196Mooney 20E

[PJ_M20E]

Hi everyone, I'm a relatively recent new Mooney owner and am trouble shooting electrical system for first time...well first time in mooney and airplane for that matter.  

I started to check polarity of generator and ran into some issues and questions that I'm hoping someone could provide some insight on.

First question will really show I don't have a lot of knowledge here.

 

1.  Generator (delco) has two wires coming out of it.  The one marked "A" with the heavier wire which I assume is the output from generator and a small wire that I can't see a label on  which is probably a ground or field wire.  I was very surprised to see both wires went to ground (39 ohms) with master switch off is this correct?  If if is correct, where is the ground VR or master switch?

 

2.  Where is the generator field switch noted in steps below?

3.  Should I need to flash generator can I use a car battery and jumper cables, or should I remove planes battery and bring it to front of plane?  or find hot line in engine compartment?

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 

[jwilkins]

Can you back up just a bit and give a little background on why you are trouble shooting the generator?

Is it low voltage, no voltage, or no amperage output? Have you checked the regulator?

My 62 C had a generator which was really pretty bullet proof; much more so than most alternators I've had, but not much output at low RPM / idle. The only difficulties I had with the generator were 1) the braided wire from one brush broke, and 2) points on the old mechanical regulator got carboned up. BTW when the brush's braided wire broke the shop AP couldn't get one for a week from the MSC so he put in a 'temporary' Delco brush from NAPA. It looked identical (except the wire was not broken) and we never did get around to replacing it with a certified part.

It's too bad the generators are such a pain to R&R or you could get it bench checked at your local auto parts store (I'm not suggesting a repair or OH, just a bench check). If you have a full service generator / motor repair shop in town they may be able to check the regulator for you, and it R&Rs a lot easier than the generator.

I'd visually check for electric issues (good ground connections, loose wires, burned points in the regulator, brushes OK, etc) as a first step. 

I learned about aircraft maintenance from a grouchy old AP/IA who took great delight in abusing me while he taught me about aircraft repairs, let me work as his shop boy / technician for free, showed me how to do an annual inspection, let me buy some rigging tools for him that he didn't have, and checked and signed off work I did on my plane under his supervision. Eventually he let me work for free doing electrical and radio work in his shop. I also put in several of the Mooney upper door pin SB retro fit kits under his supervision. Never touched an engine or flight control, but got to watch and hold wrenches. I paid him the normal shop rate for work he did for me (except for one year when I traded a Mercury Station Wagon for an annual inspection), and always considered it a bargain.

If you can possibly find someone to work with you'll hopefully be as amazed as I was how some of these guys can frequently diagnose problems from 10 feet away. Apparently if you spend 50 years working on planes you eventualy see some of the same issues more than once. I could spend hours fussing with issues that he could (sometimes) diagnose in a few minutes

I still have the service manual for 62 - 67 if you need any particular pages scanned let me know by PM.

Jim

 

[PJ_M20E]

I'm hoping to find my own A&P to work with and  have one lined up to at least lookhelp with current issue.  Hoping to learn airplane and maybe save some money over time or pursue A&P which is why I'm looking into it.

A little back ground, I've only had Mooney a few weeks and have only minimal experience as aircraft owner with maintenance...although generally technically / mechanically very capable just haven't delt with airplanes.

The airplane is 65' 20E with IO-360 engine. Aircraft was annualed in Dec and check out fine.  The plane was ferried from Ca to Phoenix around Christmas with no issues reported.  First flight I went to take it up the ammeter indicated 0 charge durin runup. After much time spent turning things on/off I started monitoring battery voltage which by now was down to 10.3V and did not change whether engine was running idle or 1500RMP.  I took battery home and charged it and it holds voltage thru several starts and power checks.  I don't see any loose or broken  or damaged wires. I checked polarity of generator today and think it is correct.  I do think I have a possible short between generator output and ground.  My suspecion is that there is some short at VR but won't be able to isolate it until I unhook wire from VR.

 

any thoughts appreciated...

[garytex]

There are a couple of books out there that can be helpful.  "Light Plane Maintenance" is one that I can remember.  Truly ancient Aviation Consumer articles, from the 1980's have nice how to articles in them.

There was another one the title was "Owning and Maintaining...then some aviation words to that effect.  Search Amazon.  

The point is to learn enough that you are able to actually service your wheel bearings, spark plugs, oil and filter, etc without screwing it up, and to be able to converse with your mechanic from a reasonable enough base of knowledge to understand what he is talking about.  

