Low Voltage Troubleshooting?

[Ragsf15e]

Hello,

 I’m not so good at troubleshooting electrical stuff, so some simple steps to start before I hand off to my mechanic would be awesome...

I have a JPI930, and it shows 13.0-13.3 volts pretty consistently.  If I put any draw on the system, it sits at 13.0.  I’m talking transmission, pitot heat, LED strobes, any one of those is noticeable.  Generally sitting at ~3-4 amps as I don’t have much draw.  Battery is new as of 2 months ago.  PP alternator was new from last October annual.  VR is Zeftronics R15300. To be honest, I’m pretty sure it was already doing this before the new alternator and battery...

According to my limited knowledge and the battery instructions, I should see more like 13.8-14, no?

[carusoam]

Sounds like things are drifting lower for some reason...

Any chance you can download the JPI data to Savvy... we can take a collective view at a chart of volts, rpm, and MP to see what isn’t going on...

Sounds like the VR may not be R-ing properly...

If that is happening... check the field wire / control reference wire to the alternator that seems to break often....

Fuzzy PP thoughts only, not a mechanic...

Best regards,

-a-

[Guest]

I don’t believe that this model of regulator is adjustable.  The fact that the buss voltage doesn’t drop below battery voltage say that the wiring is OK.  Have you checked for a loose or slipping drive belt?

Clarence

[Ragsf15e]

35 minutes ago, M20Doc said:

I don’t believe that this model of regulator is adjustable.  The fact that the buss voltage doesn’t drop below battery voltage say that the wiring is OK.  Have you checked for a loose or slipping drive belt?

Clarence

Thanks clarence.  I haven’t, but I’ll take a look at it.  

Yeah, I don’t think it’s adjustable at all.  Last flight was 1.9 hours at 22mp, 2500rpm, 13.1 volts.  I can download the data tomorrow when I get home.

[EricJ]

To answer your question, yes, it should be closer to 14 volts when the alternator is operating.   At 13.0 -13.1 your battery is not ending up with a full charge, which might bite you if you ever have a difficult time starting the motor away from home.

 

[Marauder]

Thanks clarence.  I haven’t, but I’ll take a look at it.  
Yeah, I don’t think it’s adjustable at all.  Last flight was 1.9 hours at 22mp, 2500rpm, 13.1 volts.  I can download the data tomorrow when I get home.

I wouldn’t trust what the JPI is showing either. I have seen the same low voltage with similar amp draw, yet sticking a volt meter on it shows the voltage is 13.8 - 13.9.




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[Yetti]

A light corrosion on the battery terminals could do this.  clean terminals to shiny bright.   Suggest to charge the battery up with a charger.  Use a VOM to check battery voltage at end of charge, then turn on the master and see what the JPI says,  What is the date on the battery?  May have been sitting on the shelf.

[Floyd]

I have a similar issue with a JPI 900.  I consistently shows about .7 volts less then a voltmeter plugged into a lighter socket.

My amps show what I consider a normal load. Yours showing 3 amps is suspect.

[Ragsf15e]

1 hour ago, Yetti said:

A light corrosion on the battery terminals could do this.  clean terminals to shiny bright.   Suggest to charge the battery up with a charger.  Use a VOM to check battery voltage at end of charge, then turn on the master and see what the JPI says,  What is the date on the battery?  May have been sitting on the shelf.

Thanks Yetti.  Terminals should be ok since I just installed it but I’ll check.  Got the battery in February and it was from October 2018, so that seemed ok.

I was wondering about the JPI too... is there an easy way and place to check the actual voltage with the engine running?  Jpi is only indication I have.

[Ragsf15e]

1 minute ago, Floyd said:

I have a similar issue with a JPI 900.  I consistently shows about .7 volts less then a voltmeter plugged into a lighter socket.

My amps show what I consider a normal load. Yours showing 3 amps is suspect.

So is there an a simple voltmeter I can put in the lighter?  That would be a good check.

[carusoam]

There are usb and voltmeter readings for cigarette lighter plugs...

now, where did I see that around here...

-a-

here...   

