Fluctuating voltage

[A64Pilot]

I’ve removed and cleaned all the connectors on the alternator, and the battery too of course, everything but the field CB, as it appears to be a nightmare to get to.

‘I assume you get to it by removing the glare shield, but I haven’t looked to see what kind of job that will be either

‘I believe the alt was replaced when the engine was overhauled, which was about 400 hours ago, and I think I’ve determined it to be good.

 

[jaylw314]

Two thoughts--

• When I had this happening due to the master switch, the current wobbles were around 2 Hz.  I don't know if this is typical so take it FWIW
• Consider replacing the push-on connectors or (less technically correct) give them a little squeeze with some pliers to make sure they're gripping the spade connectors tightly

[larrynimmo]

My voltage was going all over the place ....from 12.5 to 15v with no real logic.   I did remake connections at the alternator...no difference....

.but then I was able to find a factory sealed exact model# zeftronics VR on eBay for $200...With guidance of my ai I installed it (plug and play) never below 13.9v and never above 14.1v with a steady 14.0v 90% of the time.

before and after I always had noise like an “alternator whine”....when the avionics shop changed out my audio panel with a Garmin GMA345....ALL noise stopped.

[flyboy0681]

I just responded to another post here on MS for the same issue. I've had this problem twice, the first time was related to the master connectors, the second was the voltage regulator.

[A64Pilot]

Similar but maybe not the same as he says his voltage is stable, which isn’t possible if the amperage is swinging, like that, so if his voltage is stable ,then it’s an indicator issue in my opinion.

Here is mine yesterday, it comes and goes, I’m pretty much most likely down to the pins in the cannon plug or the VR. Just really don’t want to spend $500 on a VR and it not fixit if I can help it.

Especially when every trouble shooting guide I can find says it a power supply problem to the VR

[Ragsf15e]

1 hour ago, A64Pilot said:

Similar but maybe not the same as he says his voltage is stable, which isn’t possible if the amperage is swinging, like that, so if his voltage is stable ,then it’s an indicator issue in my opinion.

Here is mine yesterday, it comes and goes, I’m pretty much most likely down to the pins in the cannon plug or the VR. Just really don’t want to spend $500 on a VR and it not fixit if I can help it.

Especially when every trouble shooting guide I can find says it a power supply problem to the VR

I got some guidance here on MS that I sort of followed but not really.  Wish I had though.  Don’t throw parts at it until you’re sure what’s wrong.  I got a new alternator and new vr and new field and alternator wiring at the advice of two mechanics.  I paid for it all.  None of that fixed it.

Eventually I found the corrosion and fixed it with sandpaper.

Have you checked output at the alternator with the engine running to see if it’s steady there?

[N201MKTurbo]

Mine kind of did that, but it wasn’t quite as rhythmic, it was more random. It turned out to be the regulator.

I would pull the brush holder and inspect it before you spend the money on a regulator. There are versions that have the brush leads riveted to the terminal studs. The rivets vibrate lose and you get intermittent field current. This is assuming you have the original alternator.

The brush holder can easily be removed without removing the alternator.

[201Mooniac]

If it helps any I have a Zeftronics VR from a 1980 M20J (14V) sitting in my hangar that I could loan you for testing.  I can't get it until Sunday when I'm back at my hangar and it is a distance to send it but just thinking...

[OR75]

Had the same issue and replaced the OECO with a zeftronics. Issue gone . 
 

not easy to replace but not that difficult either. Need to remove copilot seat and whatever is on the right avionics stack if any. A wrench with a long extension on the cabin side and another person on the engine side of the firewall. 

 

[201Mooniac]

1 hour ago, OR75 said:

Had the same issue and replaced the OECO with a zeftronics. Issue gone . 
 

not easy to replace but not that difficult either. Need to remove copilot seat and whatever is on the right avionics stack if any. A wrench with a long extension on the cabin side and another person on the engine side of the firewall. 

 

Mine was way easier than that to replace.  I did it with my A&P watching in about 15 mins.  I laid on the wing and got my head into the footwell and was able to R&R without needing anyone on the engine side of the firewall.

[Ragsf15e]

33 minutes ago, 201Mooniac said:

Mine was way easier than that to replace.  I did it with my A&P watching in about 15 mins.  I laid on the wing and got my head into the footwell and was able to R&R without needing anyone on the engine side of the firewall.

Ha!  Mine was even easier!  It was screwed into the firewall in the engine compartment in front of the copilot.  Few screws, cannon plug, all done!  Too bad that didn’t fix it.  

Edited June 1, 2021 by Ragsf15e

[OR75]

2 hours ago, Ragsf15e said:

Ha!  Mine was even easier!  It was screwed into the firewall in the engine compartment in front of the copilot.  Few screws, cannon plug, all done!  Too bad that didn’t fix it.  

