Garmin Can Bus wire - Really $8.85/ft

I have a G5 I will be wiring up (magnetometer and likely a arinc429 adapter).... two questions.

Garmin's recommended $8.85/ft or another less expansive "120 Ohm 24 Awg can bus wire" is $7.50 ft. I can get high quality shielded twisted pair wire for about $1.10/ft. 120 ohm really? Any suggestions?

I got the Garmin G5 used with harness but it was cut with the approved wires. Can I splice it back? I hear it can be done carefully, but it may cause problems. May be better to de-pin and start over. Suggestions?

I have to laugh with magnetometer being a 15 ft run. It would cost over $120 in wire to use Garmin recommended wire.

I am no expert to can bus, but it can't be that picky. I suppose if you have a complicated set-up with a lot of nodes.... Can bus is not new cars have had them for well over 20 yrs. I don't think they are using anything more than twisted pairs.

jackking123 said:

I have a G5 I will be wiring up (magnetometer and likely a arinc429 adapter).... two questions.

Garmin's recommended "120 Ohm 24 Awg can bus wire" is $7.50 / ft. I can get high quality shielded twisted pair wire for about $1.10/ft. 120 ohm really? Any suggestions>

I got the Garmin G5 used with harness but it was cut. Can I splice it back? I hear it can be done carefully, but it may cause problems. May be better to de-pin and start over. Suggestions?

I have to laugh with magnetometer being a 15 ft run. It would cost over $100 in wire to use Garmin recommended wire. I am no expert to can bus, but it can't be that picky. I suppose if you have a complicated set-up with a lot of nodes.... Can bus is not new cars have had them for well over 20 yrs. I don't think they are using anything more than twisted pairs.

Click to expand...

The cheaper stuff works fine.

Garmin says regular shielded twisted pair cable is fine. Anecdotally, everyone I've spoken to has skipped the fancy wire and not had any issues because of it.

Milspec becomes an issue if CAN is over 60' long. Smaller plane with few LRU's probably not an issue. RV-10 with numerous LRU's can easily exceed 60'. Ask me how I know. Wish I'd put Gigaflight in originally. If you need to change out due to bus issues and can't easily replace the entire length, it can be spliced into an existing Milspec bus. Replace long runs first, ie. wing run to roll GSA and possibly GMU 11.

Call Gigaflight directly for much better pricing.

"It would cost over $120 in wire to use Garmin recommended wire."

You sound like the kind of person who would refuse unrequested pin striping, VIN etching, paint protectant, ScotchGuard, undercoating, destination charges, extended warranty and nitrogen-filled tires on a new car. Do you not care if the salesman's kids have shoes, or the espresso machine in the Garmin caffeteria is in tip-top shape?

How dare you.

I have wired the CANBUS on three separate airplanes, an RV-10, RV-8 and Rans S-21. I used the less expensive shielded wire on the two RVs with no problem. The results were much different with the S-21. I also used the less expensive shielded wires on that airplane. The magnetometer in that airplane is mounted in the tail and I’m running more LRUs than I did in the -8. When I began configuring the 21, the system wouldn’t communicate with the GMU11. After multiple telephone calls with Josh at Stein and trying a number of different solutions, we finally decided to begin exchanging the normal shielded wiring with the more expensive MILSPEC wire. Long story short, I had to replace wire at each end of the CANBUS but not the entire system. The replacement solved the problem. So, in fact, the less expensive shielded wire doesn’t always work. Stein sells the MILSPEC wire for $6.25 per foot. Definitely more expensive than standard shielded wire. Consider your lenghts and the complexity of your installation. Take your chances but be prepared to replace the less expensive wire if your system won’t communicate with the LRUs at the ends of your bus.

I ordered directly from Gigaflight last year and paid $3.41/ft for 100 ft.
-Bob

I used Gigaflight and ordered directly from them. One important advantage to me at least. It was 26 gauge wire so instead of splicing in the pigtail you could just combine two wires in the pin itself.

Garmin don't specify high spec wire for any other reason than sometimes cheap wire causes all kinds of problems. Short wiring runs can better tolerate lower quality wire. Figure out the length of your bus, anything over 30' and I would buy the expensive stuff.

Ok a little overkill. Regular tefzel twisted shielded pair works fine in our planes. I dont see a need to spend $500 on special wire for the canbus. JMHO.

