Monthly Archives: March 2023

CAN BUS ERROR!!! OH GAWD!

This entry was posted in Avionics Electrical on by

So a few days ago, I turned on the avionics to find that nothing was communicating. How could this be? It was all working perfectly, and then something happened? At first i thought perhaps I hadn’t trickly charged the batteries enough and a low voltage was causing some LRUs to drop offline. Nope. Speaking with Garmin they told me to disconnect LRUs and reconnect individually to try to identify a bad unit. That didn’t work either. The only other possible culprit – the CAN Bus. So i pulled the connector on the GDU 460 and buzzed it out. I got the appropriate 60 ohms across CAN HI and CAN LO. Which told me that the CAN Bus was contiguous and terminated properly. Perhaps a short to ground? Bingo. CAN LO was buzzing as shorted to ground. Great. Finding that isn’t going to be easy. The only real way to do so, is to divide the CAN BUS in two, and figure which is the bad half, and keep doing that until the offending segment / connector is isolated. So i did that, and found that the bad area was the GMC 507 to GEA24 to GTR20 segment. The GEA 24 is really hard to reach, and is where i had just been cinching wires together. I buzzed it out, and thought i determined taht was the bad connector. Reinstallation of the connector didn’t solve the problem. But i did it from inside the airplane. Which, given the GEA24 is down by the fuel pump… is difficult. I decided to pull both segments out of the plane so i could diagnose and correct on the bench. Long story short, I isolated the leg that was bad. Then tried to determine which connector was bad. Ultimately, even after cutting both ends off the cable, the cable still buzzed as shorted to ground. I completely tore the cable apart and examined everything with a magnifying glass. I was unable to find the offending section.

I built two new segments and reinstalled them in the plane. With all the troubleshooting this was a major time sink, and quite frustrating. But everything is back to 100% functionality. While human error cannot be ruled out, i was extremely meticulous in testing the cable on the bench. I really think there was a flaw in the cable somewhere that was exposed when i began cinching wires with zip ties.

FWF Work. Ignition wires and oil temp sensor.

This entry was posted in Electrical General Electrical on by

I noticed that my oil temp sensor was not torqued, nor safety wired. Ugh. Why did i wait until there was a bunch of other stuff in the way to do this? I set about getting a proper torque on the sensor, adding safety wire, and then connecting the wires. Small projects, but with limited space and access – a major pain in the ass that took way longer than it should.

I also finalized the routing, length and termination of the electro air EI spark plug wires. I’m very happy with how that all turned out.

Lastly there was a ton of work not pictured in routing, organizing, and securing other FWF cables. It takes a lot of time to get the routing correct and everything bundled in such a way as to not rub or interfere. You also must pay close attention to allowing for engine movement. You need some slack between the engine and connections tied to the engine mount or the firewall. But not too much slack!

I will try to get more photos of the wire routing soon.

Magneto Ignition Harness and Prop Safety Wire

This entry was posted in Electrical General Electrical on by

As my engine isn’t exactly standard, i’ve had to modify the ignition harness – because, well I didn’t have one! I bought the experimental one form Aircraft Spruce, but i then had to make it to the bendix plate. This required some experimentation and thought. The harness was originally attached with screws. The new high flex wires won’t allow that to work. The kit supplied by acs has small hollow pop rivets that get crimped onto the ends. The problem is, there is a rubber piece that has to have the wire through first before you can fix the ends on the leads. The end solution was I needed to slice the rubber, attach the cimped ends, and then re-insert. Given the shape of the bendix attachment This should be plenty secure.

I also had to route the ignition leads. I originally had the magneto aircraft plugs on the top of the engine and the autoplugs on the bottom. But, ease of access made this a bad idea. So i had to reverse.

I also safety wired the prop. Which, while painful, isn’t as bad as some folks made it out to be. Granted, there were a couple that I had to redo more than once…