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Rotax 912 Tachometer Problems

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David X

Joined: 10 Jan 2006
Posts: 154
Location: Princeton, NJ, USA

Posted: Thu Jul 27, 2006 1:40 pm Post subject: Rotax 912 Tachometer Problems

An Aviasport tach (connected to electronic ignition) that was working fine, but then started to act erratic and finally reads zero. I replaced the tach with a new one with no success.



I did a search of the archive on this topic and found one reference to http://www.sportflight.com/kfb/kitfoxsafe.htm ... but that's a dead link now.



Anyone have a source they can point me to in order to help diagnose / fix this problem?



Thank you in advance.

_________________
Zodiac 601 XL - CZAW Built - Rotax 912S
DO NOT ARCHIVE

Last edited by David X on Thu Jul 27, 2006 3:50 pm; edited 1 time in total

NYTerminat(at)aol.com
Guest

Posted: Thu Jul 27, 2006 2:24 pm Post subject: Rotax 912 Tachometer Problems

David,

  

 The pickup for the tach signal puts out an AC voltage. You can look in your  Rotax manual to see what it is supposed to be. I would hook up an AC Voltmeter,  connect one lead from your pickup coil output on your engine and the other to  ground. If you are getting the specified voltage, you have a wire problem from  there to your tach. 

  

  Bob  Spudis

N701ZX 

CH701/912S

do not archive



  

  

 In a message dated 7/27/2006 5:44:20 P.M. Eastern Daylight Time,  dxj(at)comcast.net writes:

  	  Quote: 	
		  An    Aviasport tach that was working, but then started to act irratic and finally    reads zero. I replaced the tach with a new one with no  success.

NYTerminat(at)aol.com
Guest

Posted: Thu Jul 27, 2006 2:49 pm Post subject: Rotax 912 Tachometer Problems

David,

  

 Sorry I ran my mouth before putting my mind in  gear. There are two wires from the tach pickup coil. One of them should be  grounded and the other goes to your tach input. You can disconnect both at the  connector on your engine and connect your voltmeter to both leads to check the  output while the engine is running. Also you can check the other side of the  connector and see if the lead that is supposed to be grounded, really is. You  might have a bad connection on the ground for the pickup coil. You can also  connect an ohmmeter on the two pickup leads to see if there is an open condition  on the pickup side( this is done while the engine is off!). My guess is that you  have a ground or wiring problem, especially since you said it was erratic and  the other tach didn't work. Not likely the pickup  coil. 

  

  

  

  

 In a message dated 7/27/2006 6:25:53 P.M. Eastern Daylight Time,  NYTerminat(at)aol.com writes:

  	  Quote: 	
		        David,

    

   The pickup for the tach signal puts out an AC voltage. You can look in    your Rotax manual to see what it is supposed to be. I would hook up an AC    Voltmeter, connect one lead from your pickup coil output on your engine and    the other to ground. If you are getting the specified voltage, you have a wire    problem from there to your tach. 

    

      Bob    Spudis

N701ZX 

CH701/912S

do not archive



    

    

   In a message dated 7/27/2006 5:44:20 P.M. Eastern Daylight Time,    dxj(at)comcast.net writes:

    	  Quote: 	
		  An      Aviasport tach that was working, but then started to act irratic and finally      reads zero. I replaced the tach with a new one with no    success.

David X

Joined: 10 Jan 2006
Posts: 154
Location: Princeton, NJ, USA

Posted: Thu Jul 27, 2006 6:47 pm Post subject: Re: Rotax 912 Tachometer Problems

Thank you ... very helpful.

_________________
Zodiac 601 XL - CZAW Built - Rotax 912S
DO NOT ARCHIVE

321PT

Joined: 23 May 2006
Posts: 40
Location: Texas

Posted: Fri Jul 28, 2006 5:37 am Post subject: Rotax 912 Tachometer Problems

Am I missing something?  You guys have some good info on problems, so why would you put "Do not archive" on your messages?  Being an old fart, I am not going to be able to remember all this info on the top of my head.  Doesn't the DNA stop anyone from finding it later?

 Or maybe I just don't understand all this new fangled stuff.

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Fri Jul 28, 2006 5:42 am Post subject: Rotax 912 Tachometer Problems

It sure sounds like the effects  of a wire chafing on a ground somewhere.

  

  

 

Noel [quote]   

   --

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

David X

Joined: 10 Jan 2006
Posts: 154
Location: Princeton, NJ, USA

Posted: Fri Jul 28, 2006 7:52 pm Post subject: Re: Rotax 912 Tachometer Problems

I can't speak for others, but I use "DO NOT ARCHIVE" because of what happened to a late friend of mine who was killed in a Zodiac. The newspapers quoted all sorts of things out of context about him and thus maligning him, home-builds and experimentals in general. It seems that they got the info from an archive of this forum. 



 	  321PT wrote: 	
		  Am I missing something?? You guys have some good info on problems, so why would you put "Do not archive" on your messages?? Being an old fart, I am not going to be able to remember all this info on the top of my head.? Doesn't the DNA stop anyone from finding it later?

 Or maybe I just don't understand all this new fangled stuff.

 ?

_________________
Zodiac 601 XL - CZAW Built - Rotax 912S
DO NOT ARCHIVE

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Sat Jul 29, 2006 7:23 am Post subject: Rotax 912 Tachometer Problems

When posting I generally forget to put in the do not archive statement.  I

can see how there are several posts that are either comments or observations

that are not important enough to archive and the no not archive statement

should be used.  For the other 99% of the posts I think we can overlook the

DNA 



Noel



[quote] --

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

David X

Joined: 10 Jan 2006
Posts: 154
Location: Princeton, NJ, USA

Posted: Tue Aug 01, 2006 3:06 pm Post subject: Re: Rotax 912 Tachometer Problems

That was it ... a busted ground wire. Thank you for the helpful replies.



 	  Float Flyr wrote: 	
		  It sure sounds like the effects  of a wire chafing on a ground somewhere. 	




 	  NYTerminat(at)aol.com wrote: 	
		  There are two wires from the tach pickup coil. One of them should be  grounded and the other goes to your tach input. You can disconnect both at the  connector on your engine and connect your voltmeter to both leads to check ...

_________________
Zodiac 601 XL - CZAW Built - Rotax 912S
DO NOT ARCHIVE

NYTerminat(at)aol.com
Guest

Posted: Tue Aug 01, 2006 6:49 pm Post subject: Rotax 912 Tachometer Problems

David,

 Glad that you found and solved the problem

  

 Bob Spudis

  

  

  

 In a message dated 8/1/2006 7:10:33 P.M. Eastern Daylight Time,0 dxj(at)comcast.net writes:

 -->0   Zenith-List message posted by: "David X" <dxj(at)comcast.net>



That0   was it ... a busted ground wire. Thank you for the helpful0   replies.





Float Flyr wrote:

 	  Quote: 	
		   It sure sounds like0the0   effects  of a wire chafing on a ground0   somewhere.


	






NYTerminat(at)aol.com wrote:

 	  Quote: 	
		   There0   are two wires from the tach pickup coil. One of them should be  grounded0   and the other goes to your tach input. You can disconnect both at the 0   connector on your engine and connect your voltmeter to both leads to check ...0   


	




--------

Zodiac 601 XL - CZAW Built - Rotax 912S

DO NOT0   ARCHIVE





Read this topic online0   here:



http://forums.matronics.com/viewtopic.php?p=51625#51625

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