What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Low Voltage

John C

Well Known Member
My EIS 4000 has come on several times with a low voltage warning. I have it set at 12.3 low and 14.5 high. I have started watching it and it wanders up and down from 12.5 to 13.5 throughout a flight. Sometimes it drops to 12.0 or 12.1 (thus the light) and steadily climbs to 13.5.

Started playing with it. On the ground, just after start and during taxi with everything off except the master and alternator switch on, it sat at about 14.2. With strobes, radio, xpndr, and dynon on, it sits at about 13.6.

In flight it wanders even when removing the electrical load. With load or without, sometimes it goes up or down when rpm goes up or down (the whole matrix).

I turned off the alt switch and the voltage just started dropping, 12, 11, 10 , 9 ,8.... turned it on and the voltage started climbing, 8,9,10,...13.6.

I have the Van's 60 amp internally regulated alternator with about 100 hours. I have a Bob Nuckoll's OV-14.

I've read the posts here which suggest to me that the alternator voltage regulator may be getting eratic. Any suggestions appreciated.

Should I pull the alternator, take it to the alternator shop, wait until it quits, put in an external voltage regulator (how would I do that?)

Thanks, John. I understand there is an AeroElectric list. I'll start looking for that.
 
I've seen some of the same symtoms with a loose B-lead at the alternator terminal. It had some arcing & pulled out when it was tugged on. It would show a good voltage on the ground, but then start dropping under loads in flight.

At least it's something to check for---- just in case. As the problem was found when removing the alternator to get it checked. A new terminal & good crimp fixed the problem.
 
check all wiring connections

check all the connections from the alternator to the 60 amp breaker and the connection at the main buss. I had the exact same problem and it turned out that the 60amp breaker was faulty. Also try to wiggle the wire between the 60amp breaker and the buss connections and see if the voltage varies which might indicate a loose connection.
 
It sounds like you have a loose battery terminal or bad contactor.

The key is that your voltage is dropping below 12V-- this can't happen if you have a good battery with a good terminal and a good contactor.

You should also check the alternator belt tension.

Vern

L.Adamson said:
I've seen some of the same symtoms with a loose B-lead at the alternator terminal. It had some arcing & pulled out when it was tugged on. It would show a good voltage on the ground, but then start dropping under loads in flight.

At least it's something to check for---- just in case. As the problem was found when removing the alternator to get it checked. A new terminal & good crimp fixed the problem.
 
Yep

John, ditto on the good replies above or it could be a flaky VR as you mentioned. You could pull the alternator off and have your local parts story bench test it (free). I would go with the easy and obvious first as suggested. Bottom line the or voltage stability performance terriable and not acceptable or normal. Good luck John.
 
thanks all

Since the airplane is opened up for the condition inspection, I will chase all the leads you have provided. Not sure how to check a contactor (whatever that is) or circuit breaker, but will get my little volt/ohm meter out and learn something.

The belt was tight and I will certainly check the B-lead and plug. Firewall forward all the wires and cables seemed ok, but will look again.

Since it is all open, it would be easy to take the alternator to the local shop and see what they say. Soon as I find the culprit, I'll let you all know.

Regards, John. 97 hours and more fun than I can imagine. Keep pounding the rivets and make good crimps.
 
John C said:
Since the airplane is opened up for the condition inspection, I will chase all the leads you have provided. Not sure how to check a contactor (whatever that is) or circuit breaker, but will get my little volt/ohm meter out and learn something.

The belt was tight and I will certainly check the B-lead and plug. Firewall forward all the wires and cables seemed ok, but will look again.

Since it is all open, it would be easy to take the alternator to the local shop and see what they say. Soon as I find the culprit, I'll let you all know.

.

John, the battery could be failing. Is it an Odyssey?

These batteries require an AGM charger putting out at least 14.2V. The standard lead acid battery charger does not put out sufficient volts and will cause the Odyssey to fail very soon if used regularly. If the alternator is failing and not putting out a steady 14+ volts, it too can cause an Odyssey to fail.

dd
 
how Long Has it Done This?

You've got a lot of good suggestions here John, and I'd follow up on all of them. In addition, I'd be interested in how long you've been seeing this behavior. I ask this because if it has been more then a few hours, with the voltage that low, your battery should be dead by now. What I am getting at is that you might suspect the voltage measurement. I'd throw a separate volt meter on the system and see what you are getting out of the alternator, and at the input to the battery.

If this intermittent low voltage just started, and all was well before, then disregard, you've had something go wrong. But I never let a single piece of instrumentation lead me too far down a path without checking it. to many lessons learned in simulators (run by devious instructors...) over the years....

Paul
 
same problem

John, I had the exact same problem with the same setup: Odyssey battery and Van's 60A internally regulated alternator. No problems since replacing the alternator. A relevant quote from one of the King Schools videos: "See things as they are... not as you want them to be." Use extreme caution if continuing to fly with a known problem.
 
UPDATE

I removed the alternator, tested it at AutoZone and it was rock solid at 14.2 volts. I added a volt meter at the fuse to the Dynon at the radio power fuse block. It is powered with the radio switch on. The EIS is powered with the master switch on. Since that time, the voltage at fuse, on the Dynon display, and EIS display are all within a .1 or .2 volt at about 14.2 to 14.4 volts.

The power sequence should be to the master (and EIS), to the radio power fuse block, then to the Dynon. So, if I have 14.2 to the Dynon, I should have 14.2 throughout the system.

Tonight, I turned on the strobes, radios, landing lights and nav lights. The voltage at all three meters was about 13.9 to 14.0.

I tugged at the wiring forward and aft of the firewall and did not find any problems.

Perhaps removing and reinstalling the plug on the alternator did the trick.

As Paul said, make sure the volt meter is accurate. I still have a question about the EIS voltage as the unit heats up but on these cool days, all is good.
 
Circuit Breaker

At 16 years and almost 2600 hours - the low volt gremlins hit my -9A. I've had this before and it's either been my Samurai alternator or a loose wire in the alternator plug.

This time it showed up on departure from Oshkosh this year - on the way in I had been rock steady at 14.2v on the Dynon, but ever since, I've been at 13.6 with excursions to 13.3 and 14.1. I confirmed the voltage with a VM in the cockpit and it matched the Dynon, so we dug a bit deeper. I remade the fastons that connect to the the alt plug with no change. I also had the alt checked and it was 14.4 on the bench.

The only things between the alt and the bus were 4 connections and the 50 amp breaker. Easy checks first, so we isolated the breaker. Input side 14.4v, Output side variable 13.4 to 13.8. Seems we found the winner. Spruce has one in stock in for only 17.50 delivered.

I'll be diving under the dash to fix it midweek. Hope this might help someone out with trouble shooting.
 
Back
Top