Generator

[jmbrwn]

During my flight this evening, my generator light came on. Sure enough, the gauge showed zero. This was the second leg of a short hop...no problems on first leg. Is there anything I can trouble shoot that could be the problem besides generator?...maybe voltage regulator?

[GAHorn]

1. Confirm your fuse or circuit breaker is good. INspect the connections at your generator Field and Armature terminals, and Inspect the connections at your regulator BATtery, ARMature, and FieLD terminals.
2. Re-Polarize your generator/regulator by A) Turn your Master Switch - ON, B) WITHOUT running the engine BRIEFLY touch a jumper wire to the regulator BATtery terminal and the regulator ARMature terminals. Then without turning the Master off, start your engine and run it at 1800 rpm to see if your generator is back online. If so, you're finished. If not....
3. Clip a jumper wire onto your regulator FieLD terminal and the other end of the wire to a good airframe GROUND. Run the engine at 1800 to see if the generator charges. If so, then the regulator is bad.
4. If item 3 still shows no charge condition, then clip the jumper wire directly to the generator FieLD terminal (this is the small terminal on the generator case) and the other end of the wire directly to a good airframe GROUND and run the engine again at 1800 rpm. IF a charge now occurs, then the fault was the wiring between the gen/master/regulator. (Remember that this wire passes thru the cockpit Master switch, so it's possible that switch has failed, and to determine that it will be necessary to use a meter or continuity tester to confirm circuit continuity.)
If still no charge, you have a faulty generator. Repair it or exchange it for a rebuilt one. (I've had good service from AeroTech of Louisville, 800-634-0190)
5. For a more detailed description of the generator charging system, and the entire Cessna 170 electrical system, including Troubleshooting and wiring diagrams, contact TIC170A headquarters@cessna170.org and ask the secy to sell you the Cessna 170 Electrical Systems Service Manual. $20 cheap (member price).

[jmbrwn]

A wealth of information! Thanks much, Gahorn!

[Bruce Fenstermacher]

Hey Jim
Just like to add that running your aircraft for short periods of time (1 minute) with the jumbers in place the way George describes will not hurt your aircraft or systems but since you are essentially eliminating the regulator with these tests you wouldn't want to run it for a long period which will cause damage.

Also when you "flash" or repolarize your system as outlined in #2 there will/should be a spark.

I have the Cessna 170 Electrical Systems Service Manual and it is good and it would be great if you supported the association. The same information is available but maybe not in as complete form and specifically for the 170 from sources like the Cessna 100 series service manual.

[jmbrwn]

Thanks for the info, Bruce. I talked to Velvet today and ordered the Electrical Service Manual, along with some other things I wanted.

[zero.one.victor]

First of all, what's this electrical service manual? Is that a new Assn publication? I hadn't heard of it til now.
Secondly, George, I would sure like to see you write an article about this electrical troubleshooting business for The 170 News. You've posted some other real good tips about diagnosing & solving electrical problems in the past. Please see my current post about the (apparent) lack of articles for The 170 news.
This is the kind of article I really like to see in The 170 News. I keep all my old ones, plus if an article is really good I zerox it & put the copy in with my airplane manuals. It's a lot easier to me to look up my hard copy than to search thru a million posts online. It'd be neat to have all the electrical stuff in one article, too.
I think a lot of other guys are like me--electrical idiots! So how about it?

Eric

[Bruce Fenstermacher]

First of all, what's this electrical service manual? Is that a new Assn publication? I hadn't heard of it til now.

We like to keep the North West Members, especially those whose aircraft have 2 wing struts, in the dark.

Eric
I'm sure George will post better details but here is what I remember from the Tehachapi Convention.

Several association members have put their heads together in an effort to write or gather information into a 170 specific service manual. It's to be done over five years. The first chapter "Electrical Systems" was completed and distributed to attendees of the maintenance forum at Tehachapi. It is a work in progress. I believe the intention is to finish the other 4 chapters and distribute them at the next four conventions as a bonus for attending the convention. As George said they are available to everyone at a modest cost from HQ.

