Voltage Regulator or Alternator issue?

Hunter

Hunter

Pre-Flight
Joined
Oct 11, 2016
Messages
54
Location
Alabama
Display Name
Display name:
Hunter
I've been sponging up knowledge from these forums for a while, but this is my first post. Just wanted to say thanks for all of the knowledge I've gained thus far.
I have a new alternator and new voltage regulator installed. I'm cruising along with 14.1volts on the engine monitor (I have on: nav lights, strobe, radios, rotating beacon), then all of a sudden it drops to 12.3volts. I can flip on the landing light, and 3 out of 5 times it jumps back up to 14.1 volts. The times it doesn't jump back up, I can wait a few minutes, flip it, and it jumps up then. This has happened on a couple of flights now. This isn't normal is it?
 
what aircraft? which system? alternator / generator electronic regulator ? or the old vibrator type?

Watch,, there will be a bunch of WAGS / SWAGS / and TLARS given.
 
1965 Cessna 182J, ES-4000 Hartzell Alternator belt driven. I can't find paperwork on regulator, but will run out to hangar and get it today. Petty sure I went back with the same type that came on it.
I haven't learned the slang yet
 
I'd read through all the technical data with the new alternator and voltage regulator. An old analog regulator would typically try to hold the system around 14.25 VDC to keep a constant charge on the battery. If you overloaded the capacity of the alternator, it would drop back down to battery voltage. Maybe you have something different if it's all new.
 
The charging system on an airplane is a deceptively simple system that can fail in an amazing number of ways. On my RV I literally chased charging problems off and on for YEARS without resolution, ultimately replacing the entire system this year -- regulator, alternator, and all wiring -- before pronouncing it fixed.

In my Pipers it was often a loose connection on the back of the alternator causing sporadic problems as you describe. Start there and work your way back.
 
Check the ground, the VRs are usually grounded thru the case, so make sure its got good contact to a ground source, usually the frame, use voltmeter to verify.
 
check the connection for the "B" field on the alternator.....then trace that wire back to the voltage regulator. The B field voltage "regulates" when the alternator is energized and producing current.
 
Checkout_my_Six said:
check the connection for the "B" field on the alternator.....then trace that wire back to the voltage regulator. The B field voltage "regulates" when the alternator is energized and producing current.
Click to expand...
It's fairly easy to rig up a voltmeter on this line to watch what the voltage regulator is doing. I had a voltage regulator that randomly dropped the field voltage to zero...it was sorta a pain to figure out until the voltmeter was rigged on the line.
 
Clark1961 said:
It's fairly easy to rig up a voltmeter on this line to watch what the voltage regulator is doing. I had a voltage regulator that randomly dropped the field voltage to zero...it was sorta a pain to figure out until the voltmeter was rigged on the line.
Click to expand...
great idea.....!! ;)
 
The first thing I would do would be to disconnect the field wire from the alternator. Then run a jumper wire from the field terminal on the alternator to the closest source of battery voltage. Run the engine up to around 1700 RPM and check out the engine monitor. If you get a high voltage reading, like 14.8V or greater, than the alternator is ok, and the problem is either the regulator or the wiring to/from the regulator. If you get a low voltage reading, like around 12V, then the alternator is the issue. BTW, make sure you only run the engine for about a minute if the voltage reading is high, otherwise you might fry something. :(
 
DB1 said:
The first thing I would do would be to disconnect the field wire from the alternator. Then run a jumper wire from the field terminal on the alternator to the closest source of battery voltage. Run the engine up to around 1700 RPM and check out the engine monitor. If you get a high voltage reading, like 14.8V or greater, than the alternator is ok, and the problem is either the regulator or the wiring to/from the regulator. If you get a low voltage reading, like around 12V, then the alternator is the issue. BTW, make sure you only run the engine for about a minute if the voltage reading is high, otherwise you might fry something. :(
Click to expand...

Very easy to fry something doing that. Usually a second person will connect the jumper while the engine is idling, just long enough to see if the ammeter jumps. An alternator, with the engine at a higher RPM, with the field at full battery voltage, can produce well over 100 volts. That will fry the battery, any electronics that are on, burn out bulbs, and so on.

In the 1970s you could buy a little box that you installed in your alternator-equipped vehicle. It switched the alternator's output away from the electrical system and to a 110V receptacle. The field was switched from the regulator to the battery. At 2000 RPM or so it produced 110VDC that could be used to run lights or series-wound motors such as those in skilsaws and drills and the like. I had one on my pickup. The alternator, capable of 60 amps, could produce 6600 watts in that mode. Lots of power.
 
Dan Thomas said:
In the 1970s you could buy a little box that you installed in your alternator-equipped vehicle. It switched the alternator's output away from the electrical system and to a 110V receptacle. The field was switched from the regulator to the battery. At 2000 RPM or so it produced 110VDC that could be used to run lights or series-wound motors such as those in skilsaws and drills and the like. I had one on my pickup. The alternator, capable of 60 amps, could produce 6600 watts in that mode. Lots of power.
Click to expand...

