Alternator is not charging my battery

[Janat83]

Hello Gyus

I have a problem with my 1968 M20c, when I start engine the ammeter is not charging, it's showing approximately - 5 (discharging), when I add more load like landing lights and fuel pump on it'll go to - 15, and when I add more load like strobes it'll increase and show almost 0 (looks like the alternator is barely compensating that 20 Amps being drained) 

Im not sure how to troubleshoot this issue, I checked all wiring and it looks good, I have Aly-8520r alternator, and Zeftronics alternator controller. 

Appreciating your input

Edited January 20, 2019 by Janat83

[carusoam]

Welcome aboard, Janat.

Where are you at?

Zeftronics have LEDs on them for trouble shooting...

Seek your mechanic to help identify what the Zeftronics is telling you...

The most common problem we see around here is loss of continuity with the field wire... (control line)

Without the field wire, the alternator won’t charge...

PP thoughts only, not a mechanic...

Best regards,

-a-

[Janat83]

I'm at KPOC Brackett field airport in Southern California, got my mooney 3 weeks ago, I'm gonna check the Zeftronics with the mechanic tomorrow and let you know, I already got the troubleshooting manual. Thank you for your support!! 

[MBDiagMan]

It is simple, electrically, to check the alternator to see if it is charging.  Using a DC Voltmeter, check the voltage at the battery posts with engine off.  It should be in the 12 Volt range.  Then check the Voltage with engine running and it should be about 13.5 to 14.5 Volts.  If the voltage while running is the same as it is with engine off, the alternator is not charging or the regulator is at fault.  At that point consult the manual to learn which points to short for a full field check.

Electrically it is simple.  It is simple in practice on a car, but to make engine running voltage checks on an airplane, think it through carefully and BE SAFE.

Hope this helps

[Guest]

10 hours ago, Janat83 said:

Hello Gyus

I have a problem with my 1968 M20c, when I start engine the ammeter is not charging, it's showing approximately - 5 (discharging), when I add more load like landing lights and fuel pump on it'll go to - 15, and when I add more load like strobes it'll increase and show almost 0 (looks like the alternator is barely compensating that 20 Amps being drained) 

Im not sure how to troubleshoot this issue, I checked all wiring and it looks good, I have Aly-8520r alternator, and Zeftronics alternator controller. 

Appreciating your input

Welcome to Mooneyspace and Mooney ownership.

An alternator is a spinning electro magnet.  An easy check is to turn the master switch and alternator field switchs “on”. Then using 2 paper clips joined to form a chain hold them in front of the alternator pulley nut, if the field circuit is working the nut and shaft will be magnetized.  

If there is no magnetism open the right engine cowl, check for broken field power or field ground wires, both are common failures.  If these are OK using a volt meter check for battery voltage on the field terminal, if there is no power you have to investigate further.  Old wires, bad switches open fuse or circuit breaker etc.  

If there is power at the field terminal you could have a bad brush, they are easy to remove from the alternator for inspection.  The brush block is held in with 2 screws or small bolts.

Clarence

[Marauder]

Welcome to Mooneyspace and Mooney ownership.
An alternator is a spinning electro magnet.  An easy check is to turn the master switch and alternator field switchs “on”. Then using 2 paper clips joined to form a chain hold them in front of the alternator pulley nut, if the field circuit is working the nut and shaft will be magnetized.  
If there is no magnetism open the right engine cowl, check for broken field power or field ground wires, both are common failures.  If these are OK using a volt meter check for battery voltage on the field terminal, if there is no power you have to investigate further.  Old wires, bad switches open fuse or circuit breaker etc.  
If there is power at the field terminal you could have a bad brush, they are easy to remove from the alternator for inspection.  The brush block is held in with 2 screws or small bolts.
Clarence

Clarence - do you have any pictures of these wires on the alternator?


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[Janat83]

I've checked the battery voltage and it was showing 11.8 volts no matter if the engine is running or not, i checked with steel blade to see if there's any magnetic field but couldn't notice anything, the wires looks good, I'm gonna check the Zeftronics and see what it says. 

[N201MKTurbo]

I vote bad brushes, but check the field wire for voltage first.

The field wires are two small stud terminals usually at the bottom of the alternator. with the Zeftronics there should be one wire from the regulator and a jumper to ground on the other terminal. Measure the voltage between the two terminals with the engine off and the master and field switches on (if you have a field switch) and you should see battery voltage there. As M20Doc said.

If the brushes are worn to the nubs, there will be voltage at the terminals, but no current flowing through the rotor coil. 

[Guest]

5 hours ago, Marauder said:

 

Clarence - do you have any pictures of these wires on the alternator?


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I don’t have one on my phone at home, but will take one tomorrow.

