Low Voltage problems

[N8632Y]

In my PA30C i sporadically run into a low voltage situation, here today, gone tomorrow, then back.
My JPI will show 11.2V and the Low Voltage yellow light on the dash lights up.
I shed some load, no avail, no breakers have popped, so i'll switch to the Aux Volt Reg, all goes back to normal
charging, 13.8 in my bird.
After a few minutes, the voltage quickly will drop to 11.2 again, i switch back to main volt reg, and it goes back to 13.8
This may repeat itself, or not...
I've even shut the master off for couple minutes, then all back online, fine, but this may repeat itself, and next flight fine....

Any thoughts? thanks for any imput, is it time to switch to the plane power system, and would you do alternators and regulators?
steve

[Edward Pencosky]

Isn't your battery suppose to be at least 12 volts? and anything lower is showing a tired battery?I am thinking that maybe your charging system charges the battery a bit than cuts off and than the battery slowly looses voltage.Maybe it is time for a new battery.Can someone tell us what volt reading we should get on a good battery and if 11.4 is acceptable.

[DAVEG24]

deleted

[md11flyer]

Steve:
I also converted my Pa-30 over to the plane power alternators. They are a thing of beauty, install and forget.
The kit includes all that you need including the solid state voltage regulators and brackets to install the alternators.
The voltage regulators have a small adjustment pot that allows you to fine tune the voltage to exactly 14 volts. (at 15 degrees celcius).
The 2 voltage regulators have the alternators share the load, all electronically, no points to wear out or stick.

I am not sure, don't remember reading it in the manual, but I believe the voltage regulators also automatically adjust the voltage output with regard to
OAT.
These are 70 amp Alternators, so if you want to use the full capacity of the alternators you need to upgrade the cable from the alternator
to the fuse box and exchange the 50 amp breaker for a 70 amp breaker.
I had a discussion about if this was necessary and the concensus was that it wasn't necessary as the full ships load was well below the 50 amps.
Only time were you might need the 70 amps if you have weather radar, hot windshield deice plate, coffee maker etc.

Gary

[Kristin Winter]

You have an intermittent overvoltage situation, I am betting. If you watch the voltage after you reset, you might see it spike to around 16 voltage before the overvoltage relay kicks the alternators off line.

When I happened to me, I threw in the towel after a day of troubleshooting and installed the Plane Power system. As a bonus, you gain a bunch of useful load. If you have a C model, you can get rid of a massive amount of wiring and other crap. Here is a picture of what I pulled out.

I did things just a bit differently as I obtained a split master switch, with each half handling the field circuit to one side, instead of using switch/breakers.

The installation is much cleaner that the system in my C model and much more reliable.

[N8632Y]

thanks for all the posts,
nice pic too...
seems like forget the problems, just replace w/ newer technology....
wires, and more wires...sigh..same w/ gear, and everything else..
steve

[Kristin Winter]

You will be amazed at how little new wire replaces all that crap.

The instructions are not great because they really assume that you are replacing generators with their system. However, a bit of common sense and a bit of advise from someone who had done it before, made it all work. If you decided to go that route, send me your email address and I will send you a few pics that might help.

[N8632Y]

Kristin,
I would like to update to that system, pictures would be nice, my AnP is pretty good, I'm sure he'll be ok, but pics would help.
My email:
StevenMDavis@comcast.net
thank you!

[Ron Davis]

Had the same problem and went over everything for years before I finally figured out what was going on. Solution started to become clear when my JPI was updated to a new factory replacement. For some reason I actually read their (JPIs) instructions before i reinstalled. The big JPI (warning) says do not use bulkhead or airframe grounding use only engine ground. THAT WAS the REVELATION. Surely this couldn't be the problem even though is resonable there could be a slight difference. So, I decided to follow the instructions. In my case Low Voltage had been a reported problem which even predated the ownership of my airplane. My pre buy mechanics was unable to identify the error which was a squak I had years ago when I bought the plane. I was overconfident and had not let this factor in to the purchase. My final proof of a solution occured when I placed ground straps between regualtor bulkhead ground and engine frame ground. This became the common point ground to the JPI. The problem went away.

This has been a long standing issue on my airplane which had nothing to do with the alternator and regulator. Using adjustable regulators without further checking because the JPI is saying low is probably not a good idea. You could be raising the voltage above nominal to make up for a poor ground. As your alternator load increases the JPI would report the total it sees after subtracting of the Voltage drop across the poor ground. More stuff turned on the lower the Voltage reported. Too bad as this not the actual Voltage going to the radios. Like so many others, I had checked my regulators on the bench more than once. All of them tested within 1/10 of a Volt every time and very close to 13.8 V. Yes, I bought two spares out of frustration. Moral of the Story; The JPI is very sensitive and must have a low impedance connection to the engine ground for instrumentation to be correct. So too must the regulator have engine ground (same as the alternator it is regulating) to keep altenator putting out the proper Voltage to the airframe where all the power is drawn. Remember the Alternator is engine mounted and just like JPI says: Engine ground and frame grounding arn't the same unless you have a low impedance (good ground strap) tying them together. Strap must be substantial as to avoid any voltage drop even under high current loads. Now my Voltage indicated on the JPI is right where it should be and the Mystery is solved. Ron

[N3322G]

Ron,

Very interesting. Thanks for sharing. I'll have this looked at next annual.

[Jay]

Thanks Ron, that's good information.

Jay

[N8632Y]

Ron,
I'm not sure i'm following you.
Are you saying that your low voltage issue was being reported as "low voltage" by your JPI. But due to the grounding technique, was not entirely accurate?
I have 3 "low voltage" indicators.
the jpi, the low voltage light on top of panel, and my sam GPSS icarus.
I should have gone to school to be an electrician!
steve

[Ron Davis]

Yes Steve, My JPI was gounded at the airframe radio panel. This is unacceptable and just like JPI says will produce bad results. It shows low Voltage because the place where the powere comes from has a different ground potential. Notice how the Voltage indicated drops as time goes by. As current continues to flow through the airframe the Voltage drop accross the airframe ground increases and the JPI shows that as a lower Voltage. If on the other hand like a modern auto the regulator is placed at engine ground potential by being located in the alternator the current flow in the airframe can not affect the Voltage sense of the regulator. Same deal as the JPI. Can't put the regulator in the alternator on our Comanches but regulator ground should be isolated like the JPI ground so that they are connected directly to engine ground. See JPI insturctions.



I add one more comment to help explain why a airplane with out a good solid connection can have electrical problems besides just reading low Voltage. The instrument of measurement like the JPI should have a direct ground connection to the engine frame since that is where the power source is located and should not be allowed to come in contact with other grounds along the way. To read the power bus with respect to airframe ground is a different story and comparing the two should provide you with how effective your airframe grounds really are. The poorer your engine ground is connected to the airframe the lower the Voltage will be reported by a JPI improperly connected to airframe ground. Ron