning on the main bus is the last step before hitting the starter (and before that the avionics are powered by the IBBS, while the EFII system is completely independent of the main bus):

Changes to be made to the fuse block wiring

Updated fuse block and wiring

For connecting the door relays, I got connectors that attach together, and wired them directly from the fuse block:

Door indicator relays attached to sockets

Door indicator relay sockets with power wiring

I then chose the position to attach those relays (nutplates will be added later), and laced those wires:

Fuse block, door indicator relays and GAD29 in place, with wire bundle tidied up

I protected the main bus bar (that connects the tailcone solenoids) against accidental contact with heatshrink:

Tailcone bus bar with heat shrink protecting non-contact areas

I also rewired the EDS-4IP's distributors per MH's recommendation, which means a single power wire pair for all of them (the controller's pins are connected together anyway, and all my distributors are near one another, so that saves me a bunch of wiring up to the overhead console:

Updated Mountain High EDS-4IP connection diagram

For the Spartan 3 air-fuel ratio sensor, I soldered a Molex Ultra-Fit (172287-2308) connector to the board - the connector is only 8 pins (vs the original 10), but the last 2 pins are not used anyway. This will be much more secure than the original screw-in connector, and as mentioned on the last post I'll 3D print a custom case for it:

Spartan 3 AFR sensor with Molex connector soldered on

I then moved the main harness back onto the panel to figure out its attachment - with Adel clamps on the VP-X screw holes on the left, and figured out the right places to add holes/nutplates for Adel clamps on the right:

Tidied-up GTN/GNX wire bundle, ready for re-lacing

Right-side main wire harness held in place with Adel clamps

I attached and wired the essential bus bar and fuel pump relay to the back of the panel substrate:

Essential bus bar connected to circuit breakers and fuel pump relay

I then decided I didn't like this :) The wires going all the way down to the relay felt weird, so I swapped the relay and the bus bar locations, whch looked much cleaner:

Essential bus bar connected to circuit breakers and fuel pump relay, but swapped positions

Finally, I re-laced the main wire harness, which gave it a nice and secure finish (I'll also add some edge grommet to the subpanel hole to protect it):

Re-laced GTN/GNX wire bundle going through subpanel (still without edge grommet)

Re-laced GTN/GNX wire bundle

Re-laced main wire harness

The only part of the panel wiring that I'm leaving for later are the EFII wiring (since I don't have the LRUs yet) and the breakout connectors. There's also of course the rest of the wiring that's not behind the panel (back to the tailcone, in the tunnel, and firewall forward).

Time lapse:


Total avionics rivets: 59
Total avionics time: 76.3h

Panel assembly and more wiring surgery


I riveted the VP-X attachment extension, then attached the essential bus bar to the panel substrate, right next to where the circuit breakers sit:

Essential bus bar attached to panel substrate

Continuing with the wire harness surgery, I was worried about having enough space for all the wires and cables in the conduit to the overhead console. The Mountain High EDS-4IP (oxygen system) had four 4-wire shielded cables which was kinda bulky, but 2 wires in each of those were power and ground, so I checked in with them and they told me it's fine to run a single power and ground unshielded pair to all of them (since they'll be in the same general area), so I took all of those out and will replace them with four 2-wire shielded cables which seems a lot easier to fit. On the cable to the tank valve, SteinAir also hadn't run a wire for the regulator pressure sensor (controller pin 20 to valve pin 8), so I reused one of the 4-wire cables to do that (replacing the previous 3-wire they used for the tank valve):

Reworking the Mountain High tank valve and distributor wires

I wired the battery fault LEDs, by adding Molex SL connectors (so they can be easily removed from the panel, and splicing the main harness wire that went from the GEA24 to the batteries to connect those:

Battery fault LEDs with Molex SL connectors attached

Battery fault wires attached in place

Last but not least, of the 4 wire bundles that connect to the GEA24, 3 (J241, J243, J244) have some or all wires that need to go into the main harness, so I bundled them all into a single harness and routed the wires to the right exit point, while also adding the EFII connections (RPM, fuel flow, fuel pressure, AFR) and removing an unnecessary Molex connector between the bundles:

GEA24 bundle including most of the J243 and J244 connector wires

(J242 only connects to the engine sensors, so I kept that one separate, and also left other wires that will go into the engine compartment outside the bundle)

Next I need to rework the fuse block wires, and then I can finally mount the bundle into the panel again, this time figuring out attachment points and re-doing the lacing (though there are still a few details/wires to figure out, like what I'll do about yaw trim). I can also probably start running the side wire bundles in the airplane (and adjusting/trimming their sleeving since they'll be mostly inside conduits).

Time lapse:


Total avionics rivets: 59
Total avionics time: 55.5h

Wire bundle surgery, power wires and LRU nutplates

Lots of wiring harness surgery...I kinda wish I hadn't paid Stein for hand lacing since I'm having to remove/redo so much of it...

To re-consolidate the VP-X wire bundles (move all wires that should go into the main bundle into it, and move all the wingtip wires out the side the same way), I had to de-pin the Molex 150L connector, which was quite annoying to do, at least with the pin that Stein provided:

Removing VP-X connector pin using SteinAir-provided pin tool

I then got the official Molex tool, and unsurprisingly, it easily removed the remaining pins - the tip was just slightly rounder than the one from Stein, which did the trick:

Molex MX150L pin removal tools - SteinAir-provided (white) and Molex official (black)

I also moved the stick grip and flap wires into the tunnel bundle for simplicity:

Tunnel wire bundle

(Also, did you know that Spruce sells heat shrink by the 4ft piece, and not by the foot? Guess who didn't realize it when ordering and will now have a ton of leftover heat shrink? 😄)

For the EFII's AFR sensor, I got the Spartan 3 which seems to be good in terms of firmware and sensor, but I wasn't happy with the connector they use for power and data (screwed-in wires, specifically a OSTTE100104) so I chose a Molex connector with the same pitch but with a latch (172287-2308), and redesigned the case to fit it:

Spartan 3 AFR controller in original box, without original connector (left) and replacement connector (right)

AFR box model with connector and board

Center section of the AFR box

I also tried a right-angle connector, but ultimately didn't see a reason to use that:

Right-angle connector version of the AFR box

I'll eventually 3D print that (probably PC+CF filament?).

