negative amps

[aajones5]

I often get a negative reading on my ammeter when flying, its very slight but its definitely negative. Based on what I understand this means the battery is discharging more than it is receiving charge from the alternator? Is this a bad thing? Also when I try to charge my phone or ipad from the cigarette lighter sometimes they'll say they're charging but the battery will still be draining or charging very slowly. My instructor said this might be an alternator problem or a bad voltage regulator. I just put in a brand new battery since my last one wasn't holding a charge, but do y'all think my alternator might be bad as well?

[ArtVandelay]

What is the voltage?

[Guest]

Normally the ammeter should be on the positive side.  After start it should be a bit higher, retreating to near zero as the battery recharges.  Knowing what the buss voltage is would let you know if it's a defective ammeter or an actual fault.

Clarence

[XXX]

I believe the iPad needs at least a 2 amp charge while in use to actually charge, otherwise it is using more juice that it is taking in. The cigarette lighter adapters only supply 1 amp so you will slowly be discharging if you are still using the device.    This is a great option and is approved...

http://www.aircraftspruce.com/pages/ps/ipad_usb/trueblueusb11-12159.php

[1964-M20E]

Ok

What year is your C model?

Do you have the maintenance manual that shows how and where the shunt is wired into the battery and charging circuit?  There are two ways it can be done.  One will show charging or discharging of the battery the other will show alternator output.  I believe Mooney used both methods over the years.

Does it have a generator or alternator?

Do you have the old mechanical style voltage regulator or a newer electronic type? (the newer electronic types generally are better)

If you plane does not have a volt meter installed then use the cigarette accessory plug and fashion an adapter so you can hook a digital volt meter to it and watch your volts during these episodes.

Your voltage should be 13.8 to 14.1 volts when flying.  Generators on the ground at a low idle 1000rpm or less will not charge the battery well or at all.

If you are less than 13.5 volts in flight then you may just need to adjust the voltage regulator.  If you have a mechanical type I'd look into replacing it with an electronic type but I would adjust it initially just to verify the alternator or generator is capable of maintaining 13.8 to 14.1 volts.

Finally if you have a generator and determine it is the problem you might consider converting to an alternator.

 

 

 

 

 

[Guitarmaster]

What John said  ^^^^^^

[aajones5]

I don't have my service manual with me that's in Hattiesburg, but I'll be there on sunday so I can look and check the voltage. I do however have a bunch of electrical schematics for what looks like everything in my plane I'm just not the best at reading it. I'll probably be putting in that adaptor too when I get my EDM put in

[Yetti]

Simple stuff.  Check belt tension

Sounds like you might have a mechanical regulator.  They can be adjusted, but it is a dying art form.

[carusoam]

+1 on John's voltage discussion.

My JPI is my voltage indicator...  very accurate compared to the old analog ship's gauge.

If your system is working, it will be showing good volts.

If it is draining, the volts will be going lower.

get used to the name Zeftronics.  See if it is in your logs anywhere.

Best regards,

-a-

[HRM]

On 4/21/2017 at 6:48 AM, Chupacabra said:

This is a great option and is approved...

Jeez-loueez! 0.3 AMU. Not on the CB approved list, this one is:

[aajones5]

So a quick look at my maintenance manual says I should have a Prestolite alternator, whether or not this has been replaced with a different brand is something that I will have to figure out going through the log books. Wasn't able to test bus voltage yet, but on my flight back I had to use the landing light and notice throughout the whole flight I was sitting between -15 and 0 amps and then when I turned on the landing light it shot down to -30

[aajones5]

I've got a hartzell alternator P/N ALY 8520 that was last overhauled about 600-650 hrs ago in 2010

[Yetti]

Get an LED landing light.  Sometimes people think their planes are tractors and install Wheelen PAR 46 LED lights off Amazon.  You have a charging problem. Alternator or regulator or wiring.   When I took my alternator off to install the starter.   The lug on the end of the wire fell off on in my hands.

 

[aajones5]

Other than testing the volts at the bus bar which I'm going to do hopefully tomorrow what else can I do? Keep in mind I've got no idea what I'm doing when it comes to electrical stuff but my flight instructor can help.

[jamesm]

I am not sure how helpful this is nor  do I know  where you are in the the troubleshooting process but both Hartzell and Plane Power  has a niffy troubleshooting guide. I realize that you don't have Plane power but steps should somewhat applicable. 

 

http://hartzell.aero/article/top-tips-for-troubleshooting-your-aircrafts-alternator/

http://www.plane-power.com/pdf/troubleshooting_Single_Engine_External.pdf

Good luck in  your troubleshooting efforts.

 

James '67C

[Guest]

19 hours ago, aajones5 said:

I've got a hartzell alternator P/N ALY 8520 that was last overhauled about 600-650 hrs ago in 2010

Worn brushes are quite common failure and easily checked.

