Voltage problem, need suggestions

I'm having multiple voltage alarms and low voltage issues. This started with an occasional voltage alarm that would go away when acknowledged but more things began to happen recently. First, my set up:

Plane power 60amp self regulated alt
B&C SB-20 secondary alt
PC 680 battery, in use 3 yrs but about 5 yrs old.
8 amp hour battery on dual GRT HX system, new.
VPX pro
Garmin stack, 430W, SL30, 327 x-ponder, intercom

In flight, first low voltage on all three buses, then radio noise before "com service" warning on the 430, continuing to degrad everything on the panel. First coms and then 430 GPS will fail.

Going to VPX page on the GRT HX, see voltages in the very low 12 or high 11 range. Switch to SB 20 and no improvement. Consumption about 7 amps changing as I turn stuff on or off as expected. Individual items will shut down, such as ADSB, flaps, etc

Removed the main alt and had it tested, OK. Changed the PC680 battery, no difference. Checked every wire FWF and all connections, feeds, and diodes, check good.

Starts easy, dual p-mags

Not sure what to check next and hoping this has happened to to someone else who knows what is going on.

My voltage which always runs 14-14.3 started going into the mid 13 volt range after an hour in flight. Nothing really to get excited about, but I was concerned.

Never found anything (I have almost the exact same setup as you, PP and SD20).

A few weeks ago, I gunked the FWF to nail down an oil weep (rocker arm drain tube). Fixed. I have not seen my voltage issue since then.

How these two relate? Beats me. It might have been a bad ground (it will return since I did nothing to fix it). Oil sheen on the shunts, current limiters( I actually put more stock into this theory).

Measure the voltage drop across your master relay. Which side does your alternator tie into? main side or battery side of master relay?

Not much help, just my mileage.

Both alternators tie into main side of battery relay. My feed to the VPX also ties in here. Is it possible the relay isn't holding after initial start?

Since you are using the VPX, I would think to put a voltmeter on either side of the master. If this is a VPX issue and the alternator is getting full field voltage, you should have normal voltage either side. My guess is you do. 11-12 volts is not enough to recharge the battery after cranking.
Bad connection from master relay to the VPX brain box?

Is your plane wired according to one of Bob Nuckolls' diagrams? If so, which one? Turn on all electrical loads and connect the black lead of a voltmeter to battery negative and measure the voltage at various points, like both sides of the master contactor and at the input to the VP-X and etc. Then connect the red lead of the voltmeter to battery plus and measure ground points including engine block and firewall and instrument panel.

Joe,

Its basically his dual alternator, single battery system with some modifications for the VPX and battery that powers the GRT essential gear. This small battery is charged from the same main buss through a diode.

I ran a bunch of voltage checks on the system and came up with this:

Battery voltage at begining of test between terminals: 12.53
Battery voltage at end of test between terminals: 12.30

Battery relay test, voltage as measured to ground terminal of battery:
With master off, battery side 12.51. load side .07
With master on, battery side 12.38. load side 12.35
Master on with 20+amp load applied, battery side 11.52. load side 11.46

Test at VPX terminal, master on but with no load 12.19. with load 11.38

I forgot to compare GRT engine page voltage readouts before I had to go but will compare the readouts with a voltage meter at the VPX terminal soon.

Is ther anything in here that indicates a failure of any type such as the .07 reading?

Paul K said:

I ran a bunch of voltage checks on the system and came up with this:

Battery voltage at begining of test between terminals: 12.53
Battery voltage at end of test between terminals: 12.30

Battery relay test, voltage as measured to ground terminal of battery:
With master off, battery side 12.51. load side .07
With master on, battery side 12.38. load side 12.35
Master on with 20+amp load applied, battery side 11.52. load side 11.46

Test at VPX terminal, master on but with no load 12.19. with load 11.38

I forgot to compare GRT engine page voltage readouts before I had to go but will compare the readouts with a voltage meter at the VPX terminal soon.

Is ther anything in here that indicates a failure of any type such as the .07 reading?

Click to expand...

Can you SAFELY determine (some of) these voltages with the engine running. You should see all you need on the GRT EFIS.