I received my main battery cables from Aircraft Specialty, and they actually fit as intended (caveat that they use white wires and only color the heatshrink, but the terminations are really high quality which makes it worth it):

Box of wires from Aircraft Specialty

(mock) battery, contactors and external power port with wires near their intended spots

(mock) battery and contactors with wires near their intended spots

After a batch of primer, I riveted all the LRU attachment nutplates, to the tailcone avionics tray and the subpanel:

Tailcone avionics tray with LRU attachment nutplates

Subpanel parts with LRU attachment nutplates

I also riveted the VP-X attachment parts:

Riveted VP-X attachment hinge and bracket with nutplates

Coming up next: more wiring work, need to check/complete the GEA24 discrete inputs, rework the fuse block wires (I consolidated a few that go up to the overhead console, added the AFR sensor, etc.), connecting the trim position and ELT wires to the side breakpoint connectors, and simplify a lot of the O2 wiring (MH told me it's OK to run a single power wire to all the overhead distributors, so I'll do that instead of having 4 shielded sets).

Time lapse:


Total avionics rivets: 49
Total avionics time: 45.2h

Avionics mounting and wiring progress

I managed to measure the battery cable lengths I need, and those are on order from Aircraft Specialty. I also drilled nutplate holes for all the subpanel LRUs.

I fabricated the smaller tailcone avionics shelf (mentioned in the previous post) and drilled it for the GTS800 horizontal mount and the WX-500:

WX-500 (left) and GTS800 (right) mounts on the new tailcone avionics shelf

For the GTR20, I'm gonna have a modified version of the F-10112-R made to mount it on the side.

Stein had routed the stick wires to each side (adding splices near the LRU connectors), so I removed the splices and re-routed the wires to the center so I can have a single wire going down the center console and into the tunnel, where I'll install CPCs to attach the sticks. I'll later do the same for the flap wires.

Stick grip wires coming out of the ~center part of the harness

They also hadn't wired the GSB15 to the avionics dimmer bus, so I spliced the wire going to the PFD and added that connection:

PFD dimmer wire stripped at the center

Splice on the dimmer wire (not horrible for a first attempt)

GSB15 connector with dimmer wire

I also removed the WX-500 "display clear" and "COM inhibit" wires from the main wire bundle - I have no use for the display clear connection, and COM inhibit is only needed if I see interference from the COM radio (at which point I can just plug it back in).

Finally, I added Molex SL connectors to the reversionary switch and to the cowl flaps switch so I can remove the front panel without having to unscrew those from the panel:

Molex SL connector on the reversionary switch wires

Molex SL connector on cowl flap wires

I still have quite a bit more surgery to do to the wire harness. Specifically:
  • Add all the VP-X wires that need to go aft to the main harness 
  • Move the taxi light wire from the VP-X J8 to the J10 connector so all lights are coming from the same side of the VP-X (easier to route)
  • Splice all the light wires so they can go out to both wings (and probably with the correct color wire, rather than all red)
  • Connect the door sensor wires
  • Connect the battery fault LEDs
  • Move flap motor and position wires into the center bundle
  • Redo most of the fuse block wiring
  • Move ELT wires into one of the breakout connectors (GTS?)
  • Add the wing root breakout connectors
  • Route the trim position wires into breakout connectors
  • Connect alternator switch wires
  • Add the AFR input to the GEA24
  • Connect the LED strip properly
Time lapse:


Total avionics time: 34.4h

Battery and contactor mounting

I attached the two battery boxes together and to the bellcrank mount:

Battery boxes attached to each other

Battery boxes attached to each other with double-flush rivets, and to the bellcrank mount with flush rivets

Battery boxes attached in place with battery mockup

Battery boxes attached in place with battery mockup

For the contactors, I wanted to extend the OP-48 AHRS support bracket to span both ribs:

Original OP-48 shelf plus a paper extension for taking measurements

It took a bit of measurement and fine-tuning to get the holes in the right positions:

Sketch of the modeled shelf's web with measured hole positions

Rendering of the modeled shelf

Before sending this for fabrication, I 3D printed a thin version of it to confirm the layout:

3D printed shelf model

3D printed shelf model screwed in place

With just a few minor adjustments, I had the part laser-cut and CNC-bent in aluminum, and it fit pretty well:

Aluminum shelf screwed in place

Only exception was that the aft flange was too far aft (I tried to adjust both flanges slightly to not make the fit so tight as it was before, but clearly I adjusted too much, so I had to make a shim:

Shim for making aft flange of the shelf flush with the bulkhead

For connecting the 3 contactors (one for each battery and one for external power), I used a copper bar, which also held them in relative position for match-drilling the attachment holes into the shelf:

Copper bar with 5/16" holes for contactors

Contactors connected by copper bar, holding relative position

Contactors with attachment holes match-drilled in place

Last but not least, I cut a smaller right-side shelf for the GTS800 and WX500 (which I'll post about on my next avionics update).

Next on section 10 is just priming these parts, installing nutplates, and final-installing the relays and batteries in place.

Time lapse:


Total tailcone rivets: 1882
Total tailcone time: 238.6h