Voltage output on Mooney Acclaim

[Showmethemooney]

I have an '07 Acclaim that is exhibiting output voltages that vary 1.5 volts - from about 28.5 to nearly 30 volts while in flight. Often it appears stable but sometimes in flight, I see the voltage fluctuating the full 1.5 volt range. I am thinking the voltage should not vary more than a tenth or two tenths of a volt.

 

I just had the brushes replaced in the alternator; we thought that might have been the problem but it did not appear to solve the fluctuating voltages.

 

I do have noticeable alternator whine, with some pulsating that varies with engine RPM, not sure if it is related.

 

I have a Zeftronics voltage regulator, thinking about replacing it.

 

Any thoughts are appreciated.

[orionflt]

Have you checked your grounds?

[DAVIDWH]

In my case it was the Zeftronic.

[Showmethemooney]

Have you checked your grounds?

I am not sure I can identify all the ground points, no schematic. I did check all the master switch connections, worked them a bit by hand just in case one had a poor contact, no difference noted. 

[Showmethemooney]

In my case it was the Zeftronic.

Thanks David. That's interesting to note. Were your symptoms the same as mine - voltage fluctuations? What year is your Ovation? Possibly a batch of voltage regulators were prone to this. My Zeftronics voltage regulator part number is A25EAM and the serial number of is T3K019. I hate to bother you to look at your log book but I would be interested to know your old regulator's serial number.

[DAVIDWH]

Doug,

 

Sorry, no serial #'s available as aircraft recently sold. However symptoms much the same in the air as well as taxi.

 

They make a great regulator, but as with everything, tolerances will change over time. Hate to be just a parts changer, but if it is not

 

regulating properly, it is a relatively cheap fix. 

[Showmethemooney]

I finally solved my charging system problem... thought I would share it in case someone else ever experiences the same problem.

 

To recap, it began at first with an occasional overvoltage reading (30+ volts caused the yellow voltage alert on the G1000.) At annual, my Mooney service center adjusted the voltage regulator (actually, it is called the alternator control unit), but soon I was seeing the overvoltage again. I noticed too that the voltages were fluctuating quite a bit - about 1.5 volts.

 

I checked impedances on the charging system circuit breakers and found the alternator voltage sense breaker to have anywhere between 3 and 90 ohms depending on when I took the measurement. I replaced that breaker and problem solved. My voltages were steady and actually fell to 26.3 volts, causing me to need to adjust the alternator control unit (voltage regulator) up about 2 volts due to the fact that we had been adjusting it down previously. I would say the ACU was seeing a varying voltage dropped by the high impedance of the breaker causing it to increase the field current to the alternator.

 

 And my headset whine was much reduced! 

 

Curious, I split the old breaker and saw that it was burned inside.

 

- The world is right again -