With the engine running, if you don't see 13.8 - 14.4 volts, then your battery us not getting a good charge.

Assuming the case where you say the alternator was checked out, can you easily measure the voltage on that wire (with the engine NOT runnning)? Should be the same (approximately) as your batter/buss voltages. If it is zero, look for a broken wire. If it is the same, check the tension on your alternator belt and maybe recheck the condition of the alternator.


Just some things to look at.

James

Paul K said:

I ran a bunch of voltage checks on the system and came up with this:

Battery voltage at begining of test between terminals: 12.53
Battery voltage at end of test between terminals: 12.30

Battery relay test, voltage as measured to ground terminal of battery:
With master off, battery side 12.51. load side .07
With master on, battery side 12.38. load side 12.35
Master on with 20+amp load applied, battery side 11.52. load side 11.46

Test at VPX terminal, master on but with no load 12.19. with load 11.38

I forgot to compare GRT engine page voltage readouts before I had to go but will compare the readouts with a voltage meter at the VPX terminal soon.

Is ther anything in here that indicates a failure of any type such as the .07 reading?

Click to expand...

That battery is either in a discharged state, or it is sulfated. The open circuit voltage should be 12.8-13.2 volts depending on the condition and age of the battery, 12.51 is pretty low. Even with a 20 amp load a serviceable battery should not drop below 12.5 volts until the battery is at 75% state of charge. 11.52 volts equals less than 10% state of charge.

James,

Good ideas.

I am terrified of standing in front of the wing with the engine running! I saw a guy "get it" and had nightmares for 10 years.

Last time I flew, the GRT was reporting 11.9 to 12.4 max. I checked the wire from the alternater to the relay and it is good. (same voltage at both ends) I also checked the field wire and it is good and with the correct power to activate the field. The belt is tight.

I have two alternators, the secondary is a SB-20 direct drive. It won't charge either. The commonality is that both alternators tie into the main buss at the same point on the load side of the master relay. The mystery is that even with the alternators and VPX power cable connected to that same buss, I am not getting enough voltage to the VPX.

Mike,

The battery is new. It had a factory charge on it and I flew with it for about a half hour so the current voltage is a little low.

I checked all ground circuits, equipment grounds, and power terminals. All of them checked good. I am really suspecting the master relay at this point, mostly because I dont know what else to do.

VPX experts out there. Is it possible the VPX unit is having a bad day! Is there anything in it that could cause this issue?

Just fishing as I am stumped for the time being!

As other have said, a charged battery should have a voltage of about 13. Put a charger on the battery and charge it up. Take the charger off and wait a few hours, then measure the battery voltage to see if is about 13. Just because a battery is new does not necessarily mean that it is good. It probably is, but should be checked to make sure that it holds a charge.
The charger can be left connected to the battery during testing to keep it from running down. Take some more voltage readings. But this time put the red meter lead on battery positive and the use the black meter lead to measure the voltage on the POSITIVE terminals of various components. So you will be measuring the voltage drop on wires from end to end. A voltage drop of 1/2 volt or more is cause for concern. Make the measurements with a heavy load so that problems will show up better. Include the "B" terminals of the alternators in this test.
Another thing to try is to disconnect one of the alternators from the master contactor to see if that fixes the problem. If not, disconnect the other alternator to see what happens. I am thinking that maybe a bad alternator or some other device could be dragging the voltage down. Is any device warmer than it should be? Does the VP-X get warm?
If the master contactor is the problem, then there will be a voltage drop across it. It is unlikely though if the engine starts OK. Let us know what the voltage drops are between the positive battery terminal and the positive side of various loads.

With master on, battery side 12.38.
Test at VPX terminal with load 11.38

Click to expand...

If the above tests were made within a few minutes of each other, then there is definitely a bad connection. What about the crimps of terminals on the ends of wires? Pull very hard to see if a terminal will come off. Or better yet, measure the voltage drop across the crimps.

Just an update, I think the real problem has been identified. It was screaming at me all along, I just didn't see it! It was a "runaway flap" warning. What does that have to do with any of this?

