FX3: intermittent zero amps, spiking oil temp, strobes tripping off

[Andy]

It still sounds to me as though there are two separate issues.

Whatever the malfunction of the strobes, the alternator should be able to keep the battery current positive after engine start.

There is no external strobe controller. The strobes are synchronized by a shared "sync" wire. The flash pattern is more complex than seen by the eye as each visible flash is made up of many shorter flashes. This scope trace shows the visible flash sequence. (Stobes as fitted to FX-3 serial 100.)

[hawgdrvr]

These lights these days are quite computerized and as you mentioned Andy there is more than meets the eye in how they strobe and sequence. I posted my saga from the beginning of the year on Flightinfo.com with my landing light upgrade. Long story short after working with Pete and Mark in figuring out why I was com jamming myself with the lights on, static on the radio, ensuring I had a good ground, etc. etc. in the end it was a defective light. WAT was great to work with and I could not praise them enough for their support and handling of that matter. I bought the lights from aircraft spruce, WAT sent me replacements and the problem was instantly solved. WAT's replacements were manufactured a year later than what aircraft spruce shipped with 2021 lights (in Jan of 2024). It was presumed to be a bad voltage regulator within the light. Moral is, these lights are computers. A bad board, component, etc. can cause issues as described, is my guess. Chase it for days, weeks, months or replace and see if that resolves it. AeroLED's or WAT (one in the same now I think) would probably warranty replace or offer advice to test. Just hope you can find resolution and go enjoy that amazing plane @cavok.

[hawgdrvr]

Hmmm, the sync wire sounds suspect, I wonder if there is a bad connection somewhere with that?

Couldn't you easily pull the 3 light assemblies out and bench test them? All you should need is a 12V source (i.e. starter battery). You could even pull the on/off toggle switch from the panel and mock up the same wiring with power and sync wire I presume and see if you can reproduce the issue in a bench test?

[Andy]

Hmmm, the sync wire sounds suspect, I wonder if there is a bad connection somewhere with that?

The wiring schematic shows 2 plug breaks in each of the 3 strobe/nav light wire runs (for the wings I expect those connectors are at the root and tip). There is also a bundle of wires and blade connectors in the Nav/Strobe light jumper wire assembly between the panel and fire wall.

There is lots of potential for a bad connection. Intermittent faults can be very hard to find but, if I understand the strobes and nav lights, it should be possible to disconnect any two and still have the remaining one work correctly.

I believe this reference is correct for my nav/strobes but I don't know what range of FX-3 serial numbers it would be applicable to. (Pete- do you have a better reference for the strobes fitted to this problem aircraft?)

https://www.aveoengineering.com/down...traDayLite.pdf

I also have a mod 3 version on file but have not checked what the differences are. The mod 4 data sheet is later than my build date.

Tail strobe is here - https://www.aveoengineering.com/down...Lite_14VDC.pdf

[Andy]

The flash pattern is more complex than seen by the eye as each visible flash is made up of 3 shorter flashes. (Stobes as fitted to FX-3 serial 100.)

It had been a while since I looked at those scope traces and that statement was incorrect. The three flashes are visible to the eye but each of those 3 flashes is made up of many shorter pulses that are not individually visible.

I wanted to understand the strobe timing as I thought I may use similar timing in my home brew taxi light flasher. I did not attempt to replicate the micro pulsing.

[cavok84]

Thank you everyone for helping with my issue.

So I spent quite a long time at the airport yesterday. The issue continued with or without strobes (being worse with strobes). It was pretty choppy yesterday, and the issue seemed more pronounced in the chop, but I've also seen it occur when it's as smooth as glass.

I believe this issue all along may have been exacerbated by the strobes, and, perhaps, the temporary amelioration of the issue coinciding with the disconnection of the aft strobe was more correlation rather than a casual effect.

After grabbing the data and making a few return trips, I took the cowling off and checked the alternator closely. All the wires and connections looked pretty good; however, the alternator mount--which has two bolts connecting it to the case, neither of which is safety wired and one of which was missing a washer and had worked its way loose a quarter of an inch.

I added a washer, tightened the bolt, checked belt tension, and had my A&P buddy safety wire the two bolts.

I'm doubtful this was the culprit, as the alternator was very secure even with the loose bolt.


I have some data I'd like to post. Is there a preferred method to upload it to the forum, or would screenshotting relevant snippets be the best way?

AFter I post the data, I'll elaborate a bit more on what I saw with volts/amps throughout the flights.

I believe this issue which has been going on a long time started while still under warranty. Why not ask CubCrafters to warranty replace all three strobes, or at least they should do it in good faith. If not, then determine the vendor for your strobes and ask them for replacements after explaining the issue. I don't know if there is a strobe controller like there is a wig-wag controller, doubt it, but you'd have to review or have Pete tell you the electrical diagram of this system. I hope CubCrafters will help you resolve this in a timely manner.

You're right, I've been having this issue for quite a long time but mistook it for a faulty oil temperature sensor and (probably) a bad aft strobe. My volts 1 which normally runs in the low 14s (13.9/14.3) ran down to 13.3 yesterday during my tests. I reserved this weekend to fly to the Ozarks with a group of guys, so it was pretty disappointing that on the day of my scheduled departure I was forced to make the no-go decision after seeing the battery drain.

[Andy]

I don't think it is possible to paste a screen shot directly into the message. I always use "Manage attachments".

When you are composing the message scroll down to "manage attachments" and click it. That will open a new window which offers "Add files". Use this selection to navigate to a screen shot you have previously made and saved. Upload that file and it will be added to the lower pane. Preview post to confirm it is there.

[Pete D]

I believe this reference is correct for my nav/strobes but I don't know what range of FX-3 serial numbers it would be applicable to. (Pete- do you have a better reference for the strobes fitted to this problem aircraft?)

The AMM Template will have the nav/strobe/landing schematic. It is pretty much the same for all Carbon Cubs, the only thing that has change slightly is the LL flasher over time with different vendors flashers.

Andy is correct, the connection points are at each nav/strobe, at each wing root and behind the panel near the switches. Also the tail nav has a plug near the data plate inside the tail.

2024-10-14 08_32_41-LG Update.jpg

[cavok84]

Thanks for the continued support, y'all. Attached is a snippet of take off data (amps dipping during full power) including some maneuvering.ampsforum.jpgvoltsforum.jpg

[Andy]

I find this data to be hard to read (that was before the post was edited to improve the data presentation) but the data you sent privately shows multiple instances of battery current going negative while engine was running at high rpm.

The characteristics of the EarthX battery make it difficult for me to compare your data with my SBS-J16 data so I hope to receive some data from your aircraft before the problem started.

It may be a good idea to test the alternator before trying to find a possible intermittent wiring problem. If you are willing to pull the alternator for test I'd suggest calling local auto parts stores to find one that can test a Denso 021080-0760. Say Kubota tractor if they don't recognize the part number.

Or you could bite the bullet and buy a new one here - https://www.ase-supply.com/product_p/nd-021080-0760.htm

If you want to try looking for intermittent wiring I'd suggest measuring the voltage at the alternator field terminal while flexing the harness. It should be possible to probe the connector while leaving it connected to the alternator. You need master on for this test but engine does not need to be running.