I used 26 awg TSP tefzel. Everything fine. The awg is small, so double over the end and us 24 awg setting on pin crip tool. YMMV

22 from Stein is $1.10 and I haven’t had issues.

$8.55/ft reminds me of that landing fee feeling…….

Bill Boyd said:

"It would cost over $120 in wire to use Garmin recommended wire."

You sound like the kind of person who would refuse unrequested pin striping, VIN etching, paint protectant, ScotchGuard, undercoating, destination charges, extended warranty and nitrogen-filled tires on a new car. Do you not care if the salesman's kids have shoes, or the espresso machine in the Garmin caffeteria is in tip-top shape?

How dare you.

Click to expand...

Sounds like a personal comment toward me... and may be not untrue. Ha ha. Yes I spend money like a drunk sailor on shore leave who just got paid sometimes, when it makes sense and is a good value. But mostly wasting money, like doing the same thing for X10 the cost I am Mr. Frugal. Wasting money is against one of my credos. I am not against nitrogen in tires, and. I do care about children BTW. I get free nitrogen fills and give charity to Saint Jude hospital.

I don't give a rip about those automatic espresso machines. Barf. I make my own espresso, grinding fresh dark roast beans, with a (expensive) Italian commercial grade burr grinder, pro espresso machine. Life too short and Espresso too sacred to drink cafeteria swill. Real espresso is made by a barista, me. These extravagant appliances that cost X10 or more from something at Target, will last a lifetime with superior quality, making perfect espresso. I have my grind, weight, extraction volume down to a nano. Ha ha. That is important, but Can Bus wire? Yawn. Will it make my RV faster, lighter, more fun to fly, safer, more efficient? Doubtful at least at $8.85/ft.

It is like Audiophile gear. You can spend $500 on special speaker wire. People do it. "There's a sucker born every minute"; PT Barnum. I respect Garmin and clearly these specs are for the certified TSO and STC world. They try and emulate Honeywell, Sperry, L3Harris, Collins, BAE Systems. You don't find many Garmins in Air Transport and Military aircraft much. I have a good friend who is a retired engineer, worked in military and air liner avionics. He knows all about these specs. CAN BUS by the way is not mil spec or air craft spec. It came from Bosch car world. Now it is open source and all over. Although can bus has made it onto aircraft (B777 cargo loading system which is isolated from main aircraft systems and not flight critical). TSO and Mil Spec standards are great. However overkill in a GA EAB aircraft. The goodness will be from the care of the wire installation. I will give my harness and all wires the attention I give my espresso. Ha ha. The best wire installed poorly is no good. A decent equivalent wire without pedigree installed well is as reliable and long lived. $1.10 wire it is. I think fresh wires and pins is better than splicing any day. What will I do with that $100 savings in wire cost? Buy more coffee beans?

I am a cheapskate (who blows big money at times and understands penny wise pound foolish). "You get what you pay for." This axiom is both true and false. Not always. I save here to spend there. I do get a thrill saving money. My dear departed Mother, was genius at scratching a dollar, a wise consumer. It rubbed off on me. It is fun getting deals. My favorite word? Free! Ha ha. Now down to Radio Shack to get my plane wire... Ha ha.

I used the Gigaflight CANBus wire for my Cherokee. The Garmin install manuals indicate that 22 gauge shielded twisted pair is acceptable UNLESS you are installing their autopilot, then the CANBus wire is required. I only needed 25 feet of wire total, the extra cost for the correct wire was not even a rounding error on the avionics installation. I've spent too many hours chasing down network problems in my business that turned out to be bad wire for me to cheap out on it anymore.

[That is important, but Can Bus wire? Yawn. Will it make my RV faster, lighter, more fun to fly, safer, more efficient?]

Safer? Well depends: if you're a VFR guy it's no big deal if the CAN bus quits, however, pucker factor increases exponentially if you're IFR.

Walt said:

[That is important, but Can Bus wire? Yawn. Will it make my RV faster, lighter, more fun to fly, safer, more efficient?]

Safer? Well depends: if you're a VFR guy it's no big deal if the CAN bus quits, however, pucker factor increases exponentially if you're IFR.

Click to expand...

Just out of curiosity, have you, Walt, or anybody else for that matter, been able to trace CAN bus failure unequivocally to the use of twisted shielded pair rather than the Garmin-recommended wire?

Not trying to be argumentative here but rather trying to understand the magnitude of risk of CAN bus failure related to one type of wire over another.