First let me warn you about cheep big box voltage meters. Please check them againat a known standard to see if they are accurate. Mine was about a half volt low acrost the board. In the trash it goes! No big loss, it only cost about $8.00 many years ago. So, all of the voltage readings were low but the differences in voltage readings between two ends of a wire or relay were fairly accurate but the low voltage readings were keeping me sidetracked.

Back to the runaway flap warning, I realized it was another new issue I hadn't seen already and attributed somehow to the low voltage. Funny thing is, the flap motor wasn't runnung and the switches were in the normal or non movement position. Also, the flaps functioned absolutely normal after the VPX was reset. That alone caused me to send off an email to their service department and within about 10 minutes, my phone was ringing with Chad Jenson on the line. Didn't take long for Chad to tell me he was sending the return forms via email for the return of my unit. I guess I'm the second one to fail like this and it sounds like an easy fix.

One other indicator that the cockpit readings were wrong is that the more times I powered everything up, the crazier the readings got. At one of the power ups, one buss read 12.6, another read 9.2, and the third read 2.1 volts. Absolutely not possible.

Chad assured me I would have it back in plenty of time to reinstall it and perform lots of test before OshKosh. Even said he would let me use his personal unit if necessary to get to OshKosh! Kodos to Chad and Aerotronics.

Happy to hear you got to the bottom of your problem, Paul. Now you can shave your head so all the hair can grow back evenly

Anyone who can sort through a vacuum resin infusion for making a plenum (as you have shown) can solve any problem. It has taken me months to get this one stupid VARTM part to come out right.

Good news, bad news! Chad called today and let me know the issue is one of the circuit boards melted! Sodder actually melted and ran off. They don't know why but think high voltage or something like that. No, I have never been hit by lightning and the only nights out of the hangar have been at OshKosh and a few overnight trips. Never fly anywhere near Lightning!

Anyway, that's the good news. Ths bad news is that they don't have the parts to repair it in time for my trip to OshKosh but they do have a loaner that might get to me by Friday. If and this is a big if, I get the loaner before Friday, I hope to still make it to OshKosh early in the week. Not what I was hoping for but might be the best I can do. Hate to scrub it this year but ****, I'm stuck!

Low voltage

I've been having a low voltage problem lately. Sometimes while starting, the engine would barely turn over, other times it would work ok. While running the system voltage would be around 13.1~13.4 volts. I checked the troubleshooting page from Plane Power and went to the hangar ready for a diagnostics session. Getting started I decided to give all the big connections an inspection. The cable below connects the engine to the firewall. When I pulled on it the connection was snug, but it moved a little. Another tug and the wire came out. You can see the wire has been blackened due to the electricity trying to flow through it. Fortunately this wire is plenty long, so I was able to cut it back and crimp a new connector on. Problem solved!
RY is ~2 1/2 years old with 235 hours.






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912ry said:

I've been having a low voltage problem lately. Sometimes while starting, the engine would barely turn over, other times it would work ok. While running the system voltage would be around 13.1~13.4 volts. I checked the troubleshooting page from Plane Power and went to the hangar ready for a diagnostics session. Getting started I decided to give all the big connections an inspection. The cable below connects the engine to the firewall. When I pulled on it the connection was snug, but it moved a little. Another tug and the wire came out. You can see the wire has been blackened due to the electricity trying to flow through it. Fortunately this wire is plenty long, so I was able to cut it back and crimp a new connector on. Problem solved!
RY is ~2 1/2 years old with 235 hours.

Click to expand...

Was this a Vans part or "home built"? Vans had some weak joints a few years back. The pull test on a #2 connector is about 550 pounds. That's right, 550. This should be kept in mind when checking in the plane- the pull force for a good joint is substantial.

I had the same problem with the engine to firewall ground cable from Van's. I cleaned and soldered mine and have had no further problems.

tkracmer said:

I had the same problem with the engine to firewall ground cable from Van's. I cleaned and soldered mine and have had no further problems.

Click to expand...

Good "how-to" courtesy of Aeroelectric Bob here -

http://www.aeroelectric.com/articles/big_term.pdf

Vans supplied part. I don't have a device to measure the pull force, but the new one feels solid, Come to think of it, I can't pull on it that hard either!