Thorp Air Command - T18.net

I have a Dynon D120 in my plane. As of late, the Amps have been going way up (sometimes showing 62 amps.....when I have a 60 amp alternator) when I am at idle. If I get the RPMs up, the Amps will go down to a where they should be. But, even during flight, the amps oscillate. My amp reading is also reading higher than what I previously recall.

And my voltage, while good, seems to be also oscillating a small amount, where before, I believe it was more constant during steady state flight.

I have checked logical grounds and connectors, I checked the battery and connectors, but to no avail. I installed a larger ground strap from my engine to airframe but no change.

Anyone have any ideas as to what is going on?

I would put an analog plain jane amp meter inline with the alternator out, just to make sure its not the Dynon. Sounds like a run away alternator. Take it off and have it checked by a bonified shop and not at the parts box stores.

If your voltage drop coincides with your amperage increase, it could be a real problem. If not, it's probably the sensor. Borrow another Dynon sensor if you can.

Pick a cold morning, Do a quick start and run-up (as short as possible), shut down and feel around for warm wires, especially the one coming from the alternator. If you are truly drawing 60 Amps, something has to heat up.

Bill's advice to test the alternator is the next easisest thing to do.

If not sensor or alternator, then it must be the regulator.

You may have a problem with the Dynon, but pretty unlikely that anything is wrong with the shunt... they're stone simple - just an accurately calibrated resistor. There is no "sensor" per se. Do you have a separate regulator, or is it built into the alternator? Double check your "heavy wire" connections, including the battery & master solenoid. Check for voltage drop across the solenoid.

_________________
John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE

I also forgot to say that I have also put on a new voltage regulator in a attempt to figure this out. The new voltage regulator didn't change anything. Solenoid connections have been checked too and they are all good and tight.

My voltage seems to be good, and does not fluctuate when things are turned on and off. The voltage fluctuations seem to be random fluctuations. When I turn on the strobes, I see the amps increase (I have my amp meter wired to show the output of the alt) and then the amps decrease when I turn the strobes off. Voltage stays pretty steady during the strobe test. I will the check the alt, amp meter, and voltage drop across the solenoid and follow the other suggestions as well.

I just had to replace my battery. Weak cell was causing load on alternator which caused fluctuations as the various loads came on. The fooler was that the plane started very well even with the weak cell. Load test at the battery shop told the tale.

_________________
Bob Highley
N711SH
SN 835
KLAL

now that is interesting. I would never have thought of that. i'll keep that in mind as a potential culprit as well.

I had a run away alternator Bill, it showed fulxuations in voltage for awhile and it was typically a little low that was a little strange. I gotta whine in my headset whilst flying one morning, it was intermittent, thought someone was keying up or hollering at me or somthing but didn't see any other craft around. A scan of the gauges and the volt meter would peg out during the whine, killed the alternator and headed for home. The long short of it I had it tested and it was gone....It was 5years old.....Dan

I'm still on the hunt. Its been slow. I took a trip past Mt. Rushmore since I found my electrical problem with my Thorp. I also included a photo of the mighty Mississippi River with some fall foliage just off the departure end of the airport in Prarie Du Chien, Wisconsin. I'm back onto my Thorp troubles now. I took my alternator and voltage regulators to a magneto/alternator shop. They said the alternator was good, but the old regulator AND the new regulator I put on were both bad. They said the first one would allow constant over voltage, and the replacement wouldn't do anything, i.e. it was open. I was seeing the same symptoms with both regulators, so I am having trouble digesting that information, but I went ahead and bought a third regulator and installed it. In fairness to the shop, I may have shorted out the second voltage regulator while I was troubleshooting. If I still have the same issues, I'm swapping the battery out and giving that a try. Then if that doesn't work, I'm sending the alternator back to B&C for a test. I'll do a quick ground run tomorrow.

ground run today with the third voltage regulator showed the same symptoms as before. Gonna replace the battery and try it again. I also went and bought a 65 amp externally regulated alternator from autozone. Gonna stick that sucker on there for a ground run. If that fixes my problem, I may leave it on there until I get my B&C shipped back to me. That way I can fly in the meantime. I may just leave it on there. My autozone alternator cost me $30 + a $10 core charge vs. a $700 B&C alternator.

I also switched out my split master/alt rocker switch for two independent toggle switches.....and no change in behavior.

well, I have installed a new voltage regulator, a new alternator, a new battery and new alt/master switches.....and I still get the same thing. Maybe time to look at my wiring....again.

Could the master solenoid cause high voltage and high amps? How?

Jump across master and see what happens?? Check and see if you have a loose connection could cause a high resistance in the circuit. A wire crimp or loose terminal connection could cause corrosion resulting in high resistance. What type of shunt do you have?. Is it external or internal the the meter?

Intermittent problems always make me look for a ground issue. They are most likely to occur in the engine compartment. Wiggle all wires and connections. Something is loose or corroded.
Cubes

Have you talked to Dynon to see if this problem has occurred before ?

I have a Dynon shunt hung on the firewall. I plan to go through the wiring looking for suspect crimps and any knicks in the wiring, and poor grounds. I will have to get on the Dynon board. I haven't discussed it with them. I tend to think the high amp and voltage readings are correct because I have a Microair Transponder that will show the voltage, and it too is showing high volts.