Canadian_JOY said:

Just out of curiosity, have you, Walt, or anybody else for that matter, been able to trace CAN bus failure unequivocally to the use of twisted shielded pair rather than the Garmin-recommended wire?

Not trying to be argumentative here but rather trying to understand the magnitude of risk of CAN bus failure related to one type of wire over another.

Click to expand...

Yes, absolutely. The longer and more complicated a system gets the more necessary this wire becomes. For short, simple systems the standard milspec wire is probably sufficient; there are thousands of systems flying with this wire. The longer a system gets the more the impedance of the wire matters and there begin to be communication errors in the system. This can be a really insidious issue to deal with as well, since its not a simple pass - fail. The G3X can withstand a certain level of CAN errors, though the threshold is not documented, and there should be none in a properly wired system. If your system is too long, and you are using the milspec wire you might be fine, you might have errors randomly propagate, or you may have units that do not communicate at all with your system. Your system may appear to be functioning perfectly for a while, then you might lose everything for seconds to minutes before it comes back, which could put you in a bad spot if you're in IMC.

If you are wiring a system that is short (say 35 feet) I would not have major concerns about using the standard milspec wire. You can also mix and match this wire with the GigaFlight wire for some increased reliability, especially if you use the Gigaflight wire on long runs such as the servos and magnetometer. If you are wiring a maxed out RV-10 with every option and 66 feet of CAN bus I would HIGHLY recommend using the GigaFlight wire.

For what it's worth, we have had enough CAN bus related communication issues that were related to system length we now use the GigaFlight wire on all Garmin projects regardless of length. This has made a substantial difference.

Canadian_JOY said:

Just out of curiosity, have you, Walt, or anybody else for that matter, been able to trace CAN bus failure unequivocally to the use of twisted shielded pair rather than the Garmin-recommended wire?

Not trying to be argumentative here but rather trying to understand the magnitude of risk of CAN bus failure related to one type of wire over another.

Click to expand...

I have not done a before/after comparison between the 2 wire types, but I can say that I have seen a number of CAN bus issues and a few of them were definitely related to excess mil spec wire coiled up somewhere. I've also seen a plane that was converted from Trutrak to Garmin and the installer elected to just use the existing stranded wire to the old servo as a 'CAN' bus, and it still managed to work okay somehow, a tribute to the robust nature of the bus. Personally, I've used the milspec on numerous installations without issue, but that was before I/we knew better.

I will still use the milspec on 2 seaters, but I am also very careful with routing, connections and keeping lengths to a minimum.
I always use the good stuff on RV10 and RV14's now on the long runs out to the servos/magnetometer but may or may not use the milspec on the panel connections.

Canadian_JOY said:

Just out of curiosity, have you, Walt, or anybody else for that matter, been able to trace CAN bus failure unequivocally to the use of twisted shielded pair rather than the Garmin-recommended wire?

Not trying to be argumentative here but rather trying to understand the magnitude of risk of CAN bus failure related to one type of wire over another.

Click to expand...

Yes I have.

Installed a GHA15 into an existing system that had been operating perfectly for 500hrs. The extra LRU and extra length put the CAN Bus into overload.

Symptoms were intermittent CAN communications. Disconnect the GHA15 and problems disappeared. Replaced GHA-same problem. Found that turning off roll GSA or GMU11 (they were outboard of the GHA with the GMU being the termination) also solved the problem. Repinned GSA & GMU11-same problem. Noticed CAN Bus comm numbers climbing on the GMU11 in the Diagnostic Configuration mode (hold down MENU & NRST while powering up). Found out this is common for a CAN problem to show up at the end of the bus.

Swapped out CAN wire with the 'good stuff' from wingtip (GMU11) to the panel (included roll GSA, GHA15 & GDU 460)---ALL GOOD.

Lesson learned. Milspec twisted/shielded can handle small systems but you need the 'good stuff' for a larger system. I wish I'd used the Gigaglight for the entire system and will for any future system. There is a price for a stable system.

You can read several other comments in previous posts. Just search 'CAN BUS'.

Canadian_JOY said:

Just out of curiosity, have you, Walt, or anybody else for that matter, been able to trace CAN bus failure unequivocally to the use of twisted shielded pair rather than the Garmin-recommended wire?

Not trying to be argumentative here but rather trying to understand the magnitude of risk of CAN bus failure related to one type of wire over another.

Click to expand...