 

[Floyd]

My voltmeter is in a USB converter.  Sporty's sells on for about $20.  Don't remember where I got mine but I am sure a did not pay more than that for it.

[Marauder]

So is there an a simple voltmeter I can put in the lighter?  That would be a good check.

 

Amazon sells a bunch of different types. If you want one fast, Pep Boys and Autozone sell the cigar lighter type as well.

 

 

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[ArtVandelay]

I have a similar issue with a JPI 900.  I consistently shows about .7 volts less then a voltmeter plugged into a lighter socket.

My amps show what I consider a normal load. Yours showing 3 amps is suspect.

You have an installation issue. My guess is someone installed a diode/LED on the 12v wire that supplies power to the JPI. Pull the glare shield, check the voltage at the JPI circuit breaker which should be normal bus voltage, then the follow the wire to the JPI, it should be only wire.

3A could be normal (mine is 6-7, that’s with taxi lights, strobes, recognition lights...all LED, plus assorted avionics. The fancy modern avionics doesn’t use much power.).

 

 

Tom

[Yetti]

8 hours ago, Ragsf15e said:

Thanks Yetti.  Terminals should be ok since I just installed it but I’ll check.  Got the battery in February and it was from October 2018, so that seemed ok.

I was wondering about the JPI too... is there an easy way and place to check the actual voltage with the engine running?  Jpi is only indication I have.

If you are careful your free volt meter from Harbor freight in the cigarette lighter plug.  red goes to the center.  don't touch the sides.   The standard thing is to use a test lead (alligator clips at both ends) and attach the black test lead from the meter to the frame via some exposed bolt or screw.

The cigerette lighter plug is on the ignition switch circuit in the later Fs

also if you leave the battery charger on and then hit the master.   The voltage should stay the same across the plane and JPI.

[David Lloyd]

It appears your alternator and voltage regulator are working properly.  Suspect is how the JPI 930 was installed.  The shunt to measure the amp draw is normally in line between the alternator and main bus to measure alternator load.  Mounted between the bus and battery will show battery charge or discharge.  Two or three amps a few minutes after start is what the battery would draw, not the total amp load of the system.  If you turn off your alternator (pull field breaker if not a separate switch) do you show a negative amps?  If so, you need to find a competent mechanic or radio shop to review paperwork and what it takes to make it right.

[ArtVandelay]

This one tells me the voltage and when a usb device is plugged in, it will tell me how many amps it’s drawing.



Tom

[Ragsf15e]

Tried Oreilly auto parts on the way to fly home from KBOI.  No luck.  Ill get one on Amazon and check it. 

This is what I saw on the way home (100 ROP, about 147ktas because you know you’d look).

 

[Ragsf15e]

On 4/22/2019 at 4:37 AM, Yetti said:

If you are careful your free volt meter from Harbor freight in the cigarette lighter plug.  red goes to the center.  don't touch the sides.   The standard thing is to use a test lead (alligator clips at both ends) and attach the black test lead from the meter to the frame via some exposed bolt or screw.

The cigerette lighter plug is on the ignition switch circuit in the later Fs

also if you leave the battery charger on and then hit the master.   The voltage should stay the same across the plane and JPI.

So I checked the voltage at the cigarette lighter... now I have more questions than answers.  There is no voltage at the cig lighter until I turn on the Avionics Master.  The JPI is obviously on without the Avionics master.  The JPI and Cig lighter check match within 0.1 volt when I power on the Avionics master.

1.  Is it normal that the cig lighter is through the avionics master?

2.  If it's connected through the avionics master, should I still see 13.7ish - I'm still seeing around 13.2volts.

3.  When I turn on everything (LED lights and pitot heat), my voltage decreased to 13.1 and my amps were relatively constant... seems wrong?

(see linked video) - When I turn off everything (including the avionics master), I was at 13.9 volts and about 5 amps which seems pretty good.  When I turned everything back on, I went back down on the voltage. (sorry, I'm still working on the video)

So I looked through flights from the last 3 years on my JPI 930 data.  See pictures.  In 2016 (slide 1 picture), voltage was constant at 14.  In 2018 (slide 2) it was a lot more variable, and more like 13.5.  Now the third picture is from last month, 13.2 ish average.  The voltage scale is the same on the pictures and it's definitely lower.