I like mine and am happy to have it. When the project is completed it will be very nice. As I said in an earlier post most of the information is available from other sources as there probably hasn't been any change to generator/regulator operation in 50 years. The manual is an attempt to collect the available information and add missing pieces and in some cases made more 170 specific then publish it in one place

[GAHorn]

The Electrical Service Manual is Part ONE of a FIVE part Dedicated Service Manual specific to the Cessna 170 series. No such manual has ever been developed. (Cessna only produced a generic "100 Series" manual that barely mentions the 170, and devotes the majority of it's attention to 150/172/182 aircraft. Contrary to popular opinon, the 170 is NOT just a 172 on conventional gear. It has many significant differences regarding service and maintenance.)

Since there is no 170 Service Manual, I was approached to produce one. Section One is the Electrical Section, it is available in both Spiral-Bound Manual and CD formats. The cost of the manual goes entirely to TIC170A to offset printing/production and to support TIC170A.

The Introduction page of the manual tells the story of the origins of the manual.

It was in the lobby of the hotel during the 2001 Texas Christmas Party held in Nacogdoches that TIC170A Historian Cleo Bickford approached me. If I hadn’t been so overwhelmed by the warm welcome and atmosphere of all the fellow Cessna 170 owners present I might have been more alert to the twinkle in his eye. He was on a mission and I didn’t realize it.

Cleo, charter member number C42, being an accomplished aviator, experienced aeronautical engineer, Cessna 170 owner, and devoted promoter of TIC170A, had long observed the painful lack of a service manual specifically for the 170 and made it his goal to address the issue. A manual had been contemplated for many years but had never been brought to fruition and Cleo apparently decided there would be no further harm in soliciting the services of yet another procrastinator. The difference this time was, …Cleo had his “don’t even THINK about telling me no” charm turned fully ON! I was caught completely unawares. In all fairness, he did allow me to think it over before committing to the project. Those who know Cleo well can appreciate what that truly means. His quiet, well-respected manner plays upon the conscience until the decision was made: I WILL complete the project, no matter how long it takes!

This is the first attempt at a service manual for me, so I ask forbearance if it appears less than complete. It is very much a “work in progress”. This first section is dedicated to the electrical system, and subsequent sections will be presented at upcoming convention seminars until the entire manual is complete. As new material (and authorship technique) is developed, this section will be revised and amended. The complete manual encompassing all systems is expected to be a five-year project. A person attending all five convention seminars will have obtained a complete manual, and helped influence the final products outcome.

Wherever possible part numbers have been included in the text for convenience’s sake. Be aware that part numbers may be superceded at some point in time and be certain to confirm any part requirements. An attempt has been made to help the owner with unsophisticated repair and troubleshooting techniques. Some of those activities may not meet the FAA’s definition of “preventive maintenance” and therefore undertaking such actions should be considered carefully. By all means, do not violate the law, or good operating procedures.

Several sources have been consulted in preparing this manual including but not limited to manufacturer service manuals, overhaul manuals, and FAA Advisory Circulars (especially AC 43.13-1A “Methods and Materials”.) Much of the information herein is the result of years of experience gathered from many individuals, most of whom will go unfairly unrecognized. To my friends and fellow aviators I apologize if I’ve “borrowed” your ideas too readily. I hope you take consolation in seeing them put to good use. If as the reader you find something to correct or improve the manual, please contact me and let me know for inclusion in future revisions. None of the information in this manual is intended to replace manufacturer or FAA approved methods and practices. This manual is intended only for the purpose of furthering the understanding of maintenance issues as regards this airplane. Neither The International Cessna 170 Association nor the author makes any representation as to the fitness of purpose or the suitability of the information contained herein. Use it at your own risk.

Having given to disclaimer, now please join me in the pleasure of dedicating this manual to the person who I credit as the real motivating force in its production:
Cleo Bickford, C42, Historian, TIC170A, without whom it would never have been started, and doubtless with whom it will never be finished. ;Þ

George Horn
Parts/Mx coordinator, TIC170A

The Topics/Contents of the Electrical Section include:



BATTERY AND EXTERNAL POWER SYSTEM
Battery
Battery Box
Battery Solenoid.
Master Switch.
Ground Service Receptacle.
Troubleshooting the Battery System
Removal and Replacement
Cleaning, Testing, and Charging…………………..
Battery Box Removal
Battery Box Maintenance……………………..…….
Battery Solenoid Replacement