Yes, we are able to very easily observe signal degradation with our test and development equipment. How this kind of problem manifests, varies widely. It can and will lead to serious problems in a G3X Touch/G5 system in complex systems with long CAN bus runs with a lot of CAN LRU's.

In general, the important concepts have been mentioned above. Using impedance matched wire is a useful and necessary tool for maintaining signal integrity as CAN bus complexity grows. CAN bus complexity increases as the overall bus length and/or number of devices connected to the bus increases.

This requirement was derived from many years of implementing, developing, installing and troubleshooting CAN based G3X (Touch) and G5 systems. The original installations were a short databus including 2 displays and a GSU 73. Many LRU's have been added to the bus over the years, and bus lengths have grown, which have spurred different requirements and considerations than in the past.

Thanks,

Justin

Justin

Good info and timely as well- getting ready to start a panel upgrade. Do you happen to know the characteristic impedance of the MIL-C-27500 shielded twisted pair wire? Doesn’t have to be exact, just curious how bad the mismatch is. Thank you- Garmin support is the best.

So out of curiosity, as I'm no where near needing to wire anything up yet. (only have the Emp together so far, and putting off the disassembly for LCP replacements) Which CAN spec is typical for the aviation systems? On the automotive side we design around J1939-17 and -21 mostly.

I can say from experience if you ever do experience a problem because of the wire, after you've spent countless hours trying to fix it you'll wish you had used the right wire from the start after you figure out it's the wire. Given the total cost of building an RV these days, and the relatively small amount of wire needed, it's worth it to use the right wire from the start.

I've been following this thread in the shadows. Great community of experts for sure! The only thing I have to add is..... 10% off CAN WIRE at SteinAir through the end of 2024!

I appreciate this discussion and those who have put some level of quantification on the "problems" associated with using twisted shielded pair vs the GigaFlight wire - thank you for taking the time to provide rational responses to my question.

Walt said:

[That is important, but Can Bus wire? Yawn. Will it make my RV faster, lighter, more fun to fly, safer, more efficient?]

Safer? Well depends: if you're a VFR guy it's no big deal if the CAN bus quits, however, pucker factor increases exponentially if you're IFR.

Click to expand...

I am an ATP and flying IFR for +3 decades in Van's aircraft and large aircraft. You imply that this is dangerous. Please explain. "Pucker factor increases exponentially", is a lot of hyperbolae. Do you have some data? There is no wrong answer. It is up to you.

To you point IFR? If my GPS has loss of communication with Nav display, the Garmin GPS built in display would give course deviation, but loss of LPV vertical guidance. The EFIS has built in full data base and it's own WAAS GPS, with an approach mode option. Not worried.

Frankly single pilot, single engine is solid IMC is already a risk more than wire type. I don't plan on flying in convective weather, at night, over mountains with WX at Mins at departure, en-route, destination. Can bus wire can't help those risks. From my experience as a CFII teaching giving IPC's in GA planes over the years, the weak link is not wire. I do agree IFR is serious business. If you have "pucker factor" flying you are doing it wrong.

This is my conclusion, for EAB (not STC Std Cat aircraft) high quality AIRCRAFT twisted pair shielded is an option that will work satisfactorily for a simple system in my opinion. My opinion is based on research, talking to biggest panel builders, anecdotal declarations by builders who use aircraft wire.

Tipping point from my research on when Can bus is strongly required (in my opinion) is how many Can Bus nodes you have. For me 2. If you have magnetometer, two autopilot servos, control panels, engine instruments, several duplex NAV inputs, dual displays pushing network length, yep Can Bus wire would be the way to go. To argue for expensive Can Bus wire, small plane you should be able to keep the total network length under 20'. What is $190 for wire, when you spend $19,000. Again up to you. People have strong feelings. I am quasi ambivalent on wire. It's a choice I will make. I have samples of both wires in my hand. I can see the difference.

How about if you lose your ADAHRS? Now you're relying on your backup instruments (assuming you have one).
(Don't count on the back RS232 lines to save you as they will only work with a complete CAN failure.)

You're obviously a more experienced and much better pilot than I, but for me losing the PFD and autopilot would be 'exciting', don't think I'll die but would definitely rather avoid it. Can I hand fly an approach with Ipad and G5, yes, but never had to while actually in IFR conditions.

Not sure which RV you are building but assuming a late model with a standard G3X suite, there is no way you could do a CAN bus with 20'.

