Bus voltage lower in cruise after annual

[Thedude]

I have a 79 J model and I got my plane back from annual at the beginning of this month. Nothing with the electrical system was touched, but I've noticed in cruise that my bus voltage is around 13.2 rather than 13.8, which is what I used to see while in cruise.

Everything seems to be working fine, but I'm not sure why the bus voltage is so different and if I need to be concerned about something. The battery is a Concorde that I replaced about a 10 months ago at this point.

[Flyler]

On my 79 J we recently found the field wire to be broken right where it connects to the alternator.  Possible it is breaking on yours and giving a warning sign. I just had my head in/under the instrument panel and on my plane the Voltage Regulator is under the glareshield on the right side, if that helps.

[Ragsf15e]

1 minute ago, Thedude said:

I have a 79 J model and I got my plane back from annual at the beginning of this month. Nothing with the electrical system was touched, but I've noticed in cruise that my bus voltage is around 13.2 rather than 13.8, which is what I used to see while in cruise.

Everything seems to be working fine, but I'm not sure why the bus voltage is so different and if I need to be concerned about something. The battery is a Concorde that I replaced about a 10 months ago at this point.

It should be higher.  Something like 13.8-14, but it’s in the maintenance manual or on concorde’s website.  You’ll get a lot of thoughts on this and you’ll get told it’s the Voltage reg or the alternator or the battery or don’t worry about it.  Speaking of which, what type of vr do you have?

 The best thing is probably to troubleshoot this yourself before just handing it to a mechanic.  There is a troubleshooting guide on the Zeftronics website or planepower has one on their alternator website.

I had a similar problem and ended up having to measure my voltage coming off the alternator with a digital voltmeter.  It was 14 even though the bus was 13.2.  Hmm, it’s probably not the vr or the alternator .  Then follow it back and see what connection be leaking voltage.  Fixed.

Unfortunately, this was after I did what i told you not to do and we had replaced several parts for a good bit of $$ and it was still broken.  

[gabez]

have you tried to shed some load to see if the voltage goes up? or you can add some load like USB charger etc and see if the load goes down. 

 

[Thedude]

I believe this is the voltage regulator, (fortunately have photos from my last oil change) which is a plane power, I need to find details about the alternator, but I believe it's also a plane power.

 

Looking back at my old photos, I guess even when I got the plane a year ago it was reading 13.2. I'm not sure why more recently it was reading 13.8 just before the annual, maybe something finicky with the wiring. At startup and through runup right now the voltage reads above 13.8, it's just in cruise it seems to be lower than what I used to see, but the same as what I saw when I first bought it a year ago... I guess I should have been paying more attention.

 

Changing load in flight doesn't seem to affect the reading.

[Ragsf15e]

54 minutes ago, Thedude said:

I believe this is the voltage regulator, (fortunately have photos from my last oil change) which is a plane power, I need to find details about the alternator, but I believe it's also a plane power.

 

Looking back at my old photos, I guess even when I got the plane a year ago it was reading 13.2. I'm not sure why more recently it was reading 13.8 just before the annual, maybe something finicky with the wiring. At startup and through runup right now the voltage reads above 13.8, it's just in cruise it seems to be lower than what I used to see, but the same as what I saw when I first bought it a year ago... I guess I should have been paying more attention.

 

Changing load in flight doesn't seem to affect the reading.

That one might be adjustable, but id go through the plane power troubleshooting first.

[Thedude]

Looks like I have a plane power 10-1050-1 alternator and a plane power r1224 VR that were both installed in 2021. I need to do some reading on what I can configure.

[Ragsf15e]

8 minutes ago, Thedude said:

Looks like I have a plane power 10-1050-1 alternator and a plane power r1224 VR that were both installed in 2021. I need to do some reading on what I can configure.

You’ll still want to troubleshoot it, even if it’s adjustable.  Just in case you have a bad connection somewhere, you might be able to cover it up by turning up the vr, but just masking the problem.  I want to say there’s a troubleshooting guide on the plane power website.