Thread hijack: My daughter's 2004 Toyota had a 110 volt AC outlet in the dashboard. She used that thing for everything, until she totaled the car.

I wish that outlet was standard equipment in all cars.
 
Dan Thomas said:
Very easy to fry something doing that. Usually a second person will connect the jumper while the engine is idling, just long enough to see if the ammeter jumps. An alternator, with the engine at a higher RPM, with the field at full battery voltage, can produce well over 100 volts. That will fry the battery, any electronics that are on, burn out bulbs, and so on.
Click to expand...

Good point, I always leave the avionics switch off when doing this. I've done it quite a few times on 206's and 207's with out a problem, but you are right, there is a chance of letting the smoke out of the electrical equipment.
 
A friend with a Volmer Amphibian (had a pylon mounted pusher engine) used that principle to put electric heat in the Volmer's cabin! I doubt it worked very well though........
 
Little things like cracked wire insulation can have you chasing intermittent alternator shut-downs. It did on mine for a several years until I re-wired the entire airplane. Intermittent electrical issues are hugely frustrating.
 
Jay Honeck said:
Thread hijack: My daughter's 2004 Toyota had a 110 volt AC outlet in the dashboard. She used that thing for everything, until she totaled the car.

I wish that outlet was standard equipment in all cars.
Click to expand...

You can add an inverter to any vehicle for $30. That help at all? Ain't China wonderful?
 
teejayevans said:
Check the ground, the VRs are usually grounded thru the case, so make sure its got good contact to a ground source, usually the frame, use voltmeter to verify.
Click to expand...

Pray tell how you can use a voltmeter to see if the case has a good contact to ground?

Jim
 
weirdjim said:
Pray tell how you can use a voltmeter to see if the case has a good contact to ground?

Jim
Click to expand...
Get a AA battery. Measure and record voltage across the battery. Attach one side of the battery to the voltage regulator case. Attach other side of the battery to ground on the aircraft. Let set several hours. Disconnect battery from voltage regulator case and airframe. Measure and record voltage across the battery. Compare the two measured voltages? Are they the same? Are both not equal to zero? (If both are zero then start over with a fresh battery ya nitwit.)
 
Clark1961 said:
Get a AA battery. Measure and record voltage across the battery. Attach one side of the battery to the voltage regulator case. Attach other side of the battery to ground on the aircraft. Let set several hours. Disconnect battery from voltage regulator case and airframe. Measure and record voltage across the battery. Compare the two measured voltages? Are they the same? Are both not equal to zero? (If both are zero then start over with a fresh battery ya nitwit.)
Click to expand...

I believe I've heard of easier methods. :eek:
 
weirdjim said:
Pray tell how you can use a voltmeter to see if the case has a good contact to ground?

Jim
Click to expand...

Select ohmmeter function attach 1 lead the case, other to a known good ground, should be less than 1 ohm. Don't need to even turn on the master switch. A floating ground can cause all sorts of problems.
 
teejayevans said:
Select ohmmeter function attach 1 lead the case, other to a known good ground, should be less than 1 ohm. Don't need to even turn on the master switch. A floating ground can cause all sorts of problems.
Click to expand...
A voltmeter doesn't have an ohmmeter function. A multimeter does.
 
check your belt tension also
 
I wouldn't be too caviler with electrical system experiments. I went looking for data on destructive aircraft electrical system noise spikes to see what if anything has been credibly documented. I didn't find a lot, but in an old 1983 IEEE paper, the author did determine the most severe electrical noise spike in an older automotive 12VDC charging system is called the Alternator Load Dump Transient. This is when the battery terminal is abruptly disconnected while the system is charging. It's also described in a lot of marketing technical data too.
 
Stewartb said:
Little things like cracked wire insulation can have you chasing intermittent alternator shut-downs. It did on mine for a several years until I re-wired the entire airplane. Intermittent electrical issues are hugely frustrating.
Click to expand...
God, yes.

Here's my multi-year electrical tale of woe:

From Day One, something was hinky with the charging system in our RV-8. In 2013 my delivery pilot had the alternator drop off line several times, so we replaced it with an exact (automotive, 30 amp Honda) new one.

Problem solved...nope.

It never got over 13.3 volts. Ever. This was...enough...so I lived with it until Oshkosh 2014, when the system completely failed on the way home. We flew all the way to South Texas in stealth mode, in radio silence.

Once home I traced all the wiring and discovered that there were 2 wires going to the alternator rather than one. WTH? After some research I found out that the second wire was supposed to go to an idiot light in the dashboard of a Honda, and for some reason it had been connected to ground. We were feeding an intermittent 5 volts to ground.

I snipped the offending wire, capped the ends, and all was fine! I replaced the dead automotive voltage regulator with a high dollar aviation one, and off we went.

Except it still would not put out move than 13.3 volts. But that was "good enough" to keep the battery charged, and we had no issues.

