Hey guys,

I'm starting to get frustrated, I'm in a spot where the radio shop has replaced the voltage sensor, the alternator, and the voltage regulator and yet I'm still having intermittent charging issues.

Without any real pattern, I would have the low voltage light come on during flight and voltage would indicate that the alternator was not charging. Generally, one cycle of the alternator switch would resolve the issue.

Radio shop replaced the voltage sensor and that did nothing. I asked about troubleshooting, they said parts changing was cheaper.

Then, they replaced the alternator and regulator. The fault went away for a few flights.

Then today, it came back with a vengeance, the alternator was dropping out every few minutes and rather than resetting with one cycle of the alternator switch it would take 5-6 on-off-on cycles to get it to come back.

Has anyone else experienced this and have some insight on what I might do next?

Three comments here, based on nothing more than personal experience. 1: Find a different mechanic. 2: troubleshooting a problem is always cheaper than throwing parts at it until it goes away, unless you are making a profit off of the parts. 3: If the problem goes away by flicking the switch, start by replacing the switch.

How’s the belt look ? Is it loose ?

I would check all wiring connections in the alt field and charging circuits. Any loose crimp or connection will result in symptoms as described, because it breaks the field momentarily and the regulator then pulls the alternator offline.

And let’s be honest the charging system is brutally simple. Different mechanic.

I don't know if this will help but.... On my airplane there is an over voltage relay located under the panel on the left side. The way I understand it, if it senses overvoltage it will open and the "low voltage" light will come on. Not intuitive but that's the way it works... once it opens you now have low voltage because it breaks the circuit. Mine was a little different than what you are describing as mine failed in the open position. It took quite a bit of troubleshooting to find the culprit. We spent a lot of time testing the alternator, replaced the regulator, and scratched our heads and cursed before my mechanic finally found it by studying a wiring diagram.

It looks like this:
https://www.aircraftspruce.com/catalog/pnpages/07-00638.php?gad_source=1&gclid=CjwKCAiA-ty8BhA_EiwAkyoa3ybSwDGC4tNtO4cgDzNvmNvC09mG_zrs22v63XcaCHw2-r8Opr2sQhoCQxgQAvD_BwE

Caveat... I'm not a mechanic.... but it sounds like your overvoltage relay could be opening. Cycling the alternator switch is what resets it (mine would not reset). Maybe it's bad. You might actually have an over voltage situation but that doesn't sound likely if you replaced the alternator and regulator.

Thanks everyone, I sure appreciate the help, the way it was dropping out and intermittently resetting sure feels like a loose connection issue. It's definitely behaving differently from before, I supposed it could be a new and separate issue, but it's hard to tell. I took Wednesday off to look it over myself, I can't mess around because I need to fly down to SMO next week. I'll report back with any findings.

If you have a plane power alternator/voltage regulator combo, they publish a trouble shooting guide on their website that is helpful. Test for any grounding faults/loops to include the primary bonding strap from the battery negative terminal to the engine block, and engine block to an appropriate point on the airframe. These connections are often overlooked and it's amazing the amount of havoc a loose or otherwise compromised (corrosion etc.) connection can make. It's easy to spend a fortune on parts and labor only to discover it was a $100 fix all along. I've been there . . . . Good luck.

Wrote the following yesterday but had power issues so couldn’t upload:

You have a Volkswagen bug? 6v or 12v

Kidding, mostly sure you have a later 206 but hay, you know better right: who you are, where you are, what are you doing?

Panel switch is often the culprit based on the info you provided and often can be made to fail running in the ramp by just fingering it around. But not always.

Bummer you don’t have a mechanic that knows how to do basic Alt/reg troubleshooting, it’s fairly easy and quick. They usually work or they don’t

You have the secondary ground from alt case to engine case or better yet to ground lug behind/ under the battery box?

I’ve also had the field and Alt breaker fail one time or another and they are hard to find if intermittent. But once you trouble shoot and verify the Alt/reg are working then you can look at these.

And sometimes it’s just a gremlin ass kicker that takes time, patience, and a masters in Yoga Technologies

Rocket

And if you do have plane power, their helpdesk is downright awesome. Spoke to a real knowledgeable guy who called back twice later to be sure that my problem was fixed. I was amazed in today’s “we are here to help, please hold” world.

This isn't going to help you troubleshoot, but....I was taught with electrics, particular these Cessnas, NEVER reset the alternator more than once or twice at the most....leave it failed, and troubleshoot.

First, it's almost impossible to find a fault if it isn't failed.

Second, as noted above, there is an OVERvoltage relay in there....if your system trips on overvoltage, and you reset it more than once or twice, it could easily fry some very expensive avionics. Worst case scenario, it's also a great way to light things on fire....

