Search the Community

I have a 77 201 and have been experiencing an intermittent electrical problem for some time. When this issue occurs, maybe every 3rd or 4th flight, the alternator will stop charging leaving the plane to operate on battery power. Usually when I notice this I can recycle the master switch a couple of times until it comes back online. Because it is so intermittent, it has been difficult for my A&P friends to diagnose. We attached a wire to the field wire connection at the alternator and ran it up into the cockpit. I attached a volt meter to it so I can monitor what is going on when this happens. (Trying to determine if the problem is the alternator or voltage regulator). Yesterday, I went to fly and during my run up on the ground I was turning on the landing light, pitot heat and anything else to put a load on the electrical system. During all this my field wire voltage was around 8 volts and bus voltage was around 14.1 volts. I looked away for a few seconds to attend to something else and when I looked back I had 0 volts on field wire and 12.3 volts on the bus. Recycling the master switch brought everything back to normal operation. I haven't had a chance to share this information with my A & Ps but wanted to put this info on MooneySpace to see what the consensus was here. Your input will be greatly appreciated.

About half way from KBTL to KOWB to attend a MAPA PPP session, the alternator field circuit breaker popped. I shut the field switch off, and reset the breaker, turned the field switch back on. In about 5-10 minutes the breaker popped again. I repeated the reset process. I told myself if it happened a third time, I was RTBing to KBTL. In about 5-10 minutes, it popped a third time so I did a 180. On the roughly 45 minute flight back, the breaker never popped again. So, now I'm wondering if I made the right decision. Is this an issue that is just annoying or is it a safety of flight issue? How can I differentiate? What happens if I just keep re-setting the breaker? Is this caused by the alternator, voltage regulator, weak circuit breaker, something else? Has anyone else experienced this? Jack

My 2000 Ovation has the standby alternator installed, and I'm glad to have it in my all-electric plane. If the main 100 ampere alternator fails the backup 20 amp alternator can be switched on. If necesary the pilot may pull the battery circuit breaker and then the 20A alternator feeds only items on the "Emergency Buss" which include, in my plane: ESI2000 standby AI with airspeed and altitude Nav/com #1. GTX750 audio panel transponder & encoder TKS and pitot heat engine instrument cluster & glareshield lights but that's all. Originally the KCS-55 was also part of this emergency buss, says the POH supplement. The G500, GTX650, autopilot, shadin all go dark. (Even the XM music goes away, a real hardship) The idea is to save your battery charge (both of them) until approach when you can then run gear, flaps, landing lights & etc. That makes sense. Q: As the G500 only uses about 3 amps could it and it's related AHRS, magnetic sensor be connected to the emergency bus?

What brand alternator to buy? 2 years and 4 months ago, I replaced the alternator and regulator in my 1975 E model with a solid state regulator and a "Plane Power" alternator. Notice I said 2 years and 4 months. That is 4 months out of warranty and the noise (ac ripple) coming out of that thing is something terrible. Called Plane Power and they suggested a capacitor on the output. That didn't work. The whining noise in my headset made me shut down the electric bus after touchdown yesterday. Now the fact that I have to buy another alternator is just accepted. However, my question is what brand. I am not sure that I want to put another "Plane Power" alternator back on the bird. Any suggestions? Thanks, Jim

Hi folks. Just bought a 1974 M20F. Love it after only 10 hours of flight, but I have noticed something unusual with the battery charging system. Every once in a while the battery alert comes on in the jpi 700 and the auto pilot turns off due to insufficient charge. Concord battery is 2 years old. Checks out at 13.07 volts standing charge. Jpi 700 shows between 13.4 - 13.6 charging in flight, now that I’m watching it. I’m assuming my alternator is going out since I think I should see 14+ volts, but I don’t know whats normal. Thoughts?

Yesterday I tested the Standby Alternator in my Ovation 2 29-0363 (905 hours TTIS) all according to the published procedure, and it failed. To track down the fault the top cowl was removed, the prop rotated by hand, and we found the alternator was not rotating, so the problem seems to be the shear coupling. Have any other readers experienced the shear coupling failure, and at what TTIS? Was the alternator replaced or overhauled with the shear key replacement? It seems that the alternator is essential for TKS equipped Ovations, but not essential for non TKS. I'm not overly confident flying with the standby U/S because the G1000 equipped Ovation 2 needs plently of power, but then I accumulate some 1000 hrs on my first Ovation 1 (29-0156) in some of the most remote areas of Australia without the luxury of a standby.

Can someone help? Last weekend on my way home from Niagara Falls I lost charging. I turned off everything except the radio an transponder. I only lost 0.2 volts for a 45 min flight. It looks like the adjusting link broke and hit the alternator fan. The fan came apart and put the alternator way out on balance. The imbalanced alternator broke the alternator bracket. From the third picture, is there supposed to be that 1" spacer that looks like it offsets the alternator to align the pulleys. What is the correct bracket for mounting the alternator? Is this correct? The alternator is a ALY 8420 and has been repaired and tested.

Need to change mine and thinking of Planepower. Looking for model # and thoughts. I have LED landing light but the nav/strobes/etc are over powering the load a bit and I am having some other issues with existing so just want to replace it with a new one.

