pk911

Thank you! Good advice, I will check availability of the coupler in Germany. Mine has 17 years and 1200 hours now. This part was inspected last week and found satisfactory by the shop.

The shear coupling was simply to old. These couplings become brittle (and fracture prematurely) given the effects of age and environment. It hasn't anything to do with the load in my opinion. If load is to high you will see negative load that is taken from the batteries. That should be avoided. The shear coupling can handle the full draw from the alternator. So I will mine replace every 10 years now. It was 17 years when broken.

Hello everybody, now after nearly one month some updates to the alternators mystery: Main alternator field voltage check on F1 positive but without current flow. Coals? The main alternator was VERY difficult to remove. Two bolts above no problem, one left down a catastrophe. The Continental guys must have dwarf hands... After removal and sending to a special repair shop they detected both coals were down to the metal and scratched the alternators axis. So the alternator has to be replaced. The alternator had about 1200 hours without service. Continental recommends service every 500 h. It's worth doing so! See first 3 pics below! The 20A standby alternator from B&C was very easy to remove. Just 4 screws. Shear Coupling was broken. A $42 item, that can decide over your life! This part should be replaced after a certain amount of time. Mine was still original and broke after 18 years! See pic 4. B&C is very cooperative! Top specialists and very quick delivery! Super perfect! Thank you TJ! My shop will going to install the alternators in the upcoming days. In future I will have a closer look at my subsystems and will prompt more actively my maintenance shop for such details. These can decide about your life. Fly save and have fun Peter

What happens later? How did you solve the problem?

Thanks a lot! Best regards and nice weekend!

Does anybody have a detailed cabeling layout of the Ovation 2 DX? I wonder how main alternator and standby alternator get voltage for delivering power. Maybe same source? Maybe without a dividing diode? Thanks in advance! Peter

and you are increasing load to the starter for you turn an active generator with alternator on. You only want to turn the engine to get it started

I can tell you after failure of main and standby alternator the system is working in full if you have good batteries and the corresponding fuses pushed. I could lower the gear without problems. Thanks Concord batteries!

Thank you Matthias, I use the standard POH ground procedure every time I depart IFR. In this case everyting worked well on the ground and even after the main alternator failure in the air. Switching back and trying to bring the main alternator back to life without success and then back to standby alternator killed the system. I have to find out why! I plan to examine the airplane with my shop next Monday and keep you all informed. Have a nice day! Peter

Thank you! Please look at my answer to Jerry 5TJ. When trying to get the standby working again, all breakers are in. ALL the 70 amp bus selector, too. Maybe this caused some trouble. But some members go with the standby and nearly full equipment. I wonder if the main alternator switch must be OFF before the standby alternator can be put in work? You hit the point with your question concerning a special procedure for starting the back-up alternator! POH says nothing special. Best regards from Germany! Peter

Thanks for the details. Yes, I checked the circuit breakers, before first pushing Alternate Bus and after the 1st attempt to get the main alternator back. They were all in. After not getting any alternator back to work I pulled some breakers to redurce battery load.

My Mooney is a 2004 Ovation 2 DX. Yes, the second battery is worth every penny! I used both on way home today. Two good batteries can save lives. And, yes it's a 20 amp alternator and I didn't pull the fuse! But when switched on the first time the voltage was 30V and indicated load of 2 amps.

Hi guys, today I was on a trip home from southern France to Germany. IFR FL090, clouds from 2000 to 6000 and complete fog below for about 300nm. Suddenly the generator lamp flashes and the display reports -8 ampere. My generator obviously stopped working. I pushed the standby generator, the indication changed to +6 then +3 amperes and everthing seemed good. NOW, never touch a running system! I switched standby off and alternator switch off and alternator switch on again. Nothing happend. Then I returned back to the standby alternator again and NOTHING happend! It has stoped working too! I communicated with ATC switched of nearly everything beside transponder and my handheld radio and shoot an approach 1 hour later in a fog free area and returned home VFR with remaining battery power. 2 good batteries! Does anybody have an idea what caused two alternators to stop working? Thanks, Peter

Thank you all for good advice! Took great steps the last 24 h! Checking the diodes is quite easy. Just remove all three fuses and you can check at least the depicted half of the rectifier which was o.k. Next question is the capacity of the fuses. Mine were all 15A. SB M20-275 shows 10A. I'm quite sure nobody changed the fuses. Which is right then? 10A or 15A? Battery voltage should be an important checklist entry. Everything below 23V could lead to blowing the fuses. AND there ist now indication to the pilot that the fuse is blown. I my case battery #2 was about 21V, I started with #1 guessing #2 will be charged during flight. Nothing happend. In case of emergency I would have only one battery! The only quick solution would be starting the engine with #1 and switch over to #2. This arises the question if the alternator should be switched of before switching over the battery with running engine because of voltage peaks during switching!? And you should ever have some 15 Amp fuses with you! Best regards and nice day! Peter

Thank you Clarence! That's it! I regulary switch the batteries before each flight. Due to bad weather in Jan + Feb I didnˋt fly lot. Battery quite low. After engine start high amps at ampere meter. Maybe 1st time blows #2 and next flight #1.Thus only charging the active battery. To avoid I try to keep the batteries up to avoid high recharge amps. Is there a possibility for more S&MM? Thank you. Peter