Electrical? Issue

H. Paul Shuch is a Light Sport Repairman with Maintenance ratings for airplanes, gliders, weight shift control, and powered parachutes, as well as an independent Rotax Maintenance Technician at the Heavy Maintenance level. He holds a PhD in Air Transportation Engineering from the University of California, and serves as Director of Maintenance for AvSport of Lock Haven.

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rcpilot
Posts: 356
Joined: Fri Jul 03, 2015 4:32 pm
Location: Mastic, NY

Electrical? Issue

Post by rcpilot »

So my plane has not been playing nice. I have a Rotax 912 ULS. A couple of weeks ago I went to fly and when I flipped on the radio, no sound. I checked and the headset was jacked in. When I went to unplug it as soon as it was half plugged in I had sound. Shove it in all the way, no sound. Called the Unicom and verified they could hear me. Taxied over to pick up a passenger. They plugged in their headset and nothing. I couldn't hear them and they couldn't hear me. Went flying and no other apparent issues. Went flying the following week and I'm cruising along at 4800 RPM and I get a low volt warning light. The volt meter drops back to about 12 volts. It lasts a few minutes then the light goes out and the voltage goes back up. A few minutes later and this happens again. When I search out the symptoms I find posts that seem to indicate it's either a loose wire, corrosion on the connector to the voltage regulator or a bad voltage regulator. I have a look, I have a Ducati voltage regulator(apparently there is a newer model). All the wires seem tight. I unplug the wiring connector and verify that there is no corrosion on the connectors. I clean off the contacts with some cleaner and hook things back up. I try and test it out again today. Same issue with the radio my no low volt light and the volt meter is looking good. As I'm taxing to the run up area, the low volt light comes on and I hear a "buzzing" sound from behind the instrument panel. The low volt light is flickering seemingly in sync with the buzzing. My radio sound is cutting out as well. I taxi out of the way and see what's going on. Well the light goes out, the volts go back to normal and the radio is working as it had. I taxi back to the run up area, do my run up and take off. Just about as I do the voltage drops below 12. I was staying in the pattern so I bring it around and land. As I taxi back to my parking spot the voltage is below 12 but no low voltage light. I get back to my spot and shut down. I have a look under the hood and nothing has changed. I'm thinking at this point I probably need a new voltage regulator. There is one other device I don't know what it is but I'm wondering if the noise I heard was coming from it. In any case I start up again and now the voltage is normal, no low volt light and no buzzing. I run it for a while and even load up the system(lights, radio, transponder, standby pump all on). Voltage stays above 12 at 4000 RPM. For shits and giggles I try the passenger headset and low and behold it's working now. I check mine and I can fully seat the jack and things are find. I'm probably going to try some more flying in the pattern to see what's going on with the voltage but anyone have any idea what could be causing this? Should I just replace the voltage regulator? What the other device? Very confused.
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3Dreaming
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Location: noble, IL USA

Re: Electrical? Issue

Post by 3Dreaming »

The thing your arrow is pointing to is the starter relay. Before I would replace the voltage regulator I would check all of the ground connections. Maker sure they are clean and tight, especially where the avionics are grounded.
Wm.Ince
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Re: Electrical? Issue

Post by Wm.Ince »

That positive (red wire) lead is badly corroded.
Bill Ince
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rcpilot
Posts: 356
Joined: Fri Jul 03, 2015 4:32 pm
Location: Mastic, NY

Re: Electrical? Issue

Post by rcpilot »

My mechanic and I were going to do some other work so I guess while we're at it I'll disconnect the wires and clean the connections. Some of that's going to be a 2 man job anyway.
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FastEddieB
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Re: Electrical? Issue

Post by FastEddieB »

A lot of Cirrus owners swear by Stabilant-22 to apply to critical electrical connection.

Not cheap, but a little goes a long ways, a drop at a time. Available on Amazon.

Then followed by a corrosion-inhibitor sprayed on, something like Corrosion-X.
Fast Eddie B.
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CFI, CFII, CFIME
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rcpilot
Posts: 356
Joined: Fri Jul 03, 2015 4:32 pm
Location: Mastic, NY

Re: Electrical? Issue

Post by rcpilot »

So more testing today. I'm thinking it's not the connections(not that I won't check them)because when I first start everything works fine. Voltage 13+ at about 2200 RPM. After about 5 minutes I hear a buzzing sound from the right side of the instrument panel, I get the low volts light and my voltage drops to 12 or just under. The only things on that side are the engine gauges, oil pressure, temp water temp, fuel pressure, fuel gauges and the volt meter. After a few minutes the buzzing stops but the voltage continues to be around 12. Guess we'll pull the right side panel and see if we can figure out where the buzzing is coming from. Does that fact that the problem starts when the engine warms up point to the voltage regulator?
rcpilot
Posts: 356
Joined: Fri Jul 03, 2015 4:32 pm
Location: Mastic, NY

Re: Electrical? Issue

Post by rcpilot »

So we swapped out the voltage regulator yesterday and added the "missing" capacitor. The thing is huge. I was only able to do a limited test. One trip in the pattern because it was a bit windy(22 kt gusts). No low volt light and voltage looked good even when I was taxiing with everything turned on. When weather cooperates I'll do a longer test flight but so far looking good.
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ShawnM
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Re: Electrical? Issue

Post by ShawnM »

My 2007 SportCruiser didn't come with the smoothing cap either. Made a huge difference in my instruments as well. The readings were a little jumpy without the cap and they are rock solid with the cap.

I upgraded my voltage regulator a few years ago to the Silent-Hektik and it requires a 33,000 mfd cap rated at 40 volts. It steps the voltage output to 14.2 volts after about 30 minutes. It's designed this way for the lithium type batteries.

Glad you seemed to get the issue sorted out, now please do us all a favor and clean your engine compartment. :mrgreen:
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