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pjsquare

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Due to continued difficulties, Dynon was kind enough to send me a refurbished D 180. All was fine until I started the engine, at which time the amp meter went wild. It went from a +96 amps then as fast as you could say it, it went to a -56 amps followed by wild fluctuations all over the range accompanied by severe alarms. Checked the alternator, was nominal, DC out put was about 13volts, fuses were all good. After much back and forth with Dynon they were only able to suggest I put a 1000 mf capacitor across the shunt (which cannot be gotten to). I did try a 1000mf cap at pins 24 & 25 which helped only slightly, still the alarms, even with zero input on pins 24 & 25 there was still enough fluctuation to trigger the alarm occasionally. Question, has anyone experienced a like situation and if so is there a fix? Would rather not fly without an amp meter but if I must..... Thanks in advance Paul J.
 
pjsquare said:
Due to continued difficulties, Dynon was kind enough to send me a refurbished D 180. All was fine until I started the engine, at which time the amp meter went wild. It went from a +96 amps then as fast as you could say it, it went to a -56 amps followed by wild fluctuations all over the range accompanied by severe alarms. Checked the alternator, was nominal, DC out put was about 13volts, fuses were all good. After much back and forth with Dynon they were only able to suggest I put a 1000 mf capacitor across the shunt (which cannot be gotten to). I did try a 1000mf cap at pins 24 & 25 which helped only slightly, still the alarms, even with zero input on pins 24 & 25 there was still enough fluctuation to trigger the alarm occasionally. Question, has anyone experienced a like situation and if so is there a fix? Would rather not fly without an amp meter but if I must..... Thanks in advance Paul J.
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More info would be helpful...
Has the system worked normally with a different D-180 that failed and this is a replacement?
Has the engine never before been run before this?
What was teh problem that required you to get a different D-180?

There can be a reading fluctuation that sometimes is resolved with the cap they suggested, but it is very small variation. What you are seeing is not that problem and it would not likely be resolved with a capacitor. Something else is likely wrong.
 
What you describe suggests to me that you have an open circuit into the Dynon sensor input. You can easily check this by disconnecting the connector from the Dynon and measuring the impedance at the connector between the two pins that should connect across the shunt (I don't have the pin numbers handy right now). This impedance should be in the milliohm range. If it reads in the K-ohms, you have found your problem.

Regards,

Rafael
 
The master switch should be off when measuring the resistance. If that is OK, you could try putting a 0.1?F capacitor across Dynon EMS pins 24 & 25.
My D-180 ammeter has never provided any useful information. It fluctuates between plus and minus 10 amps.
As long as the system voltage at cruise RPM is between 13.6 and 14.2 volts, the charging system is working fine.
The ignition system is independent of the aircraft electrical system. Thus the engine will continue to run regardless of the ammeter or voltage readings.
Joe Gores
 
Agree w/ Joe. Same here. The D-180 ammeter is useless. Varies way too much and to my knowledge, no one, including Dynon has come up with a fix that works.
 
MartySantic said:
Agree w/ Joe. Same here. The D-180 ammeter is useless. Varies way too much and to my knowledge, no one, including Dynon has come up with a fix that works.
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Same here. I just ignore it and check the voltmeter. It works about as well as my fuel flow.
 
Follow on to the flucating amp meter

As additional info., I have about 120 hrs on the 12, during the first fifty or so I had an occasional DSAB error show up which cause the auto pilot to kick out, usually a re configuration and all would work well..... for a period then DSAB error again. I lived with this until it got so bad the auto pilot would not stay configured for even a very short time. I sent it back to Dynon, they returned it, the DSAB error problem was still present, and to add to the problem the ASI was reading 10 to 15 kts low ( this was the original D180. ) Sent it back again only this time with both servos and the AP 74. Dynon returned to me a "refurbished" D180, and the original servos and AP74, when I fired things up that is when the amp meter went spazzo, up to that time there was no problem suggested with the amp meter. Dynon now has the "refurbished" D180 trying to resolve the amp meter and other problems which is a subject for another thread. As you can imagine, the cover over the instruments has been off and on a number of times, but eh DSAB error problem seems fixed. Dynon is working with me, but I thought I would raise the issue of the fluctuating amp meter because Dynon suggested this wasn't a new problem and I wanted to see what the experience of others was. You guys have been most helpful, and I will work on some of the suggestions and let you know how things turn out.
Paul Johnson, RV12 177PP
 
pjsquare said:
As additional info., I have about 120 hrs on the 12, during the first fifty or so I had an occasional DSAB error show up which cause the auto pilot to kick out, usually a re configuration and all would work well..... for a period then DSAB error again. I lived with this until it got so bad the auto pilot would not stay configured for even a very short time. I sent it back to Dynon, they returned it, the DSAB error problem was still present, and to add to the problem the ASI was reading 10 to 15 kts low ( this was the original D180. ) Sent it back again only this time with both servos and the AP 74. Dynon returned to me a "refurbished" D180, and the original servos and AP74, when I fired things up that is when the amp meter went spazzo, up to that time there was no problem suggested with the amp meter. Dynon now has the "refurbished" D180 trying to resolve the amp meter and other problems which is a subject for another thread. As you can imagine, the cover over the instruments has been off and on a number of times, but eh DSAB error problem seems fixed. Dynon is working with me, but I thought I would raise the issue of the fluctuating amp meter because Dynon suggested this wasn't a new problem and I wanted to see what the experience of others was. You guys have been most helpful, and I will work on some of the suggestions and let you know how things turn out.
Paul Johnson, RV12 177PP
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Thanks for the additional info. Paul. It helps to better understand the situation.
The shunt system was originally designed per the spec. supplied by Dynon, so we are stuck with what we have. There has been stability issues with the Amp meter, though there has never been anything like you described (swings from max. positive to max. neg.). You never mentioned how it acted before you got the replacement D-180.
The primary consideration is that with your 120 hrs experience flying the airplane, was it acting the same with the replacement D-180, as it did with the original D-180. It sounds like the answer is negative, so they should have had you immediately return the faulty replacement unit, which now it sounds like they have.
I hope you are able to get back in the air soon.
 
Just a guess but

I'd take the alternator off of the engine and have a qualified alternator shop check it out thoroughly. Some times, we get too far from the basics in testing electrical stuff. My guess is that the alternator has something loose inside - wire? connection? solder joint? diode?, etc.
 
E. D. Eliot said:
I'd take the alternator off of the engine and have a qualified alternator shop check it out thoroughly. Some times, we get too far from the basics in testing electrical stuff. My guess is that the alternator has something loose inside - wire? connection? solder joint? diode?, etc.
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I can't disagree that sometimes we get too far from the basics, but in this case we are talking about the integral alternator on a Rotax 912 engine, so for the most part everything you know about trouble shooting traditional alternators doesn't apply
 
Although Scott is correct on his statement on the RV12 Alternator (Dynamo), it is not inconceivable that it could have a defective solder joint or some other problem. I have often thought that if I ever have to remove the Dynamo, it would be easier to just remove the engine from the airframe. It's tight in there!
 
We were able to disconnect the alternator from the regulator and put an oscilloscope on the out put. It had a typical sign wave, not a perfect one. The pattern and voltage out put as seen on the scope, seemed to be consistent with the information we obtained from Rotax. The original D180 showed no sign of an amp meter problem, it only cropped when I installed the "refurbished" unit. The original D180 did fine by all measure except the DSAB error problem.
 
Fight on, paul

It'll be worth it to have everything working 'right'. Don't give in to the 'gremlins'. Please let us know what the outcome is when you find the answer. Thanks.
 
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