Generator Problems Again

[Bryce]

Our earlier success getting the generating system working corretly by replacing the 10 month old voltage regulator has only been temporary.
It has run Ok for about 20hours but last week the aircraft battery was discharged when someone flew it with both the landing and taxi light on.
They returned to base and landed by light signals from the tower !

Following a battery recharge the generator light is now refusing to extinguish as the RPM rises but it will eventually after approx 5 mins ground run.

Is it possible that removing the battery for recharge may require the system to be re-polarised ?

We have chased this problem around for years now and have a new generator and voltage regulator and I think the only other component is the master switch which I have tested for correct operation but not replaced.
Thanks
Bryce

[Bruce Fenstermacher]

Yes Bryce I believe removing the battery or perhaps the deep discharge of the battery prior could cause the generator to need repolarization.

At least it doesn't cost anything to try and might solve your generator problems and won't hurt anything if it wasn't needed.

[GAHorn]

From Page 5 of the TIC170A "Electrical System" manual:
"POLARIZING THE GENERATOR / REGULATOR: A generator of the type used on aircraft utilizes a residual magnetism in the field pole shoes in order to produce a charge. Whenever any work is performed on the basic electrical system the generator should be polarized to make sure a charge will be produced. A common defect after installing a battery, replacing a regulator, or replacing a generator is a NO CHARGE condition due to lack of proper polarization. To polarize a generator/regulator system, connect a jumper momentarily between the ARMature and BATtery terminals of the regulator BEFORE starting the engine, but with the battery connected and the master switch ON. A momentary surge through the generator is enough to correctly polarize both it and the regulator." (underline/Bold added for this thread.) The Electrical System manual is available from headquarters@cessna170.org

[Tom Downey]

It's a whole lot easier in the long run to install a alternator/regulator and charging c fron a C-150, put it all down on a 337 as per AC 43-210. send it to FSDO get it approved and end all the probs.

[GAHorn]

Tom likes Fords...I like Chevy's. I can't tell you how many times I've had members contact me after they'd gone to the expense of converting to an alternator and still have electrical system problems because they didn't address the real problem. (As in this case, a dead battery won't work with an alternator either!)
Generators are rugged, reliable, and simple. Alternators are as well...but they are $700-$900 in kit form and the Form 337/Field approval is virtually a thing of the past in the lower 48 states so the cheap conversion from the junk yards isn't always a viable option (and you're still buying used stuff that may have issues as well.)
The major advantage the alternator has over a generator is that it will charge at lower rpms...where we spend almost NO time operationally. (and where the battery will support short-term heavy draw anyway.) The major advantage of a generator is it's simplicity, type certificate approval, and it will charge up a completely dead battery after propping the engine. Alternators won't without an external source of power, and they are fragile with regard to erroneous current such as when jump-starting or using ground power units and when their solid-state regulators fail. Generators are rugged and almost impervious to such problems, (the most common requirement being a simple re-polarizing.)
An overhauled gen costs about $150-$175, while a failed alt will require double that to be overhauled (unless you can do it yourself, in which case they are both a lot cheaper.)
Unless you've got a lot of extra money lying around, I'd suggest you simply take a short piece of wire and polarize it and go flying.

[Tom Downey]

GA says,

"and the Form 337/Field approval is virtually a thing of the past in the lower 48 states"

Simply not true, I get them approved when I need to. I'v done 3 alt conversions and had no problems with the paper work..

[Bruce Fenstermacher]

Tom
I'm certainly glad to hear you are able to get this done. Perhaps it's your working relationship with your FSDO.

It has been my experience in my area that NO IA's who will consider wasting their time asking the FSDO for a field approval.

Most have enough work to keep them busy with routine approved maintenance and repair. Some feel that by doing so would bring unwanted attention to their daily shop routine.

I have come to the conclusion that just finding the IA to start the process is more than half the battle.

I don't think George is out of line by saying the process may be difficult to impossible.

[Tom Downey]

I find that many IAs are not willing to follow the guidlines in AC43,210.

I use all the part numbers from the 172 I, chaging circuit and the circuit wiring, and the FSDO excepts that as the engineering necessary. no probs yet.

[Bruce Fenstermacher]

I find that many IAs are not willing to follow the guidlines in AC43,210.

