shaking tacho needle ; and alternator intermittent problem

[bavareze]

hi

my tacho has always been shaking but now it started doing it more.  like this - see bellow.

Is this likely to be the cable or the tachomoter?

 

also a new problem just yesterday: suddenly I see the alternator is not charging.  cycle the ATL FIELD switch, nothing.  Then alt off, master off, master on, alt on : charging resumed and ran fine for 10 minutes, then again went to no charge. 

another test:  turning master off , but leaving the alt on in the process, will cause all electrical things to turn off momentarily but then the charging resumed (with the master still off).  so turning the master off caused the alternator to resume charging.

where to start looking?

 

Thanks!

 

 

[N201MKTurbo]

Get an electric tach, your problems will be gone forever. 

[Andy95W]

Your tachometer issue is either gauge, cable, or both.  Rich, above, is right- electronic in this day and age is the way to go.  Instead of throwing 3/4 the cost of a new electronic to replace the mechanical components you have.  A lot of opinions here on which one to get.  I personally installed an UMA TSO'ed tach in mine and think it's great.

What type of alternator system do you have: factory, InterAv, PlanePower?  How old is it?

It sounds like your voltage regulator has gone wonky and/or your overvoltage relay is kicking your system off line when it shouldn't.  This can be caused by bad components or bad connections.  So the first thing to do is clean all connections starting at the battery through the master relay to the bus bar to the master switch, alternator field switch, circuit breaker, voltage regulator, and alternator.

After that, report back if anything changed.  We'll help you spend your money on a new charging system! 

[carusoam]

A) Immediately get new cable... it’s like a bicycle speedometer cable. 

They wear.  Flopping around like that... knocks the needle off when it hits the pin at the end of the arc....

knocking the needle off causes the need to have somebody put it back on.

Can you hear it winding up and making noises?

 

B ) What voltage regulator do you have... Zeftronics is good.  If you have the original sticks, stones and springs Delco model, get a Zeftronics one...  Since you have an alternator, you probably have a newer VR... check the wires for wear and breakage....  look up broken field wire for similar challenges....

Experiences from my M20C...

Best regards,

-a-

[takair]

I have found that tach cable routing can have a huge effect as well.  I have had a simple oil change cause bouncing because I moved the cable from it's optimal routing.  You want the bend radius as broad as possible.  if this does not work, as others have said, it can be cable lube, the cable itself or the tach.  Cold weather compounds all of the above.  Start cheap and check that the routing hasn't been disturbed.

[carusoam]

Adding to the lube idea...

Check the oil cup on the back of the tach. There is actually an oil cup there....

Probably a note in the MM manual to go with that.  What oil, how often.... expect at annual...

 

If you go with a new cable...

Make sure you get the right length, the routing is important...  

Pp thoughts only.

Best regards,

-a-

[bavareze]

so yesterday the tach start shaking much worse and I could hear it doing tic tic tic tic and then suddenly zero!  it died

 

I hope it is the cable this time.

 

battery story did not occur again during 2 hrs flight.  the only difference was yesterday was day and the other day was night. so maybe there is a load issue (more lights at night?)

 

anyways, I will go look to see what kind of regulator I have and start cleaning connections with sand paper.  will post results!

 

Thanks

Radu

[bavareze]

here's the result:

 

the cable is good but the engine side of the end came out of the crimped ending.  I probably need to crimp it again to make it stay.  when I'm putting it back do I use red grease from autozone or something else?

 

electrical: see the last picture where I made a red circle.  that nut was loose to the extent that I could move the wire around and the wire was getting very hot because of that. I guess I need to take it out completely, clean and tighten it properly.  shall I use some battery grease or just dry?  also I see a huge pile of washers used as a spacer but also as an electrical connection, see the yellow circle.  is that ok?

 

I'm also attaching pictures of the rest of the electrical system, maybe you have some input regarding what is good and what is bad.  Had this plane for about 2 years, flew about 200 hrs so far, this is the first set of problems apart from the ones I solved just after buying it.

 

Cheers!

Edited December 7, 2017 by bavareze

[cctsurf]

1 hour ago, bavareze said:

when I'm putting it back do I use red grease from autozone or something else?

Depending on your climate, if you put wheel axle grease or the like in your cable, when it is cold, you will spin the cable into two.  I would suggest speedometer cable lube, but I'm not an A&P.  I hear white lithium grease is good...

[MARZ]

I used to make mechanical speedo / tac cables - the cable end gets squared off with a crimper - special die.  It's very possible the fitting that the cable slides into has been rounded over time.  A reputable speedo shop should be able to help you out.  If the cable had any rust when you pulled it out of the housing consider buying a new assembly. 

[Ned Gravel]

Can you spell EI Tach?  Second set of repairs to mine and the needle was bouncing like it was in its own turbulence.  Fuggedaboudit....... Clarence put one of these in.  Now I can set the governor to within 10 RPM.

[Guest]

On 2017-12-06 at 8:14 PM, bavareze said:

here's the result:

 

the cable is good but the engine side of the end came out of the crimped ending.  I probably need to crimp it again to make it stay.  when I'm putting it back do I use red grease from autozone or something else?

 

electrical: see the last picture where I made a red circle.  that nut was loose to the extent that I could move the wire around and the wire was getting very hot because of that. I guess I need to take it out completely, clean and tighten it properly.  shall I use some battery grease or just dry?  also I see a huge pile of washers used as a spacer but also as an electrical connection, see the yellow circle.  is that ok?

 

I'm also attaching pictures of the rest of the electrical system, maybe you have some input regarding what is good and what is bad.  Had this plane for about 2 years, flew about 200 hrs so far, this is the first set of problems apart from the ones I solved just after buying it.

 

Cheers!

Wow!

I’m not trying to be harsh, but your engine compartment needs some attention.

Wiring is generally in need of replacement more than repairing.

The Adel clamp securing the tach cable is “secured” to the mount with a Tyra’s.

Tyraps on steels tubes is a big no no.

Large wire below the alternator passes thru a clamp with no rubber.

No sealing tapes around the alternator.

Clarence