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Voltage fluctuation

jask

Well Known Member
I'M having a problem with voltage fluctuations. The needle movement is about 3 times per second for about 2 volts. I changed the regulator and the fluctuations ceased for about 4 hours flight time. Now they are back again. I am not the original owner of the aircraft. I read the first flight article and he had a regulator fail. He installed a VR-166 but had to do some rewiring to make it work.

I got a box or receipts with the aircraft and with it is a drawing of the electrical system that I think is installed. It lists a 1976 Honda Accord 50 Amp alternator and a 177-D510 regulator but that regulator failed on the first flight.

I will have to drop the cowl to see what alternator is actually installed.

Any idea why the voltmeter is showing fluctuations? What regulator should I be using?
 
I'M having a problem with voltage fluctuations. The needle movement is about 3 times per second for about 2 volts. I changed the regulator and the fluctuations ceased for about 4 hours flight time. Now they are back again. I am not the original owner of the aircraft. I read the first flight article and he had a regulator fail. He installed a VR-166 but had to do some rewiring to make it work.

I got a box or receipts with the aircraft and with it is a drawing of the electrical system that I think is installed. It lists a 1976 Honda Accord 50 Amp alternator and a 177-D510 regulator but that regulator failed on the first flight.

I will have to drop the cowl to see what alternator is actually installed.

Any idea why the voltmeter is showing fluctuations? What regulator should I be using?

I'll leave it to others to weigh in with specific regulator recommendations, but that will almost certainly morph into recommendations about alternators as well. I will say that I had a similar problem--voltage fluctuating relatively rapidly between roughly 13 and 15 volts. TTE was a little over 400h as I recall. On testing/examination, my alternator (PP 60 amp, internal regulator) turned up a bad rear bearing. There are several strings on this site about the relative merits of PP v B&C v auto store alternators, internal v external regulators, etc..., and I'd suggest you read through those.

What I can say is that PP stood behind their product in my case, and shipped a new alternator to me. My A/C was originally built with a single battery/single alternator electrical system. I'd intended to add a standby alternator system anyway, but given that I fly IFR as well as VFR, the voltage issue moved that mod to the top of my list. FWIW, I went with B&C for the spline-driven standby.

I don't disagree with the potential advantages of a second battery as well, but that's not currently in my plans. I do use a stratux (which supports a faux EFIS) and an iPad. Together, those provide a backup that is completely independent of the A/C electrical system. I have used them from time to time as part of my instrument proficiency efforts (in VMC with a safety pilot of course). I added a "gyro reset" item to my checklist, in case the stratux has been jostled since the last flight.
 
The first thing to check is for loose or corroded terminals and connections.
Other possibilities are a bad alternator on-off switch or bad alternator brushes or loose alternator belt.
 
Fluctuations

Why did replacing the regulator stop the fluctuations for a few hours flight time. Doesn’t make sense. I have another VR166. Should I try it?
 
Why did replacing the regulator stop the fluctuations for a few hours flight time
One of the wires that you touched might might be the one with a loose or corroded terminal.
 
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