Generator Voltages

[DaV8or]

My plane has the original style generator and voltage regulator in it. My JPI has been telling me the voltage is between 11.9 and 12.1 a good bit of the time and it often flashes "BAT" at me. However, sometimes it reads 12.6 and all is fine. Turning off equipment seems to make no difference and the factory amp meter reads near zero all the time. My guess is the regulator is screwy, but I intend to check all the cable connections and get an actual voltage reading at the battery. The logs show that previous owners have fooled with the regulator before. A few questions;

What voltages do you get?

Where does the JPI measure the voltage, battery, regulator, master...??

Is the alternator conversion a good idea?

[Lood]

My JPI's alarm usually only goes off when I reduce rpm to below 1000rpm to do the mag dead cut check. I'm not sure where the voltage sits when I'm on the ground taxiing around at 1000-1200rpm, but in cruise flight, the JPI normally shows the battery voltage to be around 14,8 volts. I don't know where exactly it's measured though.

[MooneyMitch]

Hi Dave.

With my experience, you should be reading approx. 14.2 Volts [above 1200 RPM or so] from your generator electrical system.  Either your generator and/or regulator is not doing its job, or you have a poor and/or corroded connection someplace.  You can measure the output voltage on your cockpit bus bar, using a DC voltmeter.  Place one lead on the live bus, the other to the airframe ground, run the RPM's beyond 1200 and see 14.2 volts on your meter. 

You can find [Google] specific testing/output information for each unit [generator and regulator].  Do exercise caution and use long volt/ohm meter test leads while sitting inside your airplane as you perform the tests while your engine is running. 

I have had excellent success without converting to an alternator.  With that said, and you are doing tons of night flying with all accessories/avionics/landing lights powered on, it is possible to weigh down the 50 amp electrical system as you pull the power back for approach to landing speed.

I hope this information helps.

[scottfromiowa]

My E.I after market gauge reads 13.7 to 14.1.  Mine also goes to discharge (light comes on) when I reduce power for landing (pull power) in slow 1200 rpm taxi...

I replaced my voltage regulator with zeltronics unit and I also replaced my generator and belt (two separate incidents of power loss).  I put in an HID landing light and my illumination went from nil taxing at night to WHOA!  HID draws a lot less amps...

My plane shows little draw with landing light, transponder, two radios, intercom, panel mount gps running.  I do NOT plan to replace my generator, but do recommend a new/updated voltage regulator if yours is OEM.  They are NOT expensive.  After install they do need adjustment so as to be NOT over or undercharging your system.

[MooneyMitch]

In my experience, with regards to the Zeftronics regulator I installed, there was no adjustment required.  Output remains constant at 14.2 volts DC above 1200 RPM. 

[rdv]

I see about 14 and a bit in cruise.

[scottfromiowa]

HMMMmmm, just going by what my A&P said following the installation.  If it is a 14 volt system why would you want to charge at a level above 14.0 volts?  Curious as I am no expert on the electronics of my '66 E.

[MooneyMitch]

Quote: scottfromiowa

HMMMmmm, just going by what my A&P said following the installation.  If it is a 14 volt system why would you want to charge at a level above 14.0 volts?  Curious as I am no expert on the electronics of my '66 E.

[Jerry 5TJ]

Quote: Mitch

I do believe that in your E model, the system is actually 12 volts DC.  The Zeftronics folks feel that a charging voltage of around 13.8 - 14.2 volts is optimum for keeping your battery charged, but not overcharging.

[scottfromiowa]

Thanks Mitch.  I'm good.  Mine is right in that "sweet spot" you describe.  I will follow up as I was initally reading lower (right after install of EI volt/amp meter) than current level and mechanic said he adjusted the unit...Regardless I have had NO issues in over 18 months since replacement of generator/belt (my generator was OEM and logs showed no previous failure) and EI gauge gives nice piece of mind...Now I just need to get my fuel flow installed.  I had some breakers moved and the wire to the panel GPS run, so spot is cleared.  Will probably wait until annual.

[DaV8or]

Thanks for the replys. It is as I suspected. The voltages you guys are seeing is what I would expect for any car, motorcycle or boat I would be working on, but this airplane business is all new to me. Just thought I'd check. When I get back from Oshkosh I'll tackle this problem. First I want to check the connections myself. I know where the generator and battery are and I believe the voltage regulator is on the firewall on the co-pilot's side (I could be wrong), but I don't know where the avionics buss is located. I suppose some of you may know? If all looks well with the connections, then off to Top Gun again I guess.

[MooneyMitch]

Quote: DaV8or

Thanks for the replys. It is as I suspected. The voltages you guys are seeing is what I would expect for any car, motorcycle or boat I would be working on, but this airplane business is all new to me. Just thought I'd check. When I get back from Oshkosh I'll tackle this problem. First I want to check the connections myself. I know where the generator and battery are and I believe the voltage regulator is on the firewall on the co-pilot's side (I could be wrong), but I don't know where the avionics buss is located. I suppose some of you may know? If all looks well with the connections, then off to Top Gun again I guess.

[DaV8or]

Quote: Mitch

I can't imagine that Top Gun would miss this issue for you.  This might be something that has just happened with the generator or regulator.