Am I chasing a non-existent gremlin?  Is my voltage regulator at fault?  

Battery and Alternator are <6 months old.  Zeftronics voltage regulator.

 

 

[Ragsf15e]

Finally got the video link.

https://photos.app.goo.gl/pj3XWE2tvhQ2NXaWA

[EricJ]

It's not unusual for the power outlet to be wired to avionics, I think mine may be like that.   I don't think there's a requirement for it to be one way or the other.

It sounds like the system can't keep up with the load, which could be alternator or regulator related.

 

[Ragsf15e]

7 minutes ago, EricJ said:

It's not unusual for the power outlet to be wired to avionics, I think mine may be like that.   I don't think there's a requirement for it to be one way or the other.

It sounds like the system can't keep up with the load, which could be alternator or regulator related.

 

Thanks.  I have a new alternator (November 2018) and looked at the jpi download on either side of the work.  Voltage appears low and variable before and after.

Thanks for the info on the cig lighter wiring.

[ArtVandelay]

It sounds like the system can't keep up with the load, which could be alternator or regulator related.
 

He is only showing 3 amps. Sounds like VR issue. I had this problem and fixed it with a new VR.


Tom

[Steve W]

3 hours ago, Ragsf15e said:

3.  When I turn on everything (LED lights and pitot heat), my voltage decreased to 13.1 and my amps were relatively constant... seems wrong?

The amps being low in-flight is what should be happening. But I suspect a JPI problem. 

There are 2 flavors of ammeters, one which measures alternator output(a loadmeter) where 0 is bad and anything higher means the alternator is working until you overload the alternator and one which measures battery input/output. From your picture yours should be wired as the second type(0 in the middle and a green charge for + and red discharge section for - ) If you had a ammeter that started with 0 and went up from there then you'd have a loadmeter. Check your POH for the original ammeter and see what it says.

If you're supposed to have this kind of ammeter then what should happen is that you should see is a large charge right after startup(since startup will have discharged the battery some) and then reducing towards 0 as you fly and if you see a discharge in flight then the alternator is off-line or not keeping up. If it's always '3' then you have a probably JPI problem*, if your POH shows a loadmeter then you have a problem(unless someone moved the shunt to a different spot in the circuit), and if you're sitting on the ground without the engine running and turn on the lights and don't see a discharge then you have a JPI problem.

* JPI being either the display or the wiring to the shunt. The M20J for instance has fuses in-line with the factory shunt and if those are kept then a blown or bad fuse can cause a constant ammeter indication.

Edited May 2, 2019 by Steve W

[Ragsf15e]

2 hours ago, Steve W said:

The amps being low in-flight is what should be happening. But I suspect a JPI problem. 

There are 2 flavors of ammeters, one which measures alternator output(a loadmeter) where 0 is bad and anything higher means the alternator is working until you overload the alternator and one which measures battery input/output. From your picture yours should be wired as the second type(0 in the middle and a green charge for + and red discharge section for - ) If you had a ammeter that started with 0 and went up from there then you'd have a loadmeter. Check your POH for the original ammeter and see what it says.

If you're supposed to have this kind of ammeter then what should happen is that you should see is a large charge right after startup(since startup will have discharged the battery some) and then reducing towards 0 as you fly and if you see a discharge in flight then the alternator is off-line or not keeping up. If it's always '3' then you have a probably JPI problem*, if your POH shows a loadmeter then you have a problem(unless someone moved the shunt to a different spot in the circuit), and if you're sitting on the ground without the engine running and turn on the lights and don't see a discharge then you have a JPI problem.

* JPI being either the display or the wiring to the shunt. The M20J for instance has fuses in-line with the factory shunt and if those are kept then a blown or bad fuse can cause a constant ammeter indication.

Thank you.  I do see negative amps before starting the engine and briefly when applying a big load (gear up or down), but the amp reading wasn’t really my worry.  Iwas more concerned with the low voltage.  I’m starting to think it’s the voltage regulator, but I have no idea how to check it.  I think I’ll make a call to zeftronics...