I think we agree then.

And the reason they are not is they make the same money doing approved maintenance. In fact they may make more as the time spent on the approval process might be more difficult to bill or at least collect from a customer who doesn't understand the process.

They can also bring unwanted scrutiny to their core business from FSDO inspectors.

It's been my observation that the older more stubborn IAs who are semi retired and no longer rely on the income are willing to do battle with the FSDO. They won't except that some young no nothing FAA inspector can stop them from do something that they've been doing for 40 years. And they don't care if their IA is not renewed at the next expiration.

The state of affairs of the mind set of the IAs I've encountered regarding 337 approvals is sad.

As for the FSDO inspectors I've not run into one who won't follow the FARS or ACs as long as what you want to do is in clear black and white, and they read it the same as you do. Your compass card, seat belt TSO tag and airworthiness certificate are legible and in clear view as well.

I do believe the system can work. It is frustrating for me as an airplane owner that it doesn't seem to be. I'm not being smart or funny when I say Tom, that I'm glad you are able to get this stuff done. It is a ray of hope that perhaps yours and your FSDOs attitude will spread country wide.

I use all the part numbers from the 172 I, chaging circuit and the circuit wiring, and the FSDO excepts that as the engineering necessary. no probs yet.

This is exactly the tack I would take as well. It makes sense.

[wa4jr]

I always thought that the generator would retain a residual voltage while the battery was removed for maintenance or charging and be ready to go again when the battery was reinstalled. That is supposed to be the strong point when you completely kill your battery by leaving the master on....you can hand prop and the charging will start. I've never repolarized my gen after a battery change, and the charge always seems to be just fine by the amp meter. Any thoughts George? Should I start "flashing" the generator as a matter of practice after the battery has been removed? I've got one of the Zephtronic regulators, and I am not sure which terminal is which...I wasn't the one who put it in and I know the paperwork has been recycled several times by now

[GAHorn]

The Zeftronic regulator is a different animal, and I cannot make a recommendation as to how to deal with their product. But they are very knowlegeable and helpful and you might simply call them up and ask them about it. Perhaps their regulator is your problem and they can advise you. Tell Femi I said "hi". He won't remember me, but he's a good man.
Still...It should not be difficult to polarize the system even with a solid state regulator like theirs. The largest wire coming from the generator to the regulator is the ARMature and it should be momentarily "flashed" to the positive battery post or positive battery cable where it attaches to the starter with the master sw. ON but the engine not running.
You are correct, in that the generator has soft-iron pole-shoes and should normally retain it's magnetism thru a battery change, but sometimes things happen. At least we don't change batteries often (and when they are discharged, there's usually a small residual charge in them to keep things working after propping the engine...just not enough to excite an alternator.)

[jrenwick]

Zeftronics has troubleshooting guides that you can download from their web site. Go to http://www.zeftronics.com. On the left hand side of the home page, look for "Troubleshooting." Click on that, then click on "Delco-Remy," and then "14 Volt Type A." That will get you to the writeup on their regulator for generator systems. Its instructions for flashing the field are as follows:

HOW TO FLASH THE GENERATOR’S FIELD:
1. With the engine off, disconnect the Generator
Controller (GCU) / Regulator
2. Ground the Field wire removed from the GCU
and turn on the GEN FLD switch
At the GCU: Touch the battery wire to the generator’s
armature wire 5 times for 3-5 seconds. Caution: Take
safety precaution to prevent being hurt by electrical
sparks generated by touching the two wires.
3. Connect a voltmeter between the generator’s
ARM and ground. At 1300 RPM, the generator
output or residual voltage should be >+1.6V.
ARM Voltage ________V @ _________RPM

Best Regards,

John

[GAHorn]

Zeftronics has troubleshooting guides that you can download from their web site. Go to http://www.zeftronics.com. On the left hand side of the home page, look for "Troubleshooting." Click on that, then click on "Delco-Remy," and then "14 Volt Type A." That will get you to the writeup on their regulator for generator systems. Its instructions for flashing the field are as follows:

