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Is it normal for amps to jump around?


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HI All

I have a quick question. After installing my EDM 900, I am learning to read all the information being presented and one thing I noticed is my Amps seem to bounce around zero when in cruise flight. Is this normal? I am attaching a screen shot of my last flight with Volts and Amps shown.

Screen Shot 2019-05-07 at 7.21.15 AM.png

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I'm curious also.  My EDM-900 does the same - i.e. the frequent short stretches of slightly negative amps.

Of note these negative amp intervals grew longer right before a corroded contact on my alternator caused my charging system to fail in flight...

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1 hour ago, FlyBoyM20J said:

I had this problem...first noticed it when I started flying my (new to me) 1982 J at night and the panel lights were dimming as the ammeter needle fluctuated.

I posted about it and it turned out to be this:

 

Interesting - I get the dim-bright problem on the panel lights also...

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1 hour ago, DXB said:

Interesting - I get the dim-bright problem on the panel lights also...

All it took to get rid of this was for me to get under the panel and remove all 4 spade connectors from the back of the master switch, use need-nose pliers to tighten up a couple of them, then push them all back on.  Presto, ammeter was steady as a pet rock and all incandescent lights stayed more or less the same intensity.

I think this also made my electric turn coordinator start working more predictably.  It never flagged an error but my timed standard-rate turns were all over the clock until I did this fix, then I started getting more like 3 degrees/second at the indicated bank angle.

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1 hour ago, DXB said:

Interesting - I get the dim-bright problem on the panel lights also...

When the lights start flickering, just reach behind the master switch and jiggle the leads.  If the flickering stops, you have your explanation...

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1 minute ago, jaylw314 said:

When the lights start flickering, just reach behind the master switch and jiggle the leads.  If the flickering stops, you have your explanation...

2 of the leads on mine were loose enough that they might have just come off the spades if I'd done this during flight.  I'm rather glad I tried it on the ground first!

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4 minutes ago, FlyBoyM20J said:

2 of the leads on mine were loose enough that they might have just come off the spades if I'd done this during flight.  I'm rather glad I tried it on the ground first!

Yes, I should have specified doing this on the ground first... :blink:

Edited by jaylw314
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2 hours ago, flyboy0681 said:

We just chased down this problem. After much trial and error it was not the master, nor the alternator but the voltage regulator.

My mechanic and I discussed this possibility...we were kind of thinking that they either worked or didn't but wondered out loud if the VR would indicate problems like this prior to failure.

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Just now, 231LV said:

My mechanic and I discussed this possibility...we were kind of thinking that they either worked or didn't but wondered out loud if the VR would indicate problems like this prior to failure.

Definite possibility.

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Things to consider...

1) Master switch.... supplies power to the master relay.  The relay is supposed to be on or off... if a loose connection or corroded connection on the master switch, the relay can fail to operate properly...

2) Amps being read at the JPI is normally pretty reliable... it is actually reading a voltage drop across the calibrated resistor known as the shunt... then calculating current flow or amps...

3) depending on what VR you have... the voltage can vary a volt or two... from charging to not charging....

4) Older Mooneys use an Amp meter that will show discharge rate or charge rate... negative means it is discharging faster than charging...

5) When listening to the relays... there should be a firm clunk... a light ‘tick’ or rattle is not as comforting...

6) If your relays are original to the plane... 40 or so years for a replacement isn’t too bad.

7) No electronics, is OK for flight in VMC... unless in controlled airspace...

8) No electronics in IMC is not going to work well for very long...

 

Pp thoughts only, not a mechanic...

Best regards,

-a-

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On 5/7/2019 at 9:26 AM, 231LV said:

HI All

I have a quick question. After installing my EDM 900, I am learning to read all the information being presented and one thing I noticed is my Amps seem to bounce around zero when in cruise flight. Is this normal? I am attaching a screen shot of my last flight with Volts and Amps shown.

 

No.   There is a loose wire/bad connector somewhere. 

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