K model voltage regulator

[DonMuncy]

Lee,

You continue to amaze me. I poked around some more, finding that my JPI was on the aux bus CB. I cycled it a few times, and now the JPI reads normally.

Thanks a million to you and all the others who volunteered info.

Lee, do you plan on making the MAPA convention in Kerrville next month. If so, I'll buy you a beer, etc.

[laytonl]

The overall knowledge base on Mooneyspace is amazing. I won't be in Kerrville, but my hanger neighbor, Bob Belville, might be there. You can buy him a beer. Take care, Lee

[DonMuncy]

Thanks. If I catch him, I will.

[DonMuncy]

To continue this thread, my system has reverted to its old habits. The JPI is reading 12.9 volts. I suspect the circuit breaker is just bad. But first I think I need to clean its contacts. The CB is a ceramic looking affair that appears to defy squirting anything inside. It would probably be best to take it out and see what I can do with it. There appears to be virtually no room to get to its external connectors with it in place. Is it perhaps more feasible to pull the CB panel out the front to gain access. Has anyone done this chore.

[kortopates]

It's pretty involved to pull back the circuit breaker sub-panel. In addition to the few screws on the front there are two screws coming inside from outside of the fuselage and an Adel clamp underneath towards the rear of the tray - plus a plastic insulator that is pop-rivetted onto the right hand side. Then you'll be surprised to see it may only pull back about 4" or so and you'll need to remove adjacent breakers to get access to a middle breaker. The hard part will be aligning the fuselage screws with holes in the sub-panel tray to get them back in - use an awl to find the first one. If you pursue this, be sure to follow the maintenance manual steps. Sent from my iPhone using Tapatalk

[DonMuncy]

I looked at the manual and did not see a procedure for it. Did I just miss it. Is there any way to change the aux bus breaker without pulling that panel out.

[kortopates]

See 39-10-03 along with fig 39-2 and there is no other way.

Sent from my iPhone using Tapatalk

[DonMuncy]

How foolish of me. I was looking in the electrical section. Thanks for the help.

[DrBill]

I would test it with a Volt meter before changing anything.  I suspect a bad connection somewhere..

BILL

[DonMuncy]

Bill, I previously checked at the alternator and had good voltage there. I then cycled the aux bus CB(which controls the JPI). This caused the JPI voltage to increase considerably. However, it has now dropped to about 12.8 again. I concluded that if cycling the CB changed it, it is almost certainly the culprit.

[DonMuncy]

I'm still working on my low voltage problem. The voltage showing on the JPI is now 12.8 again. Tomorrow I plan on going out and checking the alternator output again.

My question is, if the alternator to ground voltage matches that of the JPI, at 12.8, does this mean it can be either be the VR (limiting the alternator too low), or a defect in the alternator itself.

Naturally, if the alternator voltage is up at or near normal, it could be bad connections.

If the alternator is only showing 12.8, I plan on checking the diodes for proper resistance (in each direction). If they seem OK, it would appear the alternator is going to have to come off.

Any ideas?

Lee?

[tony]

Before you start removing parts, just might just need to clean up the grounds.  In my aircraft, I found that the shelf, where the battery was grounded to, was painted and not making a good ground to the airframe.  The shelf had to be taken out and cleaned up. 

 

Just for trouble shooting purposes run a wire from where the alternator is grounded to where the JPI is grounded.  See if it makes a difference.

[N601RX]

Which JPI do you have?  If its the 900 or 930 then it is supposed to have separate wire that runs back to the master relay beside the battery.  If this is the case it will read between .4 to .8 volts lower than what it would if it is connected to the avionics bus.  That is one of the 1st things I noticed when I swapped my 830 out for a 900. The 830 was connected to the avionics bus. I also found out that I had been undercharging my battery due to this. I was originally concerned about this and thought something was wrong, but most all of my wiring and all CB and bussbars are only about 2 years old.  After looking into it some more I found the Voltage Drop across  the components was more than I had suspected. The picture below shows the voltage drop across some of the more commonly used switches and CB at rated load, which they normally don't ever see.  Throw in the wire and current shunts and it will add up pretty quickly.

V.bmp

[laytonl]

Don,

I didn't go back and re-read this entire thread. Are you sure you have a low voltage problem? Have you verified the bus voltage other than with the JPI, say checking voltage at the power outlet (I.e. cigarette lighter) with a voltmeter? If you have verified the voltage is low, then let me know two things,

1. With the engine off and master on, what is the voltage at the battery and at the F terminal of the alternator, and

2. What is the resistance of the F terminal to ground?

The difference in the voltage at the battery and at the F terminal should be less than 1.5 volts. The alternator field resistance should be between 4-6 ohms or so.

Unless the voltage is changing with load, I doubt it is a alternator diode.

If the problem is just a low voltage reading at the JPI then I suspect it is the CB to the JPI. You could confirm this by temporarily wiring the JPI straight to the avionics bus with an inline fuse and see if the voltage reads normal.

Let us know what you find.

Lee

[DonMuncy]

To recap;

My problem is somewhat variable. It started with my JPI reading 12.8 volts (confirmed with another VOM).

Cycling the circuit breaker to the JPI gave an initial boost up to 13.4v, but later dropped to 12.8 again. I concluded the breaker was bad and replaced it. Much cost, much work, no help. Still variable from 12.8 to 13.4,

I checked the ground from engine to frame to battery. Consistently good.

Checked voltage from battery through master switch to breaker. All consistently within .1 volt.

Checked alternator and found field resistance outside parameters set out by Mike Busch. Removed alternator and bench checked. Alternator guru found intermittent field resistance glitch possibly brought on by brushes not seating squarely on rings due to bearing wobble. He rebuilt alternator with good housing, new bearings, brushes, etc. Problem persists with voltage sitting at 13.3 to 13.4 (at least for now).

It appears that the problem is in the voltage regulator. (I say appears, since I have been wrong at every step so far.)

On a M20K (serial no. 25-0686), how does one determine what regulator the plane has. The parts manual lists only one part number (800270-505), and the general heading in the electrical power section, it only says it uses "a transistorized voltage regulator...".

However, in the maintenance section, it says that the "Electro Delta" regulator can be adjusted. Then it says "No field adjustment authorized for Mooney Voltage Regulator".

It doesn't help that the plane seems to be built around regulator. It appears that there are two screws from the outside skin of the plane into the right side of a horizontal plate on which the regulator seems to sit. (You can see a small corner of the regulator from below) The left side of that horizontal plate is riveted onto a slide rail for the transponder(?). How on earth are you supposed to access this thing.

All help so far appreciated. All future comments as well.

Don

[laytonl]

Don, we've all been wrong on this problem. Bottom line is a voltage regulator is relatively cheap so it maybe worth changing out. Zeftronic should be able to tell you which unit you need. My voltage regulator has been replaced before and was not put back in the "hell hole" on the side. I recommend you don't put the new unit back in there. The zeftronics regulators have the correct cannon plug so it should be a "plug n'play". Lee

[DonMuncy]

Thanks again for all the help. It is all fixed now. New Zeftronics voltage regulator, and the voltage is 14v.

I don't mind the alternator work, as it obviously had some problems, which are now repaired.

I don't even mind all the work, since my time is worth about 10 cents an hour.

Plus the educational value is quite high.

[carusoam]

So is it too late to visit NJ?

Best regards,

-a-

[DonMuncy]

We will reschedule our NJ trip, but not in the next week or so.