GENERATOR POWER SYSTEM.
Generator
Radio Noise Capacitor
Generator Warning Light…………………………...
Ammeter
Removal and Replacement of Generator
Polarizing the Generator/Regulator
Voltage Regulator…………………………………...
Removal and Replacement
Troubleshooting the Generator/Regulator ……..
Generator Tests, Repairs, and Adjustments
Simple Generator Test……………………………...
Generator Short Test
Voltage Regulator Repair and Adjustment
High RPM Gen OnLine Speed
Adjustment of Voltage
Adjustment of Current
Isolating Too Low/High Charge……………….….
Inspecting Regulator
Regulator Point Cleaning

Engine Starter…………………………………….…
Starter Electrical Circuit
Starter Lever/Cable Adjustment

AIRCRAFT LIGHTING SYSTEM. ,
Landing and Taxi Lights
Navigation Lights…………………………………..
Navigation Lights Flasher.
Rotating Beacon.
Interior Lights Map Light and Dome Light,
Removal and Replacement of Dome and Instrument Lights
Compass Light
Removal and Replacement of Navigation Lights

PlTOT AND STALL WARNING HEATER………..
CIRCUITS
System description
Removal and Replacement of Pitot Heater

STALL WARNING
System description

TROUBLESHOOTING THE ELECTRICAL SYSTEM...
EXAMPLE: Stall Warning troubleshooting

Table of Contents cont’d


Electric Wire…………………………………………
General
Aircraft Electrical Wire

Wire Gauges and Ampacity Chart..………...……
Battery Cables
Splices
Open Wiring…………………………….……………
Heat Precautions
Protections Against Chafing
Stripping
Terminals

Attachment of Terminals to Studs……………….
Bonding Jumper Installations
Corrosion Prevention
Ground Return Connections
Current Limiters


Wiring Schematics

Electrical Schematics
SNs 20267 THRU 26372
SNs 25373 THRU 26995
SNs 26996 and ON
SNs 26996 and On – Inst Pnl

Electrical Wiring Diagram Identification
(Wire ID, Length, Sizes)

Appendix EL (Illustrations)


Ground Service Plug and Early Battery Solenoid (Relay)….EL 1

Late Style Battery Solenoid (Relay)

Battery Solenoid (Relay) and Master Switch Circuit………...EL-2

Landing Light Adjustment

MultiMeter…………………………………………………………...EL-3

Test Leads

Generator Motor Test Schematic……………………………….EL-4

Test for Generator Short

Voltage Regulator………………………………………………….EL-5

Test 1 to Confirm Regulator Ground

Test 2 to Isolate Regulator

Test 3 Cut Out Relay (Reverse Current Relay)……………..EL-7

Starter Cable/Lever Adjustment
=================

[jmbrwn]

Gahorn...just wanted to let you know how it turned out. Today was the first time I've had to go out to the plane to trouble shoot it. I had received the Electrical System Manual from Velvet and read over it...very good job to whoever put this together...the first step after checking all the connections was to re-polarize the generator/regulator. Well, that solved the problem!

My question now is what caused this to happen?

Thanks to all who shared their input.

[GAHorn]

The person who put it together was the same person who wrote the introduction, and I'm sure he'll appreciate the compliment!
Hopefully it's a helpful document.
Generators (and/or regulators) can lose polarity for a variety of reasons. The most common is inactivity or a battery change-out. (Although the latter is sometimes a puzzle: Was the battery determined to be bad because it wouldn't take a charge? ....or because it wasn't receiving a charge? Sometimes batteries are declared defective and then when they're changed out, the new one doesn't seem to hold a charge either until the owner realizes the problem is the charging circuit.
The worst cases are usually airplanes that don't have an ammeter or voltmeter and rely only on a generator warning light. (Just because the lamp is not illuminated,...does that mean all is well? Of course not.....the lamp could simply be burned out or the regulator circuit burned up!)
A momentary reversal of polarity has been blamed for lost polarity. This is sometimes blamed on a slow or sticking regulator reverse-current relay, but I'm not entirely convinced of that theory.
In any case, loss of polarity CAN occur, and you now know the fix!
Congratulations!