Good luck, as others have said, these kinds of gremlins can be frustrating, but most mechanics have been down this road before.....find one who has, and has had success. An instant clue that you need a new mechanic: "He said it's cheaper to R and R rather than troubleshoot."

MTV

Thanks again for all the tips guys, it really helps.

The master switch and field breaker were replaced today, the next step would be replacing parts that have already been replaced. It was suggested that the new alternator, which when replaced a few months ago eliminated the problem temporarily, could now be defective.

Couple of questions:

1. With a mostly steam gauge setup, how long will the battery last without the alternator?

2. Does anyone know at what voltage the overvoltage circuit will cut out? The low voltage level is indicated in the manual, but not the high voltage. It was noted that on the ground, the alternator was putting out over 28 volts, which the radio shop commented as being high.

I'm going to flog the plane in the morning and see if I can get it to fault again and try to monitor voltage closely to see where it's at when it cuts out.

I had a very similar problem on a customers 182. Figured out that if I would just wiggle the switch instead of going full on/off the problem resolved itself. Easy fix, replace the switch. I'd start there and with connections long before changing expensive parts. I agree with the above, find a new mechanic...

When we bought our O-300 powered alternator it had relatively recently had an STC'd alternator installed. The logbooks and invoices for work included a lot of time by the shop working on it throwing parts at the generator and it's regulator, until the alternator was changed, along with switching to the alternator regulator, new wiring to the master switch, new master switch, new breakers to go with the alternator. And it STILL had issues because within 50 hrs they sent the alternator out and had it repaired by the mfg.

When I did a prebuy on it I noticed when the beacon light was flashing with the master on sometimes the master relay would buzz.. but only sometimes. Got it home and it was one of the first projects. After inspecting everything, found that when they had re-wired the master and alternator they had grounded the master switch by putting the ring terminal on a screw behind the instrument panel that had extra threads sticking through the screw, with a plain nut. The plain nut had partway backed off and there was a poor ground for the master switch, which caused the master relay issues and very possibly why that new alternator had to be reworked (or they were still "throwing parts at it")

Perhaps you have a poor terminal crimp, loose connection or other wiring issue causing this?

I had to fix/rework a lot of the stuff the previous owner's shop worked on like this. New parts aren't worth anything if the workmanship is poor...

Well,

Regulator was replaced again today. Went for a test flight and no faults. Time will tell.

My biggest question still remains - at what voltage does the high voltage cutout kick in?

The old (recently installed) regulator was charging at 28.8 volts, the new used one is charging at 28.4. Perhaps 28.8 is too close to the cutout?

CParker wrote:My biggest question still remains - at what voltage does the high voltage cutout kick in?

The old (recently installed) regulator was charging at 28.8 volts, the new used one is charging at 28.4. Perhaps 28.8 is too close to the cutout?

I doubt that 28.8 is too high. The OV relays for the 12 volt systems are called "16 volt" and the OV relays for the 24 volt systems are called "32 volt" on the Spruce website. That's anecdotal evidence but it makes sense. Opening the relay at 28.8 would be pretty sensitive for a system that normally puts out 28.5 volts.

Find your OV relay and look at the label. The specs might be written on it.

https://www.aircraftspruce.com/catalog/eppages/zeftronicsreg2.php

Ok, so here's an update:

The radio shop replaced the regulator again, the fault was reproduced while bench testing it. What seems to have happened was when this problem first arose the regulator was replaced, then the alternator, and the alternator may have been what damaged the original regulator and since damaged the new regulator before it was replaced.

Definitely not happy about the fact that I replaced the switches, breakers, regulator (twice), and alternator all because of one bad alternator. I have to imagine the alternator could have been bench tested to check for waveform before the guns started blazing.

I'm not going to let this happen again, I want bench test proof before any electrical component is changed.

Also the cutout is 31.6 volts

CParker wrote:Ok, so here's an update:
<snip>
I'm not going to let this happen again, I want bench test proof before any electrical component is changed.

Ouch, that was expensive.

Older Cessna's have comparatively simple electrical systems, similar to cars of the same vintage. With suitable knowledge and tools, you may not even have to remove parts to the bench. All my techs started with:
https://dam-assets.fluke.com/s3fs-public/2418158_6003_ENG_A_W.PDF?VersionId=qo.QW_qrN_WRGQxW38brNJiPdPtRhMl3
and
https://www.mouser.com/pdfdocs/1547394_0000_ENG_K_W.PDF
In the latter, refer to Figure 4 "Checking alternator ripple voltage", which is helpful if you don't have an oscilloscope to examine waveforms.

Fluke also offers much help at
https://www.fluke.com/en-us/learn