My K Model has two 80 amp alternators (two regulators as well). Amp loads are read from the digital Electronics International MVP-50. In flight, I'll get a warning a slight discharge (0.08 Amps) which is corrected when I take the #2 alternator off line. Both alternators test fine during run up when each is separately taken off line to test for charging ability. Any wisdom out these to pass along.

Used Plane Power AL12-P70 alternator for sale. Perfectly functional when pulled from my M20J when I did an engine swap to a factor reman. About 5 years in service. See photos. This will definitely fit any IO-360 Mooney. Check with Plane Power website for other effectivities. $250 + $20 UPS ground shipping anywhere domestic in original box. ($520 new at Spruce). Please reply to dhchang89@alum.mit.edu Thanks Dan N622DX

I have a 1980 M20J that had a Plane Power Alternator installed in it before I purchased the aircraft. It still has the same voltage regulator and my mechanics are having hell getting the voltage to stay between 13.0 and 14.5. I am getting very erratic swings on my ammeter (from -30 to +30) and it seems to be making my autopilot porpoise pretty bad. I had the Century 41 AP rebuilt and that did not resolve the issue. I am convinced that it is an issue between the voltage regulator and the alternator, so I purchased the Plane Power voltage regulator that is supposedly compatible. Apparently the M20J model is not listed on the approved airplanes for this regulator, so the plane will be grounded pending an FAA Field Approval. This is a crock of crap because the M20F IS a listed approved plane and that is pretty much the same aircraft, correct?? Has anyone had these issues or tried installing this voltage regulator on the J model? I would appreciate any feedback I can get from you pro's. Thanks, Michael Reitz 1980 M20J N3891H

I have had my Bravo for 3.5 years now, and in that time I have learned my share about the various aircraft systems. My latest learning experience resulted from the failure of my left alternator. I thought I would pass on the symptoms of the failure so others may also learn from what I observed. It all began about 20 flight hours ago. As I was cruising along at 15k', the low voltage indicator light started to flash at me. However, the volt meter still showed 28 volts and I had even loads on both alternators (both around 15%). A few minutes later the light went out. This happened a few other times over the next 20 hours of flight sometimes during ground ops, sometimes in climb out, and other times at cruise. Each time it would last between couple minutes up to about 15 minutes. On my last flight, a cross country from Florida back to Texas, the alternator warning light illuminated, the left alternator field circuit breaker popped, and the left alternator gauge indicated no load (as expected with the popped circuit breaker). I shut off the left alternator, reset the field breaker and turned the left alternator switch back on. Everything returned to normal (light off and alternator carrying about half the load). About 15 minutes later I glanced at the left alternator gauge and saw that it was now at 0 load. I had no other indications (light off and circuit breaker remained set). I shut off the left alternator field and continued the flight to my location on the right alternator. As part of the trouble shooting, my A&P and I swapped the alternator inputs into the voltage regulator to isolate the problem. Upon engine start and power up, the problem now moved to the "right" side of the voltage regulator. Having now isolated the problem to the left alternator itself and not the voltage regulator, we swapped out the alternator. All ops checks are good and the intermittent low voltage indication has also ceased. Nothing eye-popping here, but I thought I would share to help others recognize the symptoms. -Zam

Make me an offer. These came off our 1966 M20E. They were working fine and are guaranteed to work or your money back (less shipping). http://n2690w.blogspot.com/2015/02/alternatorregulator-off-of-m20e-working.html

These parts are from my 1984 M20J engine conversion. The alternator came on my new IO-360-A3B6 from Lycoming. It's brand new never used. Hartzell Engine Tech. ALZ-8521LS 70amp 12V $250.00 The starter is my old starter, never had a problem with it. I did replace the bendix a few years ago. Prestolite 12V MZ-4222 $100.00 Call Mark 925-200-3858 Thank you to everyone on this forum for all the help with my engine conversion. Mark me an offer.

So, I mentioned briefly in another post that my vacation flight to St. Simons Island became a vacation drive when the electrical system went south (without me!). The symptom was that I was showing now alternator output and the Low Voltage annunciator light and JPI voltage alarm were flashing, and no amount of resetting circuit breakers was helping. My A/P finally diagnosed that the alternator just wasn't generating the correct output, so we sent it back to PlanePower because it should have just still been covered by the 2-year warranty. They came back and said the cause was "oil contamination" and that it wasn't covered under warranty. Has anyone else ever experienced this? My engine has a few very minor slow oil seeps in a couple of places, but "it's no gusher" as my A/P says and in fact never shows any oil on the belly or anywhere else. I'm trying to think what could even be leaking near the alternator to cause this. Anyway, there wasn't much I could argue since they have the unit, and I can't prove or disprove their theory. They gave me a cutrate deal on a new one which will come with a new warranty (unless of course it gets oiled up again!) so I'll be back in the air this weekend. But dang...that was a new one for both me and my A/P.

Does anyone have any tips for removing the alternator on a 231 (-LB)? The SMM says: NOTE The main alternator is very difficult to remove. The lower engine firewall mount bolts may require loosening,the upper bolts may require removal and the engine pivoted around the lower attach points. I would really prefer not to have to do that.

Does anyone know what the P/N is of the alternator belt used in a vintage Mooney that was upgraded from a generator? I have a '66 E, the PO had an alternator upgrade done and my prop is being overhauled and I'd like to change the belt out while the prop is off. I think I heard that the alternator belt is just the same as the one the generator used, but I can't find it in the SMM or PM. Thanks, Harley