Until this year, two weeks before Oshkosh, the system failed again. Suddenly, 12.6 volts was all we got. I took the alternator into a rebuild shop in Corpus, and swapped it out for an identical model. Reinstalled -- nope, the system was still dead.

Surely it couldn't be the high dollar Zeftronics voltage regulator, could it? I swapped it out for a cheap, $19 automotive regulator. Nope, everything was still dead.

So, it had to be the wiring, right? That's all that's left, right? I dismantled and cleaned every electrical connection in the engine bay. Checked everything with a multimeter. Everything was perfect.

So I had a new alternator, new regulator, and perfect wiring -- but still no electrons going to the battery. It HAD to be the drive belt slipping! That was the only part of the system not new!

Pulled the prop and replaced the belt. Fired it up and....nope. Still 12.6 volts...

What. The. Fluck?

So, we said (by now the entire airport was involved, mostly for the comedic aspects, I'm sure) "It must be an intermittent wiring issue. A transient bad ground. A broken wire inside the insullation. SOMETHING."

So I replaced all the wiring with new.

Nope. Still 12.6 volts! I was incredulous, but the gauges didn't lie.

Then, as a last resort, we thought "maybe the pulley on the automotive alternator is too big, and it's spinning too slowly!" That would explain the low voltage output, even when it was "working"...

So we tried to replace the pulley. Well, it turns out that the old, 1980s vintage 30 amp Honda alternators had a smaller than normal shaft, which meant none of the pulleys at the auto parts stores worked...

Now we were coming down to the wire on Oshkosh 2016. Attendance at OSH is non-negotiable in my family, after 31 in a row, so I was willing to do whatever it took to get it done. After much consultation and research, I did what I should have done back in 2013: I ****-canned the whole system and installed a complete B&C aircraft charging system. New alternator, drive pulley, belt, wiring, and matching voltage regulator.

It wasn't cheap, and pulling the prop off again to install a different sized drive belt sucked, but the end result has been a perfect, rock solid 14.2 volt charging system.

Electrical problems are the worst. (Strangely, I just went through the exact scenario on my '52 Pontiac...)
 
Last edited:
Funny, when I re-wired my Cessna I got a field approval and installed a B&C alternator and LR-14 regulator. Yep, perfect. Yesterday I installed a B&C 40a shaft driven alternator on the accessory case of my new IO-400. Very nice.
 

Attachments

  • IMG_2980.JPG
    IMG_2980.JPG
    185 KB · Views: 17
"Have you checked the air in the tires lately?"
"Maybe you're low on water, maaaaan."

(Anyone who listened to a certain pair of comedians doing their stoner adventures should get the reference...)
 
its never the voltage regulator. It's always something more expensive
 
comanchepilot said:
its never the voltage regulator. It's always something more expensive
Click to expand...

Our problems four years ago was the VR. But it was fairly obvious since it kept tripping for "high voltage" when measurements showed it wasn't ever going high. Cheap and easy fix.
 
comanchepilot said:
its never the voltage regulator. It's always something more expensive
Click to expand...
It might be a bad or intermittent ground. Bad grounds are responsible for a lot of needlessly expensive repairs. Voltage regulators and overvoltage sensors are particularly fussy that way.
 
Thanks for all of the ideas/advice. I checked all of the wires that I could, and only had .03 ohms on the worst one, so I don't think that's it. Zeftronics has been less than helpful in the customer service department, I've talked to them once out of @5 phone calls/messages.
The issue continued on a trip this weekend, one of the times, I let it go down to around 11.8V, couldn't take it anymore, got nervous, flipped on the landing light, and boom, back up to 14.2.
I'm going to try a Different voltage regulator tomorrow, to see if that might be the culprit.
 
Hunter said:
Zeftronics has been less than helpful in the customer service department, I've talked to them once out of @5 phone calls/messages.
Click to expand...

I had the exact same experience. After spending an enormous sum on their product back in 2014, I expected better.
 
Hunter said:
Thanks for all of the ideas/advice. I checked all of the wires that I could, and only had .03 ohms on the worst one, so I don't think that's it. Zeftronics has been less than helpful in the customer service department, I've talked to them once out of @5 phone calls/messages.
The issue continued on a trip this weekend, one of the times, I let it go down to around 11.8V, couldn't take it anymore, got nervous, flipped on the landing light, and boom, back up to 14.2.
I'm going to try a Different voltage regulator tomorrow, to see if that might be the culprit.
Click to expand...

One thing to remember when your are checking resistance on the wires, one strand of wire making contact is enough to give you a low ohm reading but may not be enough to carry the load to make the system work. Corrosion and lose connections can many times also pass a simple resistance check. A voltage drop test might be more appropriate. (Disclaimer, I'm only a lowly marine tech/small business owner, not an A&P so my thoughts could be completely out of line. Certainly someone will explain why shortly.)
 
You must log in or register to reply here.
Back
Top