For a J, it is inside the cockpit 

[OR75]

2 hours ago, Ragsf15e said:

Ha!  Mine was even easier!  It was screwed into the firewall in the engine compartment in front of the copilot.  Few screws, cannon plug, all done!  Too bad that didn’t fix it.  

It is attached with bolts and nuts , not screws ( at least the original OECO ) 

[A64Pilot]

5 hours ago, 201Mooniac said:

If it helps any I have a Zeftronics VR from a 1980 M20J (14V) sitting in my hangar that I could loan you for testing.  I can't get it until Sunday when I'm back at my hangar and it is a distance to send it but just thinking...

It would help tremendously.

Spruce doesn’t have any in stock, I assume Zeftronics does, but they are almost $100 more than Spruce.

Would you be interested in selling it? If not having a known good to test would be nice, may save me a lot of money, because honestly I’m down to either it being the VR or the cannon plug. I’ve cleaned the cannon plug best I can with no change. Mine is the 1981 original so it doesn’t owe me anything.

There are apparently two different cannon plugs though, one is a large metal Mil Spec and the other is a smaller black plastic cannon plug, mine is the smaller black plastic one.

[jetdriven]

You can replace your unit with a new Zeftronics or PP unit, you just need to terminate  the wires on the terminals of the new voltage regulator. I paid to have a couple of the old style repaired, and it basically cost as much as the new Zeftronics unit  which is probably more modern electronics anyway. It is either four or five wires. I have a diagram that shows what goes to which pin. 

[A64Pilot]

Unfortunately I don’t believe the J model is on the PP’s approved model list, not saying it wouldn’t work though.

I did look as it’s less expensive and while a cannon plug is easier to install, I feel crimped terminals are more secure and easier to replace 

There are four wires, and I believe it’s as simple as power, ground, field and over voltage annunciation

Edited June 2, 2021 by A64Pilot

[Ragsf15e]

2 hours ago, OR75 said:

For a J, it is inside the cockpit 

I know but I couldn’t resist bragging about my old F!  It’s crazy how things moved around between models and even serial numbers.  

[A64Pilot]

Just to circle back and hopefully close the loop, but it seems that the voltage regulator was indeed the problem.

A member sent me his old one for trouble shooting that was replaced when the VR wasn’t the problem, anyway I installed it and it so far seems to have fixed the issue.

‘So while nearly all the trouble shooting trees blame a high resistance connection on the power wire to the VF, apparently sometimes it is the VR.

‘At least I hope it’s fixed anyway.

Oh, and on my J anyway VR replacement is very easy, 5 min job max, two bolts and one cannon plug.

Edited June 15, 2021 by A64Pilot

[Guest]

4 hours ago, A64Pilot said:

Just to circle back and hopefully close the loop, but it seems that the voltage regulator was indeed the problem.

A member sent me his old one for trouble shooting that was replaced when the VR wasn’t the problem, anyway I installed it and it so far seems to have fixed the issue.

‘So while nearly all the trouble shooting trees blame a high resistance connection on the power wire to the VF, apparently sometimes it is the VR.

‘At least I hope it’s fixed anyway.

Oh, and on my J anyway VR replacement is very easy, 5 min job max, two bolts and one cannon plug.

5 minutes! You’re making us look bad.  It takes longer than that to do the paperwork and get a coffee.

Clarence

[A64Pilot]

Yeah, your right by the time I get the computer out and figure out how to print the labels etc, that’s a half hour, or longer, God knows why, but every time is new, I don’t do it frequently enough

just compared to most things under the panel my VR is very accessible. I was worried it would be behind the CB panel that at first glance looks impossible, literally.

On a Thrush the CB panel is hinged with a Camloc at the top, if you need to do anything release the Camloc and the panel lays open just like a big glove compartment door, sit in the pilots seat and comfortably do what’s needed.

‘All Military instruments came out of the front, not mounted from behind and all radios etc are each mounted with usually one camloc at each corner and lift them up.

‘I don’t know who made civilian panels the way they are, must have been a sadist

Edited June 15, 2021 by A64Pilot

[Will.iam]

On 6/1/2021 at 10:56 AM, A64Pilot said:

Similar but maybe not the same as he says his voltage is stable, which isn’t possible if the amperage is swinging, like that, so if his voltage is stable ,then it’s an indicator issue in my opinion.

Here is mine yesterday, it comes and goes, I’m pretty much most likely down to the pins in the cannon plug or the VR. Just really don’t want to spend $500 on a VR and it not fixit if I can help it.

Especially when every trouble shooting guide I can find says it a power supply problem to the VR

Is it just me or does your panel that has the airspeed indicator in it vibrating much more than the panel with amp meter?

[A64Pilot]

whole center panel is on rubber mounts of course. I was at or close to idle and four cylinders are rough, plus I think it’s a trick of the camera that makes it look worse than it is, but it does move some.

‘It’s not you

Edited June 15, 2021 by A64Pilot