As I noted in my last post, the installation of the GIB headrest components and the wiring took a bit longer than I had anticipated.

I’ll digress for a bit and discuss this morning’s EAA meeting, where I was regaling my fellow members of my painting adventures over breakfast.  I reiterated a number of times one of my primary mantras: It’s better to be lucky than good.

My frustration the night before last leading into all day yesterday was a missing ground wire that I had made up (back in 2018) for the SD-8 backup alternator’s self-excitation feature, which is not quite as racy as it sounds.  It means that the backup alternator can come online even if the battery is completely dead, something a normal alternator cannot do.  Now clearly a 6″ 20 ga ground wire with a Fast-On connector on one end, and a D-sub pin on the other is something I could gin up in 5 minutes and move on with my life.  However, this one happened to include a very specific 3K 3 watt resister spliced in line.  And of course there was the nagging question of simply, “where the hell did it go?” [you can see a new replacement black ground wire hanging out of the G6 ground buss awaiting a resistor]

Ahh, but life in general, and this build specifically, has a strange way of leading you to a better understanding of things, and thus it came to be in “the case of the missing SD-8 ground wire.”

You see, after digging back into the AeroElectric Connection book to verify I had everything hooked up correctly, I then spent a good hour and a half on the forum to ensure there wasn’t any specific intel that I had missed… and there was.  It turns out that the probability of needing a self-excitation feature is relatively low, and that Bob Nuckolls eventually began to eliminate this feature from his latest system diagrams.

Moreover, there was mixed results on the inclusion of the self-excitation feature, with it working great for some builders, and not so great for others.  This strongly suggested possible installation issues on some builders’ parts and/or implementation issues with other specific system architectures.  Nonetheless, I now know there may be some gremlins hiding in the shadows when it comes to incorporating and using this self-excitation feature.

I will still install it as Bob Nuckolls designed it, but with my eye on either rolling the SD-8 install back specifically as prescribed in the B&C install instructions, or to a unique circuit design used by some RV bubbas.  Only ops testing will bear out what eventual path I’ll take on this, and given I’ve captured the data for either alternative options, I think all is good on this and I’m pressing on with other component installs/wiring.

One final note is that for the added self-excitation feature, including the $6 I just spent to order another few 3K 3w resistors to replace the one I lost (no doubt I’ll find the original one in the next week or two!), I’ve got less than a whopping $40 in these extra parts.  So nothing gut-wrenching about eliminating the feature if it doesn’t work.

But I am happy to report, that besides that little nagging detail, and of course the crazy numbers of iterations and creative cable & component management I had to employ to get everything to fit into the headrest, it is finished and hopefully will be all good when I go live with the power!

Pressing forward . . .