All the systems on an airplane are blood simple, and easy to understand.  Not like recent cars which are way to smart to be able to figure out.  Once you start changing your own oil, and spending some time looking at your engine, you will feel more comfortable with your plane.  You may not have the most knowlege at first, but nobody cares about your plane like you do.  Go for it.

Gary 

[jetdriven]

You need a proper Mooney M20E service and Maintenance manual and an Illustrated Parts Catalog.  You cannot properly work on a Mooney without one. 

http://www.eflightmanuals.com/search/searchResults.asp

Manual 101 is your most current S&M

Manual 203 is your most current IPC

[PJ_M20E]

Thanks for everyone's input...narrowed flaw to generator.  To be cont'd...

[PJ_M20E]

I was looking at how to take generator out today, do you really need to removal lower cowl? It appears to be a time consuming under taking.  I'm hoping there is a trick....

[MooneyMitch]

Quote: PJ_M20E

I was looking at how to take generator out today, do you really need to removal lower cowl? It appears to be a time consuming under taking.  I'm hoping there is a trick....

[N601RX]

Removing the landing light will give you another hole to reach through.

[MooneyMitch]

The greatest obstacles in attempting to access certain items in the bottom area of the engine compartment are the intake tubes and the exhaust pipes.  When those are not in place, it's like WOW, this is great!  This includes access to the 6 bolts that secure the fuel injection rubber boot to the cowl intake are box.  YIKES, what a relief!!

[PJ_M20E]

I'll have to try again to get swivel rachet on one side of alt...didn't get that far.   I don't see an area big enough to get generator out unless maybe with fuel injection boot completely removed maybe it will out left side.  Will try to getit out Thursday, thx

[moodychief]

Quote: PJ_M20E

Hi everyone, I'm a relatively recent new Mooney owner and am trouble shooting electrical system for first time...well first time in mooney and airplane for that matter.  

I started to check polarity of generator and ran into some issues and questions that I'm hoping someone could provide some insight on.

First question will really show I don't have a lot of knowledge here.

 

1.  Generator (delco) has two wires coming out of it.  The one marked "A" with the heavier wire which I assume is the output from generator and a small wire that I can't see a label on  which is probably a ground or field wire.  I was very surprised to see both wires went to ground (39 ohms) with master switch off is this correct?  If if is correct, where is the ground VR or master switch?

 

2.  Where is the generator field switch noted in steps below?

3.  Should I need to flash generator can I use a car battery and jumper cables, or should I remove planes battery and bring it to front of plane?  or find hot line in engine compartment?

 

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 

 

[MooneyMitch]

Quote: PJ_M20E

I'll have to try again to get swivel rachet on one side of alt...didn't get that far.   I don't see an area big enough to get generator out unless maybe with fuel injection boot completely removed maybe it will out left side.  Will try to getit out Thursday, thx

[Steve65E-NC]

PJ, I would first start at the battery and take the heavy wires down a single screw or bolt node at a time cleaning and polishing all mating electrical surfaces right around the heavy circuit and generator  circuit.  You may also find any loose terminations etc.  I believe this needs to be done wheather you have a generator problem or not.  I am starting this on my 65E and plan to reassemble each clean node with a dab of silicone dielectric greece.  I have about a .7 voltage drop between the main bus and the battery and hope to improve it in this way.  My 65E was converted to alternator long ago and you might want to consider that at this time before spending much on the Generator.

[PJ_M20E]

Got generator out, wasn't as bad as I thought to drop lower cowl.  Bearings shot...full overhaul required.  Wiring otherwise seems good.  Want to clean engine compartment up good next week any suggestions?

[jetdriven]

i'd replace it with an alternator.   Almost the same money at this point. Generators are so heavy, and dont charge at idle.

[Ned Gravel]

I too am replacing my generator for the Plane Power conversion one next month during my annual at Tri City.  Its a little lighter than the generator and I won't be popping fuses on climb out into IMC because I was taxiing for so long at too low a power setting to charge the battery.

[PJ_M20E]

I decided to stick with generator until next time...  It should work out to less than have of cost of alt conversion and historically plane has had no appreciable electrical sqwaks.  Of course if I end up pulling it out again next year...I won't be ashamed to acknowledge you told me so.

[Ned Gravel]

Quote: PJ_M20E

I decided to stick with generator until next time...  It should work out to less than have of cost of alt conversion and historically plane has had no appreciable electrical sqwaks.  Of course if I end up pulling it out again next year...I won't be ashamed to acknowledge you told me so.