Amps going negative intermittently

[hawgdrvr]

I asked TSQuared to bring his SD card home after flying tonight and send me his contents so I can compare numbers of another FX-3, his being a 2019 but also IFR panel.

I wonder what the expected volts should be such as from the alternator? With my recent history of battery concerns which I replaced my SBS-J16, I wonder if all of this is adding up to something such an alternator issue?

[Narwhal747]

If your engine is "missing a beat" in flight occasionally, consider reaching out to Kris at Tac Aero. Bumble bee was doing that when I flew it last fall, but I never did follow up to see if they figured it out. It was a very intermittent problem that would happen randomly about once every 5 hours.

[Andy]

If your engine is "missing a beat" in flight occasionally, consider reaching out to Kris at Tac Aero. Bumble bee was doing that when I flew it last fall, but I never did follow up to see if they figured it out. It was a very intermittent problem that would happen randomly about once every 5 hours.

This happened to me during phase 1 flight test and has happened a few times since. I suspect fuel vaporization in the upper injector lines. It only happens to me at low power and low flow rates.

[Andy]

I wonder what the expected volts should be such as from the alternator? With my recent history of battery concerns which I replaced my SBS-J16, I wonder if all of this is adding up to something such an alternator issue?

Many post ago I said "Not normal. It probably indicates that either the alternator, or the circuit between the alternator and Main Bus, is intermittent."

My Volts1 rises to 14.3 within a few minutes of engine start and stays at 14.3 for the whole flight.

Log it as a warranty issue with support. They may want the alternator to be tested or they tell the service center to replace it. With the cowling off for condition inspection it's not a big job to change the alternator. If you still see the intermittent after changing the alternator you are faced with the likely harder task of finding a wiring problem.

[Narwhal747]

This happened to me during phase 1 flight test and has happened a few times since. I suspect fuel vaporization in the upper injector lines. It only happens to me at low power and low flow rates.

Interesting. If I remember correctly every time we experienced it was in the pattern on downwind at a time when the electric fuel pump was off and power had been reduced to 18" and 2300 rpm or so for pattern work. Maybe turning the pump back on would've helped in our case but the problem only lasted for a split second.

[hawgdrvr]

Both times it's happened to me it has been low power and leaned out so under 7 gph. Sure catches your attention. And yes, fuel pump off. Just seems like an electrical miss in the ignition. May be a question for lightspeed??

As to the amp issue, I emailed Pete at CC and will see what they want to do as I'm heading for condition inspection at a CC service center next Wednesday.

[hawgdrvr]

I emailed CC support and got a timely response which is nice as I'm heading to a CC service center next Wednesday which is an opportune time to have this looked at or fixed by someone that knows the plane vs. my local options. CC responded to check wiring at the alternator, battery, and shunt. Alternators are pretty robust and either work or not.

Next time I'm at the plane I'll check the battery connections under the seat but I don't think there is an issue there as I just changed the battery. This evening I crawled in and looked extensively from below the panel, everything looked very good. I pulled the GDU and inspected the shunt and all wiring and again, all looks very well done and secure. So nothing from a visual inspection at this time. At my condition inspection I'll ask to have things checked after I explain to them the situation.

I'll continue to monitor closely and hope this was a one off occurrence. Odd it happened at least twice this day, once on the ground, once in flight (smooth day, no turbulence).

[hawgdrvr]

TSquared sent me his G3X SD card data. His volts are like yours Andy around 14.1 and in some cases 14.2. So why is mine only 13.7?

Attachment 12359

[Andy]

TSquared sent me his G3X SD card data. His volts are like yours Andy around 14.1 and in some cases 14.2. So why is mine only 13.7?

The alternator max voltage will depend on how the alternator voltage regulator was configured. 13.7 V seems a bit low but it may be within the tolerance for alternator regulator calibration.

Your intermittent charge problem is a separate issue from the alternator steady state voltage.

[hawgdrvr]

From my RV (motorhome) experience with batteries, solar, etc. typically you need the higher voltage for bulk charging of a battery. Lower voltages are for absorb or float stages, so this lower voltage is a little concerning in maintaining the battery which could be related to my recent battery concerns and replacement.

Edit: Obviously there is no charge controller so nothing to regulate voltage for different charge rates, as expected. I did a google search on the Denso and from what I can tell the alternator is rated to produce 13.5V at 25C. Just odd others are seeing what seems to be a 14.1V level and I'm seeing 13.7.