High Voltage

[TheTurtle]

flying today for the first time at night.  Noticed my cigar lighter volt meter was bouncing around between 14.7 and 16.5.  My GEMIII  was staying solid at 15.4. (in angry red lettering)
  The ammeter wasnt spiking but I really dont know how reliable it is.  The needle does drop when I turn on pitot heat during runup so its registering something..

I turned off my landing lights which were on, but they are LED and dont draw much anyway.  Tried dimming the interior lights and panel lights with no change on the voltage.

Thats when I was was just going to flip off the alternator like in the cessnas I trained in only to find I have no alternator switch.  I guess as part of the conversion from generator a switch isnt required?  After landing I checked the CBs and there is one still labeled GEN.  I guess I could have tried flipping that one and maybe they wired the alt to it. 

I checked the log books and a yellow tagged ALY8420 alternator and VSF7203A voltage regulator were install in 1993 when the generator was removed.  New W&B was done but no mention of circuit breaker or any other wiring details.  I also thought most of you guys with Alternators have a low voltage light?  I dont have one of those either, although in this case it was high voltage.

Anyway..  Bad Alt or VR? 

[RLCarter]

Sounds like your voltage regulator went south. I just installed a conversion from Gen. to Alt. and it required a "Field" switch to be installed. 

[carusoam]

Voltage controllers have come a long way in the last 20 years.  Search on the word Zeftronics to find a supplier that makes some modern devices for our Mooneys.

My current plane was built in 1994.  It's alternator switch gets flipped on after engine start, followed by turning on the electronics...

My old 65C got a Zeftronics voltage controller to operate it's generator.  It was low cost and worked really well compared the original stone-aged device.

PP thoughts, not a mechanic.

Best regards,

-a-

[ArtVandelay]

Be aware that high voltage can kill your battery, check water level if a wet cell, and you want to fix this asap.

[Guest]

Some of those voltage regulators had an adjustment pot, if yours does you may want to see if you can lower the output voltage.  If it does not have an adjustment its time for a replacement, Zeftronics make good ones.

If it's been high for a while check your battery water level.

Clarence

[TheTurtle]

So some more digging.  The generator was swapped for an alternator some time before 1993 without a logbook entry.  In 1992 that alternator was replaced with a yellow tag.  In 1993 it was replaced again and this time there was a log entry saying there was no original logbook entry on the swap and a new W&B was done as well as installing a VR that had never been done originally.

I went out to the plane today and found the VR.  It looks like it does have an adjustment on it.

I fired up the engine and the voltage was bouncing around 13-14.7 but I saw it bounce up to 15.3 once.  I ran up the engine and it never hit 16 today.

While the engine was fired up I pulled the GEN CB and the volts went from 13/14 down to 12.9 and when I turned on all my switches the voltage started slowly going down.  So it seems like the GEN CB is connected to the Alternator.  Good to know for the future.

I havent checked the battery levels, Ill do that tomorrow.

I see the VR is connected to an old rusty box above it.  I cant quite read the numbers on it.  Anybody know what that thing is?

Aircraft spruce seems to have the correct replacement VR 07-00630  for $286.99.  Zeftronics.

[ArtVandelay]

Since the voltage is jumping around, I doubt an adjustment will fix it, might make it better, but if VR is working correctly, it should be very stable.

[Guest]

It's an over voltage relay, more common to Piper airframes.

Clarence

[TheTurtle]

Just now, M20Doc said:

It's an over voltage relay, more common to Piper airframes.

Clarence

Interesting.  Doesnt seem to be doing its job

[Guest]

Typically set to 16+ volts.

Clarence

[ArtVandelay]

Typically set to 16+ volts.

Clarence

So that's what's causing it to bounce around, the relay is closing, then opening, etc

[Andy95W]

6 hours ago, teejayevans said:

So that's what's causing it to bounce around, the relay is closing, then opening, etc

The over voltage relays I've seen open completely at 16+ volts and can only be reset by removing power (pulling the circuit breaker and resetting).

I still think the voltage regulator is starting to go, or at best, the voltage adjustment potentiometer is getting dirty.  Turning the adjustment back and forth a few times and putting it back where it was would be my first idea, then test run to check the voltage output.

[TheTurtle]

Just now, N1395W said:

The over voltage relays I've seen open completely at 16+ volts and can only be reset by removing power (pulling the circuit breaker and resetting).

I still think the voltage regulator is starting to go, or at best, the voltage adjustment potentiometer is getting dirty.  Turning the adjustment back and forth a few times and putting it back where it was would be my first idea, then test run to check the voltage output.

the connections look a little corroded as well.  Im going to clean them all off and move the Pot back and forth a few times and take it for a test flight before dropping $280 on a new VR. 

[mike20papa]

I see lots of possibilities for probable corrosion related electrical connection failures.  My IA thinks the most overlooked system of any light AC built since 1990's is the wiring.  Thinks it's the FAA's most overlooked area to issue those hateful, sweeping AD's.  I completely rewired my '59 A model, and while it was no simple task, it sure was worth the effort.

Edited August 26, 2016 by mike20papa