[zero.one.victor]

Well, George's generator troubleshooting information (second post, above) came in handy today. A friend's Pacer wasn't charging. He removed the generator & took it to a local (pilot-owned) automotive/marine electrical shop. The guy pulled it apart, found a broken brush wire, replaced both brushes (worn out), cleaned up the armature (& in fact the generator in general), bench-tested the generator, tested & adjusted the regulator: all for $30, pretty good deal, I thought.
My buddy reinstalled the generator & regulator and guess what, still not charging. I helped him today, we jumpered the regulator field terminal to ground, etc etc-- no good. So I decided to check the wiring between the generator & regulator. Started out checking the continuity between the regulator "gen" & generator "A" terminals-- good. So good, in fact, that we even had continuity between the regulator "gen" terminal & the generator "F" terminal! Huh? OK, let's disconnect the wire at each end, from the regulator "gen" & the generator "A". Double huh?-- no continuity. Upon further investigation it turned out he had reversed the wires at the generator-- the generator "A" was hooked to the regulator "F" and vice versa. DOH!!! Switched the wires back & everything worked great. Just goes to show ya that it's usually something simple.
Now how about troubleshooting an alternator-- can you ground the regulator "F" terminal (or whatever the equivalent is for an alternator system) & check it the same way? The 60-amp alternator conversion was done by a previous owner-- I'm sure that it's a different regulator than the generator used, but I'm not sure if it's marked "batt" ,gen", and "F" like the regulator on my buddy's Pacer. I need to eyeball the regulator terminals & see how they're marked. If they're marked the same, seems like it must be doing the same thin inside & therefore jumpering it the same way would have the same results.

Eric

[jrenwick]

Now how about troubleshooting an alternator-- can you ground the regulator "F" terminal (or whatever the equivalent is for an alternator system) & check it the same way?

Eric,

There are good troubleshooting guides for both generators and alternators on the Zeftronics web site, http://www.zeftronics.com. Follow the "Troubleshooting" link on the left side of the homepage. They're written for Zeftronics controllers, but they're helpful for other kinds of regulators as well. Have fun!

Best Regards,

John

[zero.one.victor]

Thanks for the Zeftronics link, John. The troubleshooting page I was able to download seemed to be Zeftronic-specific, with separate controller & over-voltage boxes. I tried to download the troubleshooting page entitled Delco-Remy but my computer couldn't make heads or tails of it so it "suppressed further errors". In other words, it dummied up (like I do in similar circumstances!).
I took a look at my regulater: Auxilec Inc p/n VR600 (aka Cessna p/n C611001-0201) serving a 60 amp Ford/Cessna alternator. Four terminals:
I (un-used), A (big wire), S (medium wire) and F (small wire). What do these initials designate? As I understand it, an alternator has a rotor & a stator instead of a field & an armature? Those initials don't seem to match up. I need to see if Auxilec has a website, and/or trace out my wiring further. I was in a hurry when I looked at it yesterday.

Eric

[jrenwick]

For what it's worth: the Zeftronics alternator controller also has terminals labeled "I", "S", "A" and "F". In their documentation, the "I" terminal goes to an optional Low-voltage/Overvoltage indicator light (so maybe "I" stands for "Indicator"?).

The "S" terminal receives power from an external overvoltage sensor, and it pulls an internal relay that connects the "A" terminal to the rest of the controller to give it power. So it looks like you turn on the controller by applying bus voltage to the "S" terminal, and if the bus voltage is too high, the overvoltage sensor will protect the controller's solid state components by opening the "S" circuit.

The "A" terminal of the controller goes to the "B" terminal of the alternator, which is also connected to the battery through the ammeter and master relay. It supplies power to the control unit and, indirectly, to the alternator field.

The "F" (field) terminal of the alternator is connected to the "F" terminal of the controller. The controller regulates the alternator's output by energizing and denergizing its field winding with current it gets from its "A" terminal.

I don't know if these terminal functions are standard for all alternator controllers, but if they are (that would make sense!), then the Zeftronics sheet may actually be helpful. I'm referring to the "Cessna 14 v Alt Type B" sheet under "Troubleshooting" at http://www.zeftronics.com. There are also Type A alternators, with different circuitry -- you have to first figure out what you have.

Eric, the Delco-Remy troubleshooting sheet you couldn't download is for generator systems. If you still want it, send me an email (jkr@iphouse.com) and I'll send you a copy. Its file name on the Zeftronics site has funny characters that your browser may have choked on.

Best Regards,

John

[zero.one.victor]

Thanks, John. I'll go back to the Zeftronics site & look at that Cessna 14v alt type B info. If my ignorant computer will open it, that is. It's Adobe Aerobat,I don't know why it's giving my computer a hard time...

Eric