The scene behind the screens

[rodsmith]

Pictures of my wiring job. It didn't turn out as neat as I had hoped, but then I had never wired an airplane before. I found it's hard to herd wires along the same path without a few strays getting away. My biggest advise is where there are connectors, leave plenty of space for the wiring bundle. I was guilty of putting equipment too close together. I ended up having to move the aux alternator controller due to this issue which required splicing some wires. Some of my service loops are probably larger than they need to be. My electrical system architecture was heavily influenced by Bob Nuckoll's excellent book and email group. Because I have dual electronic ignitions, I went with a dual bus, two alternators and two batteries. I'm sure the Light Speed ignititions will work well but if starting now I would use one of the mag replacement ignitions like PMAG.. I waited for years for their 6 cylinder version to be available, finally decided it was vaporware and moved on. The Light Speed ignitions just take up too much real estate with the control boxes, coils and wiring. I never could have accomplished this with the boot cowl in place. I did not have the foresight to fabricate the boot cowl with removable panels. There will be quite a bit of access behind the panel by removing the 10" screens. I left plenty of slack in their connections to easily remove and disconnect them.

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[svyolo]

Wiring was a big job. I have a great deal of DC wiring experience, but never wired a whole "vehicle". Turning the Master on the 1st time for the smoke check was pretty satisfying.

[rodsmith]

I totally agree the satisfying experience of powering everything up. I have some map lights that wouldn't light up even though they had when I initially checked them by applying power to the switch terminal. Was happy to realize that I had forgotten to install the fuse.

[svyolo]

I had my two electric fuel pumps power leads switched, and a warning light wired wrong. But no smoke. I was afraid I would have to buy some Lucas Wiring Harness Replacement Smoke.

[rodsmith]

After completing the harness I decided I should go back and double check everything even though it required reopening connectors. It took a few hours, I found 3 mistakes. A couple pins in the wrong place and two 3 conductor wires wired to the wrong connectors for the audio panel that has two connectors. Would have caused a lot of trouble shooting to find the problem after the fact.

[FFTravism]

Good Job. Looks good.

[500AGL]

So a word of advice to all builders when completing the wiring.

A good avionics shop practice is to ring out a harness on the bench by someone other than the guy that wired it. Then install it in the aircraft, connect powers and grounds, and do a power/ground ring out.

The idea here is to establish that power is only going to the appropriate pins, and no where else. It’s one thing to have a 232 line mis-pinned and it’s another to have 12vdc going to the wrong socket. Fast way to smoke a unit.

To accomplish this without “breakout cables” isn’t too hard, but requires patience and time.

Typically the backplate for each unit is complete, either with or without the tray. You need to fabricate an insulated probe of appropriate length to slide over an individual pin, or into a socket without fear of contacting any other pins or shorting to ground.
A straightforward way to do this is cut a length of welding rod to the size needed. Using a couple of environmental splices crimp on a pin on one end and a socket sized for your multimeter probe on the other end. Do the same for one using a socket on the end sized for your pins.

Now heat shrink the entire Rod and ends to insulate jt from any other contact.
You now have a probe extension for your meter to do ring outs.

On the wiring bench we use highlighters to record the process. On whatever wiring diagram or connector pin out sheet you are using, use one color to signify it was pinned into a connector. Then, when the second guy rings it out on the bench it gets marked with a different highlighter showing it was tested good.

Now using that same wiring plan on the aircraft, and with the previous long ends terminated, you can do a power off and power on ring out and mark the sheet with the third color. Remember to ring out with nothing connected on any end.

Test the power pins _and_ all other pins for No Power.
Test grounds are correct as well.

Shouldn’t be a need to test data lines as those were done prior to installation in the aircraft.

Establishing a program such as this should ensure you have a trouble free panel power on.

[500AGL]

PS. Don’t skip using an insulated probe. You may think you’re good enough to touch only one pin at a time with your meter, but your not.

[rodsmith]

Very true!