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Recurring low voltage issue...

Maverick972

Well Known Member
I have had a recurring low voltage issue and I cannot seem to pin point it.

First, I few months ago I was flying around stopped to visit a friend and could not get the plane to start (Hot, fuel injected and poor pilot techniques all my fault.) flew and the low voltage light came on about half way.

Assuming the battery I charged it. Flew again after about 30-45 min low voltage light comes on.

Flew home and replaced the battery (new Oddesy) as it was 4-5 years old. Test run normal voltage. All is good.

Today finally got to fly as the weather in north Texas has been terrible. Started right up, good run up, 14.2 volts I am thinking good to go. Get on runway, turn on both landing light 13.8 volts, landing lights off 14.2...flew for 30-45 minuets and the low voltage comes on again 12.4... sh!t back to Aerocontry. Low voltage entire pattern. Land, pull back to idle and volts show 14.2. WTF

Now I am frustrated, battery showing 12.8 on the ground. The aircraft has a plane power alternator that has never been a problem. Looked for loose wires and cannot see anything even behind avionics.

I think I have some heat issues behind the dash but that is another post.

Any suggestions would be appreciated. Sean
 
Plane Power 60AMP

It?s starting to make sense, I bounced my landing well enough to wiggle the connector back into place and thus is started to show the correct voltage again.

I will pick up a connection, I did check the belt tension when I replaced the battery as I had the bottom cowl off to fix a cowl flap.

Looks like I am on the right path...
 
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Those are also internally regulated and typically this is the way the regulators fail.

My B&C LR3-B regulator failed in this same way this past week. After I verified it was the regulator and replaced it with an LR3-C I decided to open up the old regulator and see what the problem was.

Watch for a story in KitPlanes on the outcome. :)

Vic
 
I am really in the rabbit hole now regarding alternators. Based on a bunch of reading these threads I am tempted to just say the **** with it and convert to a B&C alt with external voltage regulator if the plug I ordered does not cure the problem.

Is the conversion an arduous task? Maybe Walt can chime in as I am close and he may get tasked to just ?fix the **** thing?... I want to fly.
 
Low voltage

Yep, exact same problem I had with my PP alternator. It was intermittent and, as a result, very difficult to diagnose. After checking everything multiple times, I finally narrowed it down to the alternator and ordered another. Put it on and no more problems since.
 
Take your alternator to a local automotive electrical repair shop. They specialize in alternators, starters etc. The repair cost will be minimal compared to a new "aviation" alternator that is just made with car parts.
 
I am really in the rabbit hole now regarding alternators. Based on a bunch of reading these threads I am tempted to just say the **** with it and convert to a B&C alt with external voltage regulator if the plug I ordered does not cure the problem.

Is the conversion an arduous task? Maybe Walt can chime in as I am close and he may get tasked to just ?fix the **** thing?... I want to fly.

I have done this conversion to many of my customers' airplanes. It has been my experience that the B&C alternators are more reliable. They get the voltage regulator out of the hot alternator environment and move it to the cooler side of the firewall, and the alternators themselves are balanced. It's all I use on my personal airplanes.

I don't wish to start a war on which alternator is better. :) An opinion was requested and I wanted to chime in on experience and practice.

Vic
 
I actually completely agree with Vic. The fact is, I only replaced my PP alternator with another because I am just wrapping up a two year A&P program and I don't hardly have time to fly much less time to change to a different alternator. Next time, and there will be a next time, I will change to B&C for sure. One more thing, the very best alternator shop around looked at my old one (wanted it for a spare) and, after trying multiple sources, they said that the voltage regulator assemble for the PP alternator was not available outside of PP and they will not sell them. Don't want to start a debate, just wanted to relay what I was told.
 
I am really in the rabbit hole now regarding alternators. Based on a bunch of reading these threads I am tempted to just say the **** with it and convert to a B&C alt with external voltage regulator if the plug I ordered does not cure the problem.

Is the conversion an arduous task? Maybe Walt can chime in as I am close and he may get tasked to just ?fix the **** thing?... I want to fly.

Yep, if the plug is not the issue, and taking the alternator to Autozone, or the like, shows it is indeed bad, then a B&C would be my solution as well.

Call B&C before you just order, sometimes they have sales that offset the additional cost of the external regulator. Still, a good value at full list, and with an excellent resource (Walt) nearby, you could not go wrong!
 
PP Alt Mod....

A bit off the subject but... I was given a PP ALT with a bad internal regulator.
Took it apart and it looks like you can take out the reg and hook up an external regulator to the internal field. Have not tried it yet..... John
 
Yep, if the plug is not the issue, and taking the alternator to Autozone, or the like, shows it is indeed bad, then a B&C would be my solution as well.

Call B&C before you just order, sometimes they have sales that offset the additional cost of the external regulator. Still, a good value at full list, and with an excellent resource (Walt) nearby, you could not go wrong!

I've had the same issue with my automotive alternator, I replaced a couple of years ago. My original one lasted about 10 years. Suddenly, I was setting off the voltage alarm. It was intermittent as well. Did all the checks as mentioned in the thread. I too brought it back to have it bench checked twice at AutoZone only to have it checked out correctly. Now, it has apparently gone away. I've flown multiple flights, long & short & all appears to be back to normal.
Next time my cowl is off, I'll take a closer look at the connector to see if there might be a strain relief or other issues lurking.
 
I experienced the low voltage slow drop on my alternator, (O'Reilly) and replaced it twice in 11 years. It was tested and pronounced good both times but replaced under their lifetime warranty. The third episode of lowering voltage was traced to a failing switch breaker I use as an avionics switch. Replaced switch breaker with higher amp and found the screw on the load wire was loose and allowed the connector to make intermittent contact allowing corrosion to form,increasing resistance and lowering the voltage reading on the Dynon SV. Replaced wire connector, polished up the switch breaker terminal and tightened the terminal screw really good and all has been good at 14.2 volts for about a year now. I guess the first two returns really were good. Dan from Reno
 
I just decided to replace the alternator all together so I have a place to start. As I did not build the aircraft I want to time it out myself. Overkill? Probably.The new plane power unit arrived and hopefully I’ll get it in this weekend.
 
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