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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.

Charging voltage started reading high (up to 15.2V - my understand is that it should be in the 13.4 to 14.2V ) any idea why would that happen ? Voltage regulator failing ? Alternator ? i have an OECO voltage regulator. Not sure they can be adjusted. What replacement options do I have if it came to that ? 77 M20J

Hey... been having a problem where the alt field breaker keeps popping in flight (M20R Ovation II). I had a first mechanic look at it... he sent out the voltage regulator... mooney said it was fine. Mechanic checked all the connectors, fuse, and batteries... all looked fine.... Replaced the diode... did not work... rebuilt the alternator... appeared to work for about 4 hours... then it popped again in flight. Took it to a new mechanic.... he found chafing in the field coil wires. However, fixing that did not seem to fix things. The new mechanic tested everything again... including the alternator. He narrowed it down to the voltage regulator. Sent it to mooney.... mooney checked it and said it was fine. The mechanic is pretty sure it is the voltage regulator. Has anybody had any odd failure modes with the voltage regulator that mooney did not find at first glance? This is getting very expensive and my plane has been down for months... please help!

I have a 77 201 S/N 48. Where is the voltage regulator located? Not on the firewall. Battery isn't charging and voltage is low at idle. Going to clean / check connections before I start throwing parts at it.

My voltage regulator drives the voltage to 13.5, which is low by about a 0.5V i never thought about it since my experience with voltage regulators has been with the multistage type and typically the 3rd stage is 13.5, so now i found out they are simple 1 stage. my VR was installed back in 2003 by PO and the mechanic recorded in the log that it puts out 13.5v signs off the repair as all is good, fast forward to now, i called the tech at Zeftronics and they're going to send me some trouble shooting doc, but being both cheap and lazy, I was wondering if anyone else has seen this problem, especially for those with problematic Gills? This VR doesn't have any external adjustment.

Cant find a voltage regulator for my m20k 252 with single alternator It had a electro delta VR802 part number on the current regulator, Lasar gave me two new part numbers of 800270-501 Or 940170-501 I have tried maxwell, dugosh zefttronics. No one has part and says it would be weeks and cost vary from 800 up. Crazy. Anyone have one for sale? Thanks

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

Hello fellows, I'm looking for m20j Instrument Cluster, Oil and Fuel Transducer and Voltage Regulator. The P/N are bellow: Instrument Cluster - P/N 640281-523 Transducer Amplifier Fuel - P/N 950D0311-001 Transducer Amplifier Oil Pressure - P/N 950D0311-003 Voltage Regulator (28V) - Electrodelta VR802 (or any alternate, Mooney informed me that actual alternate P/N is 940170-501) Regards Tércio

i believe my 77J still has its factory installed OECO voltage regulator. the POH is very vague: it says Oeco and refers to a drawing number but there is no part number. i wonder if anyone had experience replacing one of those with a more compact solid state type of device (zeftronics). zeftronics has a few options but i am not sure about what i currently have and what kit would be needed to convert. it is a pain to get to and i could not take a picture to clearly identify. ( i wish the regulator was installed on the firewall on the engine side.