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Touring Motor Gliders Association (TMGA)

voltage regulator fail


Art Daun

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Recently had a sudden drop of dynon indicated voltage to 11.3 volts. This was the indication with either battery selected or both selected. It was accompanied with a failure of the low voltage light to come on with the engine stopped. My mechanic could not come up with a method of actually checking the voltage regulator but on the advice of Lockwood aviation we replaced the voltage regulator with a new one ordered from Lockwood. This change out fixed both problems. The indicated voltage on the dynon with the engine running is 13.5 volts. According to Lockwood a gradual fall of this voltage is indicative of a failing voltage regulator—it doeanʻt have to happen all at once. In retrospect, I thought that an indicated voltage in the 12.3-12.5 range was adequate and it actually was telling me that a failure was occuring.

The voltage regulator is located on the engine side of the firewall just opposite the dynon display. It was fairly easy to access by moving the dynon out of the way on the cockpit side and removing the left air filter on the engine side. Definitely a two person job.

598CBE57-1DDB-434F-9705-DB18AB3EDD1B.jpeg

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I am sorry to disappoint you but after having experienced the same identical symptom twice with my 912 ULS each time I was guided by my importers A&P and Joe, the SM of Lockwood to suspect the 6 wire gang black plug you see in the photo at the bottom of the regulator.  I removed the plug and lubricated and reinstalled and the voltage charging started back up.  After this happened the second time I was guided by my local A&P to remove the female spades from that black housing, put new females ends on the wires and reattach using dielectric grease and so far no problem.  That black plug combined with weak female spade receivers & gravity/vibration is a weak link in the electrical system of these engines.  Be prepared for it to happen again...

I will say it is disconcerting to experience low voltage/no charging when you are flying on labor day and have 2 hours to go.....But R&I of the plug worked again....Best wishes Art...Steve Chase with my Bristell at almost 500 hrs.....

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We did remove, inspect (saw no abnormalities) and reinsert the plug but it had no effect on the problem. The new voltage regulator came with a new plug and spades neither of which was used in the change out. If the problem recurrs I will follow your advice. Not sure if we had the same problem because of my gradual falling voltage. Thanks for the input. Art

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Mine was a sudden drop and I thought your first sentence “Recently had a sudden drop of dynon indicated voltage to 11.3 volts. This was the indication with either battery selected or both selected.” Meant we had the same kind of problem? Glad you didn’t waste your money Art. 

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FWIW, I have a 1998 Ducati ST2 motorcycle. The regulator on mine went out twice in spite of redoing the wiring. The fix was to replace the antique diode-bridge regulator/rectifier with one used by Yamaha. It's a FH020AA mosfet kit: http://roadstercycle.com/

Of course, the FAA would forbid such a thing in the name of safety. The key to making the old ones last was cooling. Being a primitive, inefficient design, they get hot (even hotter when one of the diodes short to ground, which they inevitably do).

 

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  • 2 years later...

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