Amp gauge not working and vacuum pressure high

[N9434V]

1970 m20c.    Went to fly today to play with my new garmin gnc355.   Three things amp meter not moving vacuum pressure was high and attitude indicator was a little slow spooling up.       With the help of my a&up friend we looked for the cause of issue.  

1.   Amp gauge    

      a.   Amp gauge has about 2.3 ohms of resistance and does move with external source of voltage. 

      b.   Alternator and regulator are working  confirmed with volt gauge plugged into cigarette lighter     

     c.  One wire to the gauge does indicate battery voltage.   Other wire on gauge does not indicate voltage.    .

     d.  I still need to verify continuity on the second wire,   I am Assuming it goes back to the regulator but have not yet consulted the wiring diagram in my manual

Thoughts?

2.  Vacuum gauge

     a.  Hooked on my mighty vac and pulled 5in and gauge indicated same

     b  visually inspected vacuum lines and all look good with no kinks

Thought?

3.   Attitude indicator     

      Guessing  cool morning and thick grease

 

appreciate any thoughts, direction, other things to check

 

Dennis

 

 

 

 

[carusoam]

Amp gauge... is a volt meter, measuring V drop across a calibrated resistor called the shunt...

Find the two wires going to the shunt, check their fuses...

Both wires will be reading about a nominal 12v...

If one isn’t, check its fuse...

PP thoughts only, not a mechanic... 

Best regards,

-a-

[carusoam]

High vacuum... that’s how our vac pumps work... they get modulated by a regulator...

See why the vac regulator isn’t working as expected...

Your POH probably has a drawing of the vac system showing where all the key parts are...

Review that early on...

PP thoughts only, not a mechanic...

Best regards,

-a-

[N9434V]

Thanks will give those a look

 

[tmo]

7 hours ago, carusoam said:

Both wires will be reading about a nominal 12v...

I always thought one of the wires will be +12V and the other one will go on to the electrical system - IOW, when disconnected from the amp meter, only one of the two wires will be live. Once connected, both terminals should show basically the same voltage, assuming no load, but the "from" wire itself will not be live.

[N9434V]

Carusoam you nailed the ammeter.      I found a wire broken on the end of the fuse holder.  Problem solved

it will be a couple of weeks before I can chase the high vacuum.   Any recommendations on where and for what I should be looking.

I really appreciate the assistance.

Dennis

 

 

 

 

[cctsurf]

2 hours ago, N9434V said:

it will be a couple of weeks before I can chase the high vacuum.   Any recommendations on where and for what I should be looking.

I'd look for a clogged vacuum filter.  Mine goes around the vacuum regulator, which (in my '62) is on the back side of the firewall (toward the passenger compartment).  My vacuum was high and we replaced the filter and now it is much better.

Just thinking about it, I'm curious about all of the filters on the back of the instruments...  They've been there for years, I wonder how they are flowing...  hmmm...  might be worth a check.

James

[Vance Harral]

One possibility on the vacuum regulator is that the tab or safety wire which is supposed to hold the adjusting nut in place has come loose, and the nut has spun all the way in/out/off/whatever to the "unregulated" position.

[jamesm]

I guess my first question on the vacuum system is ....

Has something changed vacuum system configuration? 

Did something new get  installed? 

in Vacuum system  was there a  reason to disconnect the vacuum lines ???

I am real  real embarrassed to admit when I stall my first  G5 ( and my second G5) that I would kept trying to route vacuum  return lines/hook up thinking   that the pneumatic lines should act line a  electric circuit.  After talking to a local instrument repair shop they straighten me out on how pneumatic circuit works. I have was having a similar problem with vacuum regulator, where I was thinking it was thinking it was the  vacuum regulator but mine was on the low side.  if I remember correctly it was vacuum line(s)  connections that I kept trying to  put a return in the pneumatic circuit  to the  pump causing the problem.  Since then I have installed 2  G5's and removed my vacuum system and over period of time.

So with the 2 Garmin  G5's and Tankair 's  electric step conversion on the market..  https://flightenhancements.com/index.html 

There should be  plenty of pre-owned  vacuum pump(s), regulator(s),  vacuum step servo,  vacuum wing leveler servo , and   vacuum pitch servo   for spares parts.

In have a pre-owned/ one time owner/ used Tempest Vacuum pump and/or vacuum regulator, vacuum step servo,  vacuum wing leveler servo , and   vacuum pitch servo.

Also have fairly newly overhauled Vacuum Attitude indicator (I think it was overhauled within the last 5 to 7 years) and DG though cage shaft has cut in it . The set screw head was stripped out. The  DG  still functions when removed.

 

if you are interested.

 

James '67C

[carusoam]

13 hours ago, N9434V said:

Carusoam you nailed the ammeter.      I found a wire broken on the end of the fuse holder.  Problem solved

it will be a couple of weeks before I can chase the high vacuum.   Any recommendations on where and for what I should be looking.

I really appreciate the assistance.

Dennis

 

 

 

 

Thanks for the feed back Dennis!  

I learned a lot around here over the years...

MS is full up with good people.

Best regards,

-a-

[Dreamlifter]

Dennis,

Could you post a panel pic of your GNC355? Do you have an autopilot to couple up with the magic?

Thanks!

[Matt Ward]

Re: the high vacuum, is it consistent throughout flight or only on takeoff / high power settings?  My high vac light will occasionally come on during the takeoff roll but turns off by the time I'm at cruise.  I also have a gauge that shows it just barely out of the green so it's not something I worry about too much.

[N9434V]

I will post some pics of the gnc 355 when I get back to the plane     Hopefully before the end of next week 

 

 

 

[N9434V]

The vacuum pressure was running at almost 6 with full power and was staying high when throttle was pulled back to 1700 rpm