If I were to bet, it would be that failures are due to the connections/crimps instead of the wire........

Webb said:

If I were to bet, it would be that failures are due to the connections/crimps instead of the wire........

Click to expand...

Agree 100%. Bad crimps are easy to make. Even for those of us who spent 30 years building aerospace harnesses. I have over 600 teeminations in my G3X suite, probably 10% being canbus. I took care to test every crimp. Yet when I was done, my friend was inspecting the harness and found 3 canbus terminations with bad crimps, even thou network errors were reported as zero. If he had not found those, I would suspect I would be seeing can bus failures by now and wondering how I repair a bad crimp buried behind the panel…….

PilotjohnS said:

Agree 100%. Bad crimps are easy to make. Even for those of us who spent 30 years building aerospace harnesses. I have over 600 teeminations in my G3X suite, probably 10% being canbus. I took care to test every crimp. Yet when I was done, my friend was inspecting the harness and found 3 canbus terminations with bad crimps, even thou network errors were reported as zero. If he had not found those, I would suspect I would be seeing can bus failures by now and wondering how I repair a bad crimp buried behind the panel…….

Click to expand...

I think there is enough 'evidence' listed above to validate that can bus issues can indeed be caused by excessive runs of mil spec wire.

As to bad crimps... to some folks delight (because I rarely advocate for soldered connections), I do hand solder each CAN bus connection. These connections are critical, and a hand soldered connection is definitely superior in this application. Please note I said 'hand solder' not solder sleeves! I then cover those connections with dual wall adhesive shrink tube.

Walt said:

How about if you lose your ADAHRS? Now you're relying on your backup instruments (assuming you have one).
(Don't count on the back RS232 lines to save you as they will only work with a complete CAN failure.)

Click to expand...

So I thunk it out... ha ha. I have two and they are 100% independent, by different manufactures and have different back up power sources.

RS232 is for GPS, and the G5 has internal GPS with it's own antenna. The EFIS has it's own TSO'ed WAAS GPS with it's own antenna. I am not relying on only the Garmin GPS175 only. I also have independent and separate GPS/Antenna for ADS-B in. BOTH the G5 and EFIS have magnetometers and loss of GPS will cause some degradation but it will still give heading and Attitude and Pitot/Static.

So to sum it up, 4 GPS w/ seperate 4 antennas, 2 AHARS, Two Air data (airspeed, altitude) . A backup to a backup is my IPAD and Handheld transceivers with basic VOR/LOC Nav. None of this has much to do with Can Bus. The G5 can operate in barebones stand alone PFD mode, I am IFR light to be sure. But we can get into philosophy and how much redundancy do you need or want? Key is redundancy and independence. I have two of everything critical and they don't share or affect anything but ships power (but both have their own discreate backup battery).

Walt said:

You're obviously a more experienced and much better pilot than I, but for me losing the PFD and autopilot would be 'exciting', don't think I'll die but would definitely rather avoid it. Can I hand fly an approach with Ipad and G5, yes, but never had to while actually in IFR conditions.

Not sure which RV you are building but assuming a late model with a standard G3X suite, there is no way you could do a CAN bus with 20'.

Click to expand...

Well to stick to topic Expensive Can Bus I don't think the risk is that critical. We can agree to disagree. I will always have two PFD's (with real AHAR's) unless I have dual failure. The G5 has lighting protection. As long as I have Attitude, Altitude, Airspeed, Mag Heading I can fly the plane in cloud. Loss of Autopilot does not bother me.

Look at 1970's technology, Vacuum gyros, VOR/LOC/GS/MB and the only redundancy was electric Turn Coordinator. You may have heated pitot (not required) and alternate static (not required). It worked for half a century and still does. No electronic flight instruments. It was simple and elegant, but pretty crude by fancy glass standard;

I forgot my ADS-B out has as stated GPS, and AHAR through WiFi to iPad also giving GPS heading, track and navigation (and weather)!
I don't count that. That is a bad day if I am relying on this. Bottom line I have redundancy and isolation of systems. Just the right amount for me.

Again personal mins, not going to pick the worst conditions to fly. Credit card and hotel works. Even in the airlines we no go take-key off due to WX,. or divert from time to time. Commercial aircraft have onboard doppler wx radar (that detects winds shear), three or four of everything. Yes that is mo better. That is a choice for us; I ain't scared. Ha ha.