Clarence

[cnoe]

... what else can I do? Keep in mind I've got no idea what I'm doing...

Perhaps calling an A&P might be the best course of action?


Sent from my iPad using Tapatalk

[aajones5]

Perhaps calling an A&P might be the best course of action?


Sent from my iPad using Tapatalk

Well this will be my route after I've exhausted everything I can do myself.


Sent from my iPhone using Tapatalk

[bradp]

In my case my ammeter shows negative amps at baseline (master off) and when I've been flying. It appropriately deflects further negative engine off with an electrical load. My JPI shows 13.7-13.9 when the engine is running. It's just the gauge being 38 years old and the needle malpositioned.

 

Check your gauge and check your voltage across the bus when charging as mentioned in numerous posts. A voltmeter instrument is a very useful thing. They can be had for less than $100 on eBay used.

 

Sent from my iPhone using Tapatalk

. Master off...

 

 

 

[SantosDumont]

I just had to learn about voltage regulators. My symptoms were no amps until after flying for a while and volts less than 13.  The voltage regulator is what tells the alternator to turn on and how much power to crank out. My voltage regulator was a old mechanical Deltoelectric VR415-F. Replaced it with the Zeftronics electronic voltage regulator and whadda know now I get amps on start and 14.1 volts. 

[carusoam]

A) get volt meter. Plug in the cigarette lighter kind works like magic.

B ) read what the volts are at the cigarette lighter.

C) discuss what you are seeing then.

D) Keep in mind the amp meter is no longer a familiar instrument for many people.

E) An amp meter that no longer works can be even more confusing.

F) if you are not an amp meter, volt meter guy, you surely don't want the old deltaelectric voltage regulator that came with the plane.

G) Step two: research the proper Zeftronics device for your plane.

H) those carbon contacts in the generator are extralong when they are new. If they are nubs now, there is a lot of carbon dust that has been spread around the area along the way...

I) make friends with a mechanic.  Some of these ideas can be discussed over a cup of coffee.

My C got new carbon contacts before it melted all the soldering out of the generator.  Turns out the electro delta sticks and stones and springs, voltage regulator decided to take an extended break....after forty years...  

[SantosDumont]

My favorite part of the Zeftronics regulator is the green light that says, HEY I'M WORKING FINE.

[Dave Colangelo]

Depending on how you have things wired up a discharge reading means that your alternator/generator is not capable of outputting enough current to drive what ever you have in your aircraft, thus you are also drawing some from the battery to make up for the lack of current available. In turn this also means your battery is not charging (generally speaking). Having proper voltage does not always mean that you are also driving enough current through the system. You can have a circuit at 12V dissipating 100 Amps or at 12V dissipating 1 Milliamp and your volt meter will read the same thing in both cases (in this case your power factor will differ P = IV). Your voltage regulator will work to keep the voltage as constant as long as there is enough current to run it but a faulty alternator/generator may not be capable of driving the full load it needs to. In this case it may be worth having the alternator/generator bench tested or rebuilt.  

Low loads can also be the result of a slipping alternator belt which you should check.  

Note: Volt meters are applied in parallel with the circuit or from a point to a good known ground. i.e. voltage is measured "across" something. Ammeters are applied in series to the circuit so something somewhere must be disconnected and have the ammeter put in between it. The exception to this is some that can measure flow via magnetic fields and can be clamped onto wires (these are in my opinion less than accurate). Be careful when putting ammeters into a circuit as you need to use wire that is of a sufficient gauge to handle what you are measuring as well as having a meter capable of handling it. Most Volt meters will handle most of what you can realistically encounter.    

As mentioned it may just be an old dated ammeter that is out of alignment.

 

Regards 

Dave

Edited April 26, 2017 by Dave Colangelo

[carusoam]

Technical thoughts. See if this helps any..?

Our ammeters are volt meters calibrated to read amps... what they are technically measuring is the voltage drop across a known, precise, (low resistance) resistor called the shunt.

If the alternator isn't charging...  the battery voltage won't be 13.8v

If you get a cheap voltmeter and it says 13.8v, the alternator is probably working...

If the cheap voltmeter says a number like 11.8v, the alternator is probably not working...

If you start the flight with a fully charged battery and it reads 12.8 volts and after some time it says 12.7v, then 12.6v   It is a sure sign that the battery is not getting charged properly.

PP thoughts only, not a mechanic...

Best regards,

-a-

[aajones5]

I had a flight the other day that was particularly long, 6 1/2 hours with a brief stop and as I was coming in to land I switched on the landing light which pulls a lot of amps and as a result my gps cut off and restarted so I'm thinking its not the gauge and actually a problem so I'm going to schedule to take it to a shop this week