HOW TO FLASH THE GENERATOR’S FIELD:
1. With the engine off, disconnect the Generator
Controller (GCU) / Regulator
2. Ground the Field wire removed from the GCU
and turn on the GEN FLD switch
At the GCU: Touch the battery wire to the generator’s
armature wire 5 times for 3-5 seconds. Caution: Take
safety precaution to prevent being hurt by electrical
sparks generated by touching the two wires.
3. Connect a voltmeter between the generator’s
ARM and ground. At 1300 RPM, the generator
output or residual voltage should be >+1.6V.
ARM Voltage ________V @ _________RPM

Best Regards,

John

Their instruction to "turn on the GEN FLD switch"... is actually an instruction to turn on the Master Switch. (In our airplanes the Master Switch is a two-circuit switch. One circuit grounds the battery relay mounted on the battery box and thereby activates the electrical system, and the other circuit connects the gen FLD wire to the regulator's FLD terminal (and which on original regulators is internally grounded.) Therefore their instruction to disconnect the regulator makes it necessary to instruct you to ground the gen FLD terminal directly to the airframe, ... and their instruction to activate the "GEN FLD" switch is a misnomer, since what they really mean is for you to turn on your battery so it can be used to "flash" the field (i.e. polarize the generator-field.)
On original regulators simply turn on the Master and momentarily connect the regulator's BATtery and ARMature terminals. Perhaps Zeftronics is concerned about their solid-state circuitry if it is connected while polarizing the generator,.... or perhaps they are merely wish to avoid giving the impression that solid-state regulators need "polarizing". (Unlike original vibrator-point regulators, they don't. The Electrical System Manual method polarizes both gen and reg simultaneously by 1-turning on the Master, 2-momentarily connecting the regulator BATtery and ARMature terminals. That method presumes a good cockpit master switch/connections, as it does not bypass a possibly defective gen FLD circuit like the Zeftronics method does.)

[Bryce]

Hello
Following the advice we polarized the generator/regulator and during the engine run the generator warning lamp extiguished at 1500rpm and the low voltage lamp extinguished at approx 1800rpm .
We did not have chance to fly the aeroplane staight away so it sat for a few days until this Saturday.

For the first flight everything appeared normal although the generator lamp took some time to extinguish during the engine power checks.

On engine start for a subsequent flight the generator lamp again refused to extinguish.The generator fuse appears ok so it seems we are back to some more head scratching.
I am not sure where to go now and have considered the battery condition but it has sufficient charge to start the engine so do not consider it to be at fault.
I may try a further repolarization but I am now not certain this is the problem.
Bryce

[GAHorn]

Bryce, there is something else going on. A Zeftronics regulator will normally bring a good generator online around 1000-1100 rpm. A good generator with an older type vibrator regulator will come on about 1100-1300 rpm.
Either you have a defective regulator, generator, ....or other wiring problem.
A quick way to determine if your generator is good is: disconnect the lead from your FLD terminal of the generator, and with a short jumper wire connect the gen FLD terminal directly to airframe ground. The generator should give a healthy charge at 1400-1600 rpm. If not, then either the gen is defective, or the aircraft charging circuit is defective. (In the latter case, inspect the ARMature circuit wiring between the gen ARMature termina and the regulator ARMature terminal, and the circuit between the regulator BAT terminal and the battery.)
A good generator test using the above method leads us to suspect the regulator.
However, if your gen/reg are both good:
Your generator is connected to the regulator thru the Master Switch. (Not the relay on the battery box, but directly thru that cockpit switch, which has two circuits going thru it....one circuit grounds that small wire leading from the third terminal of the battery-relay on the battery box,... and the other circuit connects the generator FLD terminal (the small one) to the regulator FLD terminal.
Either that circuit is not clean/bright/tight... or your regulator is not properly grounded to the airframe (usually thru it's case and mounting bolts and/or dedicated ground-strap)...
...or your generator ARMature circuit is not intact (clean/bright/tight) in it's connection between the gen ARMature terminal-to-regulator ARMature terminal.
Carefully check out those wiring circuits, then if things still aren't working for you, get very suspicious of your generator itself. (brush tensions/commutator contact and/or internal field windings are suspect in my mind.)
I'll bet a call to Zeftronics will bring you an offer to test that regulator from them...perhaps your generator can be checked locally, but if not, try http://www.aerotechlou.com/