Clarence

[Janat83]

I checked my Zeftronics, it looks wired that there's no number or tag on the Zeftronics, see attached picture, and there's no light inside any of these holes when master switch is on, however I was able to run the engine and the alternator was doing the same, the more load on the electrical system the more alternator output but it's not cgarging the battery (always showing 0 amps), can anyone advise which Zeftronics is this, my airplane electrical system is 12V

[orionflt]

looks like a VR-415

[carusoam]

See if your airframe logs mention anything about what it is and how long it has been in service...

It is usual to have a decal on it to identify its serial number and specs...

https://www.zeftronics.com/shop/

The one in the picture seems to have a few extra scars and a mix of hardware that may have come from somewhere else?

Best regards,

-a-

[thinwing]

2 hours ago, Janat83 said:

I checked my Zeftronics, it looks wired that there's no number or tag on the Zeftronics, see attached picture, and there's no light inside any of these holes when master switch is on, however I was able to run the engine and the alternator was doing the same, the more load on the electrical system the more alternator output but it's not cgarging the battery (always showing 0 amps), can anyone advise which Zeftronics is this, my airplane electrical system is 12V

I like the screw/bolt combination...kinda like belt and suspenders 

[AlexLev]

Have you checked the obvious? Tightening the alternator belt? That was my culprit earlier. After tightening it, it was charging again, but my battery was discharged significantly so it fried a circuit the alternator circuit breaker in an attempt to charge the battery after the fix which I then had to source/replace (PITA).

Edited January 22, 2019 by AlexLev

[Yetti]

1 hour ago, thinwing said:

I like the screw/bolt combination...kinda like belt and suspenders 

My OCD is triggered.  I vote loose wires.  Only because @N201MKTurbo voted brushes and wires are easier to check than brushes.     When I pulled my alternator, the B + wire came out of the terminal lug.   B+ wire is the big one.

[Marauder]

I like the screw/bolt combination...kinda like belt and suspenders 

Let’s not forget the flat blade screw as well. You need 3 tool to get that puppy off.


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[N201MKTurbo]

2 hours ago, thinwing said:

I like the screw/bolt combination...kinda like belt and suspenders 

Whatever you can find on the hangar floor!

[M016576]

30 minutes ago, Marauder said:

 

Let’s not forget the flat blade screw as well. You need 3 tool to get that puppy off.


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Whomever mounted that thing couldn’t be bothered to get 4 of the same type of hardware, that’s for sure!

[Yetti]

The ty wrap at the end of the loop on a bundle would mean I am cutting it all off and doing it right.   And that engine compartment needs a good cleaning.  You are going to get dirty every time you work on it.

[Marauder]

The ty wrap at the end of the loop on a bundle would mean I am cutting it all off and doing it right.   And that engine compartment needs a good cleaning.  You are going to get dirty every time you work on it.

Let’s not forget about the missing covers for the adjustment holes. Wonder how much crud got into the unit.


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[Janat83]

I have removed the covers for the adjustment holes to see if there's any trouble shooting light thinking that was Zeftronics but looks like this is a VR-415 which usually comes with no tag on this side, I have checked the alternator belt and it was tight, I'm gonna replace the VR-415 and see if that was the issue, the weird thing that the alternator is working but it's not charging the battery, the more load I put on the electrical system the more alternator output will be but overall it doesn't go in positive side of my ammeter and my battery will show low 11.8 volts from time to time and I can't see anything above 12volts on my battery, it used to show 14 volts when engine is running!! 

[Guest]

On 1/20/2019 at 11:00 AM, Marauder said:

 

Clarence - do you have any pictures of these wires on the alternator?


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I took these pictures of a typical Prestolite alternator today.  First picture is assemble alternator.  The second is the brushes removed.  The third is brushes reinstalled in the brush block, retracted and held with a small piece of wire.  Forth is the slip rings where the brushes would make contact.  Fifth is the brush block reinstalled, simply pull the wire slowly, listening for each brush to snap against the slip ring.

Clarence

Edited January 23, 2019 by M20Doc

[carusoam]

Thanks for the lesson, Clarence.  Great pics!

I was not familiar with that retaining wire trick. But, I am now. 

Best regards,

-a-

[Yetti]

Now I am wondering if I should by a set of brushes just because.....   I mean even Harbor Freight gives you a set of brushes with each tool.   Hmmm

[Janat83]

The problem was solved at the end, the Voltage regulator maximum output wasn't exceeding 12V when engine is running (supposed to be around 14V), the alternator is OK, it was just the VR, I tried to adjust it with no hope, I have replaced it with used one and I'll send the old one to be fixed in case I need it in future. 

Thank you everyone for your input and help, I learned